b5 module introduction - sows - homegrowth+and... · · 2012-06-29b5 module introduction ... by...

OCR 21st Century Science: B5 Growth and development

COLLINS NEW GCSE SCIENCE © HarperCollinsPublishers Ltd 2011

B5 Module Introduction

Pages 38–39 in the Student Book provide an introduction to this module.

When and how to use these pages

These pages summarise what students should already know from previous GCSE modules or from KS3 and

provide an overview of the content that they will learn in this module.

o Use these pages as a revision lesson before you start the first new topic.

o Brainstorm everything that students remember about the different topics using the headings as a starting point. Compare your list with the points on page 38.

o Use the questions on page 38 as a starting point for class discussions.

o Ask students if they can tell you anything about the topics on the right-hand page.

o Make a note of any unfamiliar / difficult terms and return to these in the relevant lessons. Suitable answers to the questions on page 38 are:

o Two of: sperm cell, egg cell, nerve cell, palisade cell, root hair cell / other specialised cell

o Genes: eye colour, natural hair colour, dimples, tongue rolling; environment: tattoos, hair length, scars, piercings; both: height, weight, IQ

You could revisit these pages at the following points:

o Before the lesson on mitosis, pages 52–53

o Before the lesson on cell specialisation and gene activity, pages 60–61

Overview of module

In this module, students will learn about cell specialisation as the basis for differentiation. They will learn how

proteins are coded for by genes which in turn provide the characteristics of the cell. Students will learn what stem

cells are and how they are formed, how stem cells are used in research and that their use in research is restricted

by government regulations as well as ethical implications.

The first topic explains animal and plant development, comparing and contrasting the adaptation of unspecialised

cells in each. Students will consider the ability of plant meristems to regenerate whole plants, and will learn about

the effect of plant hormones on their development.

The second topic looks at the key stages in the cell cycle, and students will compare cell division by mitosis and

meiosis.

In the final topic, students will explore the structure of the genetic code and the process of protein synthesis.

Obstacles to learning

Students may need extra guidance with the following terms and concepts:

Embryo and zygote

There may be some confusion between the terms ‘embryo’ and ‘zygote’; make sure students use the correct

terminology. The fertilised egg cell is referred to as a zygote. Mitotic division results in a two-cell stage (correctly

called a morula). Further mitotic divisions lead to a ball of cells referred to as an embryo.

Stem cells

There are different types of stem cells and students may be confused by the use of the same term ‘stem cell’ to

describe these different types. It is important that students understand the difference between the two types of

human stem cell (adult and embryonic) and understand how both are different from plant stem cells (meristem

cells).

There may be some confusion over the nature of adult stem cells. Some students may think that they are only

found in adults. Adult stem cells are found in umbilical cord blood, in newborn babies, in infants and in growing

children as well as in adults.

Students may associate stem cell research with the well-known picture of the mouse with an ear on its back. This

picture has nothing to do with stem cell research and is actually an example of bio-engineering using polymers and

cow cells. (So far, the only whole organ to be produced from stem cells is the bladder but there have been partial

organs such as skin, parts of the trachea and knee cartilage. Very recently, a human kidney has also been

generated.)

B5 Module Introduction continued


Students tend to think that plant stem cells are very different in function to animal stem cells. This can be dispelled

by asking them to write down the functions of animal stem cells and then plant stem cells, or draw them in a Venn

diagram. They need to realise that both types of stem cell need to remain unspecialised to be able to divide.

Cloning

There are different types of plant cloning techniques, and students may be confused by the use of the term

‘cloning’ to describe the different types. It is important that students understand the difference between the different

types of plant cloning techniques; cuttings are straightforward pieces of plants that are grown to produce a plant;

tissue culture involves pieces of plant tissue divided into cells and grown; meristem culture involves using just

meristem cells from a plant grown to become a full plant.

Plant development

Students often misconceive auxin (a Higher tier requirement) as a single hormone; it needs to be explained that

auxin is the generic name for a class of plant hormones responsible for tissue development.

Mitosis and meiosis

Students may struggle with the difference between mitosis and meiosis. They may have particular difficulty with the

idea that in mitosis the parent cell undergoes one cell division, whereas in meiosis the parent cell undergoes two

cell divisions.

Appearance of chromosomes

You may need to mention the different ways in which chromosomes are drawn. Books often draw chromosomes in

the ‘X’ shape. However, when cells are not dividing, chromosomes look like a single cylinder – this is what the

chromosome looks like before replication.

Proteins

It is necessary that students understand why proteins are important in the cell. They need to understand that all

functions and characteristics of the cell are due to proteins.

Cell specialisation

It is difficult for lower attaining students to understand that the same genes are found in all body cells. They may

find it hard to grasp the idea that some genes are turned off when a cell becomes specialised. An analogy with a

sports shop may help – there are many types of sporting goods available but a shop specialising in football will only

want to display football-related products. The other goods available will be ‘switched off’. Make sure they don’t form

the misconception that these other goods are removed (implying that switched-off genes are removed).

Practicals in this module

In this module students will do the following practical work:

o looking at a variety of animal and plant cells under the microscope or using bio-viewers

o taking plant cuttings

o investigating phototropism in plants

o modelling mitosis

o modelling meiosis

o modelling DNA, genes, chromosomes and proteins

o extracting DNA from bananas

Key vocabulary covered in this module

unicellular �� multicellular �� specialised �� adaptation �� tissue

organ �� organ system �� zygote �� embryo �� differentiation

sex cells �� sperm cells �� egg cells �� fertilisation �� embryonic stem cells �� adult stem cells

palisade cells �� xylem cells �� phloem cells �� meristems

clone �� tissue culture �� auxin (Higher tier)

photosynthesise �� phototropism �� positively phototropic

mitosis �� daughter cells �� meiosis �� gametes

chromosomes �� DNA �� double helix �� bases �� nucleotide �� base pair �� genes �� genetic code

cytoplasm �� membrane �� nucleus �� chromosomes �� ribosomes

amino acids (Higher tier) �� messenger RNA (Higher tier)

switched off genes �� switched on genes �� active genes �� stem cell therapy �� therapeutic cloning



B5 Planning and collecting

Pages 48−49 in the Student Book prepare students for controlled assessment.


This activity provides an opportunity to build and assess the skills that students will use when planning an

investigation.

Ask students to:

o read through the context and tasks, listing any terms that they do not understand

o as a whole class or in small groups, discuss the tasks to ensure that all students understand the terminology used and to clarify what is required

o work individually or in small groups to answer the questions for each task.

If time allows, ask the students to mark one another’s work using the mark scheme provided.

Notes

The purpose of this activity is for students to consider how an investigation should be planned and how evidence

should be collected in such a way as to support the drawing of conclusions. The context provided is that of cloning

plant material. It is not assumed that students will undertake this practical activity (though there are a number of

learning outcomes that would be achieved by so doing) but the focus of the activity is to reflect and comment upon

how Chloe and her group carried it out. This is an effective way of making key points about the development of

these skills on the approach to carrying out centre-marked assignments.

The tasks are progressively more challenging and give access to higher grade outcomes as students proceed

through them.

Answers Task 1

� After 10 days there will have been visible growth of the explant in the growth medium in the tube. If there had

been any contamination there would also be visible growth of microbe colonies.

� The equipment included cauliflower, a knife and cutting board, Milton solution, sterile distilled water, growth

medium, Bunsen burner, sterilised forceps, plug for tube.

Task 2

� The purpose of the techniques was to provide the plant material with appropriate conditions for growth but to

exclude any contamination, such as microbes, which would also grow.

� There is a hazard with using a sharp blade, so they would have to exercise care and follow instructions on how

to cut the material.

Task 3

� They are likely to have predicted that the explant would have grown and developed some of the visible features

of a cauliflower plant. They may also have predicted that their procedures would have prevented any

contamination, but that if such contamination did take place it would also have grown.

� They should have used ideas about the plant cells being totipotent and therefore being able to reproduce all the

features of a plant. They could also have identified that the conditions they set up were optimised for growth,

with a supply of nutrients, warmth, light and moisture.

Task 4

� The procedure would result in growth of the explant with visible features of a complete plant developing. The

procedure would stop other organisms from growing with the use of Milton solution and heat.

� The techniques provided a sterile environment that would encourage rapid growth of the cauliflower and

development of observable characteristics and would prevent other organisms from flourishing under such ideal

conditions.

B5 Planning and collecting continued


� Risk assessment for use of knife: Follow instructions carefully. Use appropriate knife. Cut on a stable and

suitable surface. Carry a knife with the blade pointing downwards. Store knives securely after use. Do not leave

knives loose on the bench. Do not try to catch a falling knife.

Mark scheme

For grade E, students need to:

o Offer a testable prediction for the students and justify it, using relevant scientific terms.

o Identify equipment the students could use to collect data

o Identify and comment on hazards they encountered.

For grades D, C, in addition they need to:

o Identify major factors and scientific knowledge the students should use to make a testable hypothesis.

o Suggest techniques and equipment the students should use which are appropriate for the range of data required.

o Identify any significant risks for the students and suggest some precautions.

For grades B, A, in addition they need to:

o Suggest what the students could investigate and propose a testable hypothesis.

o Suggest equipment and techniques the students should use to achieve precise and reliable data. Produce a full and appropriate risk assessment.



B5 Exam-style questions

Pages 66-67 in the Student Book are exam-style questions.


These questions are based on the whole of Module B5 and cover a range of different types of questions that

students will encounter in their written exams.

o Questions could be used as a revision test once you’ve completed the module.

o Work through the questions as a class as part of a revision lesson.

o Ask students to mark each other’s work, using the mark scheme provided.

o As a class, make a list of the questions that most students did not get right. Work through these as a class.

Notes on the worked examples

The first example looks at why phototropism is important for plants. To gain full credit, students need to know how

phototropism can place a plant at an advantage when competing for light and other resources.

The second example is a 4-mark question requiring a justification for the response. Students need to show

knowledge of cell specialisation and also an ability to evaluate statements about gene activation. Students should

also use the scientific terms appropriate to this topic to score full marks.

Assessment Objectives

These exam-style questions cover the Assessment Objectives as described below.

Assessment Objectives Questions

AO1 Recall, select and communicate their knowledge and understanding of science

1, 3c, 4

worked example 1

AO2 Apply skills, knowledge and understanding of science in practical and other contexts

2, 3a, 3b, 5, 6

AO3 Analyse and evaluate evidence, make reasoned judgements and draw conclusions based on evidence

7

worked example 2

Answers

These answers are also supplied on the Teacher Pack CD so that students can mark their own, or their peer’s

work.

Question

number

Answer Additional notes Marks

1 Four

Double

2

2 B Seed coat 1

3a The cells have become specialised 1

3b Genes code for protein/milk

Genes in other cells are switched off

2

3c A False

B False

C True

D True

2 marks for all four correct

1 mark for two or three correct

2

B5 Exam-style questions continued


4 Could include the following points:

Cells divide/split

Mitosis occurs

Detail of mitosis

Cells enlarge / get bigger

Some cells stay as stem cells

Differentiation occurs/cells become

specialised

4 marks: answer describes

correctly the events that occur in

growth and development,

incorporating at least four of these

points


correctly an aspect of growth or

development, incorporating at

least three of these points


correctly an aspect of growth or

development, incorporating at

least two of these points

1 mark: one of these points is

described correctly

4

5 There is no harm/damage to the embryo 1

6a 4-2-4-1 All four correct; correct order 2

6b 3-2-4-2 All four correct; correct order 2

6c One 1

7 Jo and Ray

Justification: Meiosis produces four

gametes with 23 chromosomes each

because fertilisation involving two

gametes will result in the zygote having

the full chromosome number of 46

2 marks: both correct in either

order

2 marks: or words to this affect

4



B5 Module Checklist

Pages 64-65 in the Student Book provide a student-friendly checklist for revision.


This checklist is presented in three columns showing progression, based on the grading criteria. Bold italic means

Higher tier only.

Remind students that they need to be able to use these ideas in various ways, such as:

o interpreting pictures, diagrams and graphs

o applying ideas to new situations

o explaining ethical implications

o suggesting some benefits and risks to society

o drawing conclusions from evidence they have been given.

These pages can be used for individual or class revision using any combination of the suggestions below.

o Ask students to construct a mind map linking the points on this checklist.

o Work through the checklist as a class and note the points that need further class discussion.

o Ask students to tick the boxes on the checklist worksheet (on the Teacher Pack CD) if they feel confident that they are well prepared for the topics. Students should refer back to the relevant Student Book pages to revise the points that they feel less confident about.

o Ask students to use the search terms at the foot of the relevant Student Book pages to do further research on the different points in the checklist.

o Students could work in pairs, and ask each other what points they think they can do, and why they think that they can do those, and not others.

B5 Module Checklist continued


Module summary

In the introduction to this module, students were presented with a number of new ideas. Work through the list

below as part of their revision. Ask students to write their own summaries and mind maps, using this list as a

starting point.

Cell specialisation

o Cells in multicellular organisms can be specialised to do particular jobs

o Groups of specialised cells are called tissues

o Cells in a human embryo at the eight-cell stage are all able to become any type of cell required by the organism

o After the eight-cell stage, most embryo cells become specialised

o Some cells remain unspecialised and can become specialised at a later stage to become many but not all types of cell

Stem cells in animals

o There are two types of stem cells in animals

o Adult stem cells can produce a limited number of types of cell

o Embryonic stem cells can produce any type of cell

Stem cells in plants

o In plants, only cells within special regions called meristems are able to divide

o Cells from the meristem region are unspecialised and can develop into any plant cell

o Unspecialised plant cells can become specialised to form different types of tissue

Plant development

o The growth and development of plants is affected by the environment

o For example, they have a growth reposnse towards light called phototropism

Cell cycle and protein synthesis

o DNA has a double helix structure and both strands of the DNA molecule are made up of four different bases

o The order of bases in a gene is the genetic code for the production of a protein

o The genetic code is in the cell nucleus of animal and plant cells but proteins are produced in the cell cytoplasm

o Genes do not leave the nucleus but a copy of the gene is produced to carry the genetic code to the cytoplasm

o The main processes of the cell cycle include a) cell growth during which numbers of organelles increase and chromosomes are copied, and b) mitosis during which copies of the chromosomes separate and the nucleus divides



Checklist B5 Aiming for A

Use this checklist to see what you can do now. Refer back to pages 40–63 if you’re not sure. Look across the rows to see how you could progress – bold italic means Higher tier only.

Remember you’ll need to be able to use these ideas in many ways:

� interpreting pictures, diagrams and graphs � applying ideas to new situations � explaining ethical implications � suggesting some benefits and risks to society � drawing conclusions from evidence you’ve been given.

Look at pages 300–306 for information about how you’ll be assessed.

Working towards an A grade

Aiming for Grade C �� Aiming for Grade A �� recall that a fertilised egg cell (zygote) divides by mitosis to form an embryo; recall that up to the eight-cell stage the cells of an embryo are unspecialised and identical (embryonic stem cells)

understand that adult stem cells can become specialised at a later stage to become many, but not all, types of cell required by the organism

explain the characteristics of specialised and unspecialised cells

understand that the new cells produced from plant meristems are unspecialised and can develop into any kind of plant cell

explain how phototropism increases the plant’s chance of survival

explain phototropism in terms of the effect of light on the distribution of auxin in a shoot tip

describe the main processes of the cell cycle; explain the characteristics of parent and daughter cells; understand why, in meiosis, it is important that the cells produced only contain half the chromosome number of the parent cell

understand that the order of bases in a gene is the genetic code for the production of a particular protein

explain how the order of bases in a gene is the code for building up amino acids in the correct order to make a particular protein

understand that genes do not leave the nucleus, but a copy of the gene (messenger RNA) is produced to carry the genetic code to the cytoplasm

explain how messenger RNA is used to carry the genetic code to the cytoplasm

understand that adult stem cells and embryonic stem cells have the potential to produce cells needed to replace damaged tissues

understand that in carefully controlled conditions of mammalian cloning it is possible to reactivate inactive genes in the nucleus of a body cell

OCR 21st Century Science: B5 Checklist


Aiming for Grade C �� Aiming for Grade A �� understand that although all body cells in an organism contain the same genes, many genes in a particular cell are not active (are switched off) because the cell produces only the specific proteins it needs

understand that in specialised cells only the genes needed for the cell can be switched on, whereas in embryonic stem cells any gene can be switched on during development to produce any type of specialised cell



b5_01 How do organisms develop?

Resources

Student Book pages 40–41 � Interactive Book: Quick starters ‘Adaptations of a leaf’, ‘Specialised cells’, ‘Cell division’

Homework pack b5_01

Files on Teacher Pack CD: b5_01_worksheet

Pictures of different animal cells (keep these simple to recap KS3 teaching); microscopes or bio-viewers and slides of different animal cells; models, animations/PowerPoints/videos about cell division

Learning outcomes B5.1.1 recall that cells in multicellular organisms can be specialised to do particular jobs

B5.1.2 recall that groups of specialised cells are called tissues, and groups of tissues form organs

B5.1.3 recall that a fertilised egg cell (zygote) divides by mitosis to form an embryo

Literacy focus: Working in pairs/as individuals to write descriptions of different specialised cells.

ICT focus: Viewing images, video clips and animations of cell specialisation.

In this lesson students are learning to:

� understand that cells in multicellular organisms can be specialised to do a particular job

� describe what tissues and organs are

� understand that specialisation of cells changes them to become any type of cell required by the organism

Key vocabulary

unicellular �� multicellular �� specialised �� adaptation �� tissue

organ �� organ system �� zygote �� embryo �� differentiation


There may be some confusion between the terms ‘embryo’ and ‘zygote’; make sure students use the correct

terminology. The fertilised egg cell is referred to as a zygote. Mitotic division results in a two-cell stage (correctly

called a morula). Further mitotic divisions lead to a ball of cells referred to as an embryo.

Stimuli and starter suggestions

� Show students pictures of different cells (red blood cell, muscle cell, sperm cell, egg cell, white blood cell, nerve

cell, bone cell). Get them to name the cells and encourage students to explain what job each cell does.

Learning activities worksheet b5_01 Low demand � Ask students to name some of the organs they know, including what jobs these organs can carry

out. The key points that need to be developed are that organs carry out particular functions and work together as

part of organ systems. Between them, organ systems carry out the seven processes of life. Students complete

worksheet activity 1.

Students can look at a variety of cells under the microscope or using bio-viewers. Try to help students understand

that actual cells may look different from diagrams in textbooks because of the magnification, as well as the way the

specimen has been sectioned and dyed.

Teaching and learning notes: For activity 1, more able students can be encouraged not to use the words in the

box but only to refer to them for help. They could add other organs from that organ system to the last column.

Standard demand � Show students available resources (e.g. models, animations) about cell division. Make sure

students understand that the two keypoints; 1. cells in mitotic division are identical to parent cells and 2. that the

genetic material in the nucleus remains the same. Use questioning to elicit these points. Students complete

worksheet activity 2.

Teaching and learning notes: How students are shown cell division depends upon the resources available.

These could be a series of PowerPoint slides, a video clip, an animation, a series of diagrams on card or a model.

b5_01 How do organisms develop? continued


High demand � Use the Student Book p. 5 to lead into a discussion about the switching on and off of genes. Use

search terms ‘video + switching genes on and off’ to help illustrate that although two organisms may both possess

the same gene linked to a particular trait, this trait may not be expressed unless the gene is turned on. This is done

by an enhancer, a piece of noncoding DNA (previously thought of as ‘junk’ DNA) that acts as a ‘switch’. Students

can then do activity 3 on the worksheet.

Teaching and learning notes: Ask students to think of an analogy to model this process of gene regulation. An

effective analogy to model the switching on and off of genes could be the mixing of colours – for example, to make

the colour green in a paint shop, the yellow and blue paints are turned on but the red is turned off. Similarly, to

make a cell that is able to contract, the genes that make the protein myosin need to be turned on.

Plenary suggestions Students write in ten words what they have learned today and share these with a partner or group. Choose

students for feedback and to make sure that responses are correct. If there is time, open the discussion to the

rest of the group.

Student Book answers Q1 Cells, tissue, organs, organ systems, whole body

Q2 Because they carry out different jobs.

Q4 A zygote grows by dividing/cell division.

Q5 A specialised cell is adapted/differentiated to carry out a particular function. For example, a red blood cell is

adapted to carry oxygen around the body.

Q6 Different genes in the muscle cell are turned on/off than in a kidney cell.

Q7 Genes to make a nucleus, produce antibodies, allow the cell to change shape, produce lots of mitochondria

Worksheet answers Activity 1 (Low demand)

Q1 Digestive – digests and absorbs food – stomach, liver, pancreas, intestines

Breathing – exchanges gases – lungs, windpipe

Reproductive – produces new organisms – ovaries, uterus, testes

Nervous – responds to the environment – brain, spinal cord

Circulation – transports substances – heart, arteries, veins

Q2 Muscle cell – can contract

Red blood cell – has a large surface area

Sperm cell – can swim

White blood cell – can change shape to surround bacteria

Activity 2 (Standard demand)

Q1 Diagrams should show a zygote divided into two cells, then four cells and then eight cells.

Q2 Answers for red blood cells could include no nucleus; no mitochondria; round shaped; biconcave shaped; filled

with haemoglobin; carrying oxygen. Answers for white blood cells could include irregular shape; large nucleus;

bi-lobed nucleus; cytoplasm full of organelles; attacks microorganisms; produces antibodies.

Activity 3 (High demand)

Q1 Genes ON for the characteristics described above in activity 2. Genes OFF could be any (sensible suggestion)

such as secreting hormones; having a tail, having cilia, etc.

Q2 Genes ON could include: elongated shape; single nucleus’ ability to contract; striations.

Genes OFF could be any (sensible suggestion) such as: secreting hormones; having a tail, having cilia, etc.



b5_01 How do organisms develop?

1 Cell adaptations

1 Complete the table using the correct words from the box below.

Organ system Function Organs

digestive

breathing

reproductive

nervous

circulatory

Functions: responds to the environment, exchanges gases, transports substances,

produces new organisms, digests and absorbs food

Organs: stomach, heart, liver, intestines, ovaries, arteries, uterus, veins, pancreas,

testes, brain, lungs, spinal cord, windpipe

2 Match the adaptation to the cell:

Cell Adaptation

can swim

has a large surface area

can change shape to surround bacteria

can contract

b5_01 How do organisms develop? continued


2 Cell specialisation

1 In the space below draw a series of diagrams to show how a zygote reaches the eight-cell stage.

2 Create a table comparing the structure and function of a red blood cell and a white blood cell.

3 How cells differentiate

1 Write down which genes are switched on and which genes are switched off in red blood cells and in white blood cells. An example is given below:

In a red blood cell, genes for making mitochondria are switched off.

2 Find out about the structure and function of muscle cells. Use what you have learned to write down which genes are switched on and which ones are switched off in a muscle cell.



b5_02 Stem cells

Resources

Student Book pages 42–43 � Interactive Book: iCould career video ‘Stem cells’ � Homework pack b5_02


Animations/videos of fertilisation

Learning outcomes B5.1.4 recall that in a human embryo up to (and including) the eight cell stage, all the cells are identical

(embryonic stem cells) and could produce any type of cell required by the organism

B5.1.5 understand that after the eight cell stage, most of the embryo cells become specialised and form different

types of tissue

B5.1.6 understand that some cells (adult stem cells) remain unspecialised and can become specialised at a later

stage to become many, but not all, types of cells required by the organism

ICT focus: Viewing images, video clips and animations of cell fertilisation.


� recall that in a human embryo up to the eight-cell stage, all the cells are identical

� understand that after the eight-cell stage, most of the embryo cells become specialised and form different types

of tissue

� understand that some cells remain unspecialised until a later stage

Key vocabulary

sex cells �� sperm cells �� egg cells �� fertilisation �� zygote �� embryo

embryonic stem cells �� adult stem cells


There may be some confusion over the nature of adult stem cells. Some students may think that they are only

found in adults. Adult stem cells are found in umbilical cord blood, in newborn babies, in infants and in growing

children as well as in adults.

Students may also associate stem cell research with the well-known picture of the mouse with an ear on its back.

This picture has nothing to do with stem cell research and is actually an example of bio-engineering using polymers

and cow cells. So far, the only whole organ to be produced from stem cells is the bladder but there have been

partial organs such as skin, parts of the trachea and knee cartilage. Very recently, a human kidney has also been

generated.


� Show students pictures from the internet of a bladder grown in a lab (use search terms ‘bladder + stem cells’

in Google images) and start a discussion of what a bladder is and what its function is. Then introduce the idea

that this bladder has been grown from a few cells. This should help students understand that stem cells can be

grown into any type of cell. With a more able class, perhaps thinking about the different kinds of tissues needed

to make the bladder could lead to the idea of genes being switched on (from the previous lesson). This could

lead on to the reasons why having organs from your own stem cells is better than using organs from other

people’s stem cells.

Learning activities worksheet b5_02 Low demand � Show students an animation of the process of fertilisation. Using the cards provided on the

worksheet, ask students to do a card-sort activity where they arrange pictures of egg and sperm, then zygote and

then successive numbers of cells up to an eight-cell embryo. They should label each stage.

Teaching and learning notes: Using the internet or pictures from books, students can look at a variety of cells

such as sex cells, zygotes, embryos and stem cells.

Standard demand � Ask students to use the Student Book pp. 42–43 to make a table comparing embryonic stem

cells and adult stem cells. Make true and false statements about stem cells and Use ‘traffic light’ cards to assess

their learning. Students can then complete worksheet activity 2.

b5_02 Stem cells continued


Teaching and learning notes: The traffic light cards will help formative assessment – go back over the key terms

if students are not sure.

High demand � Use the Higher section in the Student Book p. 43 to lead into a discussion about the importance of

stem cells. Elicit ideas about why they are important using ideas already covered in the Student Book as well as

other ideas that students may have encountered in earlier modules or during internet research. Encourage

students to think about all the diseases they know of that can be treated with stem cell therapies. Worksheet

activity 3 is a research task.

Teaching and learning notes: Ask students to think about other uses of tissues created by stem cells, apart from

the obvious one of replacing damaged or diseased tissue. Looking at the effects of new drugs on tissues and

organs, as well as understanding the causes of birth defects, are other not so obvious advantages.

Plenary suggestions Students could produce a leaflet for a maternity hospital notice board, advising mothers about the advantages of

donating stem cells from the umbilical cords left over from the birth of their babies.

Student Book answers Q1 Fertilisation

Q2 Zygote

Q3 Embryonic stem cells come from embryos and can differentiate into any type of cell. Adult stem cells come from

certain organs such as bone marrow and can only differentiate into certain types of cell.

Q4 No – they can only become blood cells.

Q5 Stem cells can differentiate into different cells found in the body.

Q6 Stem cells can differentiate into cells of different tissues to form an organ. These organs could be used in

transplantation operations.


Q3 a) False – Fertilisation is an example of sexual reproduction.

b) False – The sperm cell comes from the male and the egg cell comes from the female.

c) True

d) False – The fertilised egg cell is called a zygote.

e) True


Drawings should show 1) zygote (for embryonic stem cells) and 2) bone, blood or umbilical cord (for adult stem

cells).



b5_02 Stem cells

1 Fertilisation

1 Cut out the cards at the bottom of the sheet. Put them in the correct order, stick them on a sheet of paper, and add labels and arrows to show the process of fertilisation.

2 Complete this diagram showing fertilisation and add the missing words.

3 Circle the letter of the statements that are true. Correct the false ones.

a) Fertilisation is an example of asexual reproduction.

b) The sperm cell comes from the female and the egg cell comes from the male.

c) The joining of the nucleus of the sperm and egg cell is called fertilisation.

d) The fertilised egg cell is called an embryo.

e) The embryo cells divide many times to eventually develop into a whole organism.

b5_02 Stem cells continued


2 What are stem cells?

1 Draw a diagram in the space below to show where adult stem cells and embryonic stem cells come from. You may find it useful to refer to your textbook.

2 Now draw some diagrams to show examples of the kind of specialised cells these stem cells can become.

3 The importance of stem cells

Use the internet to find out more about stem cell treatments and make a list of all the possible potential treatments. How many of these treatments are currently available?



b5_03 Stem cells in plants

Resources

Student Book pages 44–45 � Interactive Book: Drag and drop ‘Cells and specialisation’ � Homework pack b5_03


Bio-viewers or microscope and slides of different plant cells; images, video clips and animations of stem cells in plants

Learning outcomes B5.1.7 understand that in plants, only cells within special regions called meristems are mitotically active

B5.1.8 understand that the new cells produced from plant meristems are unspecialised and can develop into any

kind of plant cell

B5.1.9 understand that unspecialised plant cells can become specialised to form different types of tissue

(including xylem and phloem) within organs (including flowers, leaves, stems and roots)

ICT focus: Viewing images, video clips and animations of stem cells in plants.


� understand the different types of tissue within organs of a plant

� understand that in plants, only cells within special regions can divide

� understand that plants also have stem cells

Key vocabulary

palisade cells �� xylem cells �� phloem cells �� meristems


Students tend to think that plant stem cells are very different in function to animal stem cells. This can be dispelled

by asking them to write down the functions of animal stem cells and then plant stem cells, or draw them in a Venn

diagram. They need to realise that both types of stem cell need to remain unspecialised to be able to divide.


� Show students pictures of a plant and get them to name the organs they can see. Compare these organs with

the organs of an animal. Students should be introduced to the idea that, just like animal organs, plant organs are

made of multiple types of tissue. This should lead into the introduction of different types of plant cells such as

palisade cells, xylem cells and phloem cells. Students may remember root hair cells from KS3, in which case

allow them to talk about structural adaptations.

Learning activities worksheet b5_03 Low demand � Show students bio-viewer or microscope slides of different plant cells. Ask students to draw the

different cells they see. Discuss their structures and functions. Ask students to label their diagrams and add further

notes to make graphic organisers detailing the information.

Students can also do activity 1 on the worksheet.

Teaching and learning notes: Using the slides, students can look at a variety of cells such as palisade, xylem,

phloem, root hair and spongy cells. Make sure they understand which cell they are seeing and which organ of the

plant each belongs to.

Standard demand � Using the Student Book p. 44–45, ask students to describe and compare the different plant

cells they know about. Use questioning to assess learning.

Students can then complete activity 2 on the worksheet, the first task of which involves pair/group discussion about

the adaptations of specialised plant cells.

Teaching and learning notes: Questioning with increasingly complex questions will help formative assessment –

go back over key ideas if students are not sure. Suitable starter (easier) questions could be: What does the

palisade cell do? What does the xylem cell look like? Questions should gradually become harder: What is the

difference between a palisade cell and a root hair cell? Why? What is the difference in their functions? (Eliciting the

idea that one has chloroplasts and the other doesn’t.)

b5_03 Stem cells in plants continued


High demand � Students should use books, the internet or other resources that show where the meristem tissue

can be found. They should find out that, as well as roots and shoots, apical buds have meristem cells. These are

the dominant buds found at the top of the plant.

Encourage students to think about the differences between animal and plant stem cells.

They can use activity 3 on the worksheet to guide them in this work.

Teaching and learning notes: With more able students, it is desirable for them to know exactly where meristem

tissue is found – make sure they know the less obvious parts, such as apical buds.

Plenary suggestions Students present their findings from the different activities to their peers. Presentations should be worked on in

groups and can be given either by the whole group or by an ‘expert’ representative from each group. The key

points to focus on are:

• Plants also have stem cells that can specialise into any type of cell.

• Plant stem cells are found in areas called the meristem regions.

• Some students may be able to name the parts of the plant where the meristem regions are found.

Student Book answers Q1 They contain lots of chloroplasts for photosynthesis.

Q2 Phloem cells have holes in their end walls so substances can flow through. They stand end to end like a straw

to help the flow of substances.

Q3 The cells in the meristems

Q4 No – only cells that are undifferentiated are able to divide.

Q5 Various answers; should include the point that plants make their own food and stay in one place in the ground –

but do not accept ‘cannot move’.


Q1 Palisade cell – produces food for the plant

Xylem cell – carries water and minerals

Phloem cell – carries glucose and other substances

Q2


Q2 Students’ own diagrams. One path leads to cell specialisation; the second to further cell division.


Q1 Should include roots, shoots and apical buds.

Q2 Both types can follow one of two routes: cell specialisation or further division. Both can turn into any type of cell.

Some reference to genes switching off in specialised cells or lack of division after specialisation. Some idea that

plant cells are able to regenerate if the plant is damaged.



b5_03 Stem cells in plants

1 Plant cells

1 Draw lines to match each of the plant cells to its function.

palisade cell carries glucose and other substances

xylem cell produces food for the plant

phloem cell carries water and minerals

2 Label the parts of the palisade cell shown below using the words from the box.

vacuole cell wall nucleus chloroplasts cell membrane cytoplasm

2 Cell division in plants

1 In groups or pairs, discuss how palisade cells, xylem cells and phloem cells are adapted to their functions. Share your findings with another group.

2 Draw a diagram showing the two routes that the daughter cells of a newly divided plant cell may follow.

3 Cell specialisation in plants

1 Draw a diagram showing all the parts of a plant that contain meristems.

2 Compare and contrast animal stem cells with meristem cells.

3 Find out about the two types of meristem and their roles in plant growth. Share your findings with a partner.

4 Carry out your own research on the internet to find out how the rare lady’s slipper orchid is being reintroduced at Kew Gardens.



b5_04 Plant clones

Resources

Student Book pages 46-47 � Interactive Book: Matching pairs ‘Plant tissues’ � Homework pack b5_04

Files on Teacher Pack CD: b5_04_practical; b5_04_technician

Video clip of binary fission of bacteria (to be used when explaining cloning of plant cells and the idea of genetic clones); equipment for practical

Learning outcomes B5.1.10 understand that the presence of meristems (as sources of unspecialised cells) allows the production of

clones of a plant from cuttings, and that this may be done to reproduce a plant with desirable features

B5.1.11. understand that a cut stem from a plant can develop roots and then grow into a complete plant which is a

clone of the parent, and that rooting can be promoted by the presence of plant hormones (auxins)

Ideas about Science IaS 6.4 some questions, such as those involving values, cannot be answered by science


� explain how plant clones are made

� explore some of the ways plants can be cloned

Key vocabulary

clone �� tissue culture �� auxin (Higher tier only)


There are different types of plant cloning techniques, and students may be confused by the use of the term

‘cloning’ to describe the different types. It is important that students understand the difference between the different

types of plant cloning techniques; cuttings are straightforward pieces of plants that are grown to produce a plant;

tissue culture involves pieces of plant tissue divided into cells and grown; meristem culture involves using just

meristem cells from a plant grown to become a full plant.

Students often misconceive auxin (a Higher tier requirement) as a single hormone; it needs to be explained that

auxin is the generic name for a class of plant hormones responsible for tissue development.


� Show a video or animation about plant cuttings. Brainstorm what the students currently know about cloning, and

try to clear up misconceptions that may arise as they try to compare plant clones with animal clones that they

studied in B1.

Learning activities practical sheet b5_04 Low demand � This lesson aims to develop students’ understanding of the fact that plants are able to reproduce

asexually – that is, produce clones of themselves. Students will have an opportunity to clone plant material. Show a

video clip of cuttings dipped in rooting powder and elicit ideasa about why this step is important.

Standard demand � The main part of this lesson is a practical activity in which students take cuttings of plants

(see practical sheet b5_04). Showing students how straightforward it is to clone a plant may help ideas about the

asexual reproduction of plants to be better recalled. It is important to draw out how reproducing asexually can be

an advantage or disadvantage to the plant, depending on the situation and the habitat in which it finds itself.

Cloning is most successful if the environment is very stable. Ask students to explain why this is. Use Student Book

pp. 46–47 and ask students to answer the questions while waiting for the water to soak. See also technician sheet

b5_04.

Teaching and learning notes: Talk through the safety procedures and the steps of the practical before they start

the practical work. Knives are required. Use your judgement about whether or not this is suitable for a class

practical; if in doubt, demonstrate.

High demand � It is theoretically possible to produce plantlets using meristem culture with the higher ability

students. Appropriate protocols can be found on the internet particularly, the SAPS website. If conditions are made

as aseptic as possible, it is possible to gain a degree of success in this practical.

b5_04 Plant clones continued


Plenary suggestions Get a volunteer to come to the front of the class and to choose an area of the lesson they feel confident about. Ask

the other students to ask the student questions about that area. When a wrong answer is given, swap to a different

student.

Ask students to respond to this ‘Agony Aunt’ letter from a plant.

Dear Aunty Agapanthus, I am an extremely rare species of orchid. I just can’t decide if I should clone myself by growing a cutting, or if it would be better off using a tissue culture of my meristem cells. What do you think? Please also tell me why you think this, as I want to explain to my friends.

Look for answers that explain that growing cuttings can be a disadvantage if the parent plant has a disease,

because the offspring is likely to contract the disease too. Tissue culture using meristem cells will give the

opportunity to get rid of the disease as it will not be found in the meristem cells. Also there is less chance of

genetic variability.

After the cloned plants have grown for a few days, ask students to observe them. They will find that the plants look

identical in terms of leaf shape and colour, but may have different sizes. Ask the students to explain why this is,

using ideas about genetic and environmental variation.

Student Book answers Q1 By putting the cut end of a shoot into water or moist earth.

Q2 A powder that helps the growth of roots from shoots.

Q3 Tissue culture saves time and money and you can grow plants out of season.

Q4 Each cell grows into a new plant.

Q5 The plants produced will be exact copies of their parent.

Q6 Various – could include palisade cells, phloem cells, and root hair cells.

Practical sheet answers Q1 Asexual – no need for two parents

Q2 Same colour – genetically identical

Q3 No - variations in environment.

Q4 No – not possible due to lack of totipotency in animal cells.



b5_04 Plant clones

P Taking cuttings

Objectives

In this activity you will:

� prepare a cutting from a healthy geranium plant.

Be careful when cutting the plant.

Wash your hands after handling compost.

Equipment and materials

small plastic pot and dish • warm water • compost • sharp knife or scissors •

fully grown and healthy geranium plant • labels • permanent marker • clear plastic bag

Method

1 Fill the plant pot with compost. Press it down lightly to make it firm.

2 Stand the pot in the dish. Fill the dish with warm water.

3 Let the soil soak up the water for 30 minutes.

4 Remove the water from the dish. Let the compost pot drain in the empty dish while you carry out the next step.

5 Cut the stem of the plant just below a leaf using the knife or scissors.

6 Leave just the top two to three leaves. Remove all the other leaves from the stem.

7 Gently insert the cutting into the compost up to its lowest leaf.

8 Label the pot with the date of the cutting.

9 Remove any excess water from the dish and place the pot in the dish. Cover it with the clear plastic bag, making sure the bag doesn’t touch the cutting.

10 Leave to settle for a few days in the shade. Then place the cutting in a light place but out of direct sunshine. Water it only if the surface of the compost feels dry.

11 The cutting should begin to take root in about 15–20 days. If it looks healthy and is beginning to take up water more quickly, it has probably rooted.

Results

Draw the plant roots you can see after 20 days.

Questions

1 Is this an example of sexual or asexual reproduction? Explain your answer.

2 Will any flowers on the new plant be the same colour as those on the parent plant, or could they be different? Explain your answer.

3 Will the new plant grow to be exactly the same size as the parent plant? Explain your answer.

4 Could this technique be used to clone you? Explain your answer.



b5_04 Plant clones

Technician sheet


� fully grown and healthy geranium plant

For each group:

� small plastic pot and dish

� warm water

� compost

� sharp knife or scissors

� label

� permanent marker

� clear plastic bag

Method

See practical sheet b5_04.

Notes

� The potted cuttings will need to be put in the shade to settle for a few days. After this, a light place out of direct sunlight is needed.

� Water cuttings only if the surface of the compost feels dry.

� Warn students about safe use of the knife.

� Count in and out all knives.



b5_05 Plant development

Resources

Student Book pages 50–51 � Interactive Book: Quick starter ‘Plant hormones’; Drag and drop ‘Phototropism’ � Homework pack b5_05

Files on Teacher Pack CD: b5_05_worksheet, b5_05_practical; b5_05_technician

Equipment for practical

Learning outcomes B5.1.12 understand that the growth and development of plants is also affected by the environment, e.g.

phototropism

B5.1.13 understand how phototropism increases the plant’s chance of survival

B5.1.14 explain phototropism in terms of the effect of light on the distribution of auxin in a shoot tip

Ideas about Science IaS 3.1 scientific hypotheses, explanations and theories are not simply summaries of the available data. They are

based on data but are distinct from them

IaS 3.2 an explanation cannot simply be deduced from data, but has to be thought up creatively to account for the

data

IaS 3.3 a scientific explanation should account for most (ideally all) of the data already known. It may explain a

range of phenomena not previously thought to be linked. It should also enable predictions to be made about new

situations or examples

IaS 3.4 scientific explanations are tested by comparing predictions based on them with data from observations or

experiments

Literacy focus: Creating sentences when given different combinations of key words.

ICT focus: Using animations about plant tropisms.


� understand how growth and development of plants is affected by the environment

� understand how phototropism increases the plant’s chance of survival

Key vocabulary

photosynthesise �� phototropism �� positively phototropic �� auxin (Higher tier)


� Show some pictures of plants in a dim room growing towards a source of light, such as Figure 1 on p. 50 in the

Student Book. Ask students about this phenomenon and brainstorm what would happen if the plant was turned

round towards the dark. Students should be able to understand that the plant would grow towards the light again,

and that this would continue if the plant was turned round once more. Ask how the plant knows which way to turn

if it doesn’t have eyes.

Learning activities worksheet b5_05 + practical b5_05 Low demand � Make up several sets of cards to use for the learning activities in this lesson. The cards should

have the following words on them: carbon dioxide, water, oxygen, glucose. Tape a card under each of the stools in

the classroom before the students enter. Students have to reach under the seat when they are asked to, read the

word and stand in the correct group. Several in the class will have the same words so they need to find a group

that is missing their word. Once they are in groups, they need to rearrange themselves to represent the

photosynthesis equation. Ask what other conditions are needed (light, chlorophyll).

Standard demand � Put students in pairs and ask them to arrange the word cards to make the photosynthesis

equation. Ask them to think in their pairs about what would happen to a plant if the amount of available light was

reduced. Elicit the idea that light is needed for chlorophyll development in a plant. Without chlorophyll, there would

be no photosynthesis.

Introduce the term ‘phototropism’ and its meaning, making sure that the students use the idea of plants growing

towards light rather than bending towards it. Students can then carry out the practical activity detailed on practical

sheet b5_05.

b5_05 Plant development continued


Teaching and learning notes: All the activities on the worksheets allow students to both recap their prior

knowledge and build on it. The teacher should decide if it is appropriate for the class to handle scissors in the

practical. Students should do a risk assessment before the practical, and you should check their plans before they

start work.

High demand � Higher tier students need to be able to use the term ‘auxin’ when describing the growth of a shoot

towards light. Explain how auxin is concentrated in the shady part of a plant. Also get students to draw elongated

cells next to short cells so that they understand why a shoot bends. Use images from the internet about Darwin’s

experiments with shoot tips to show the relation between auxin and growth.

The third worksheet activity requires students to use Ideas about Science in explanations. They are guided through

the early experiments involved in the discovery of the role of auxin in phototropism. They need to suggest which

explanations best explain the data and justify their decisions.

Plenary suggestions Ask students to summarise what they have learned in the lesson, in exactly ten words.

Student Book answers Q1 Light, water and carbon dioxide

Q2 Photosynthesis produces food for the plant. Without photosynthesis a plant would not grow.

Q3 Grows towards the light

Q4 The leaves are in the best situation for photosynthesis.

Q5 In the shaded part of the plant

Q6 Auxin makes the shoot grow longer on the shaded side and this makes the shoot curve towards the light.

Practical sheet answers Q1 So that they receive maximum light

Q2 Plant hormones such as auxin, which is produced on the shaded side of a shoot

Q3 Yes, the roots will still grow downwards and the shoots will still grow upwards. Roots grow towards gravity and

shoots grow towards light.

Q4 No, it is not a growth response


Drawing on the left should show a plant growing towards the light. Drawing on the right should show a plant

growing straight up.


Q1 A plant that can grow towards the light has a better chance of being able to photosynthesise and produce food.

It therefore has a survival advantage over a plant that is unable to photosynthesise because its leaves are in

the shade.

Q2 a) Diagrams should show the shoot growing towards the light and the root growing away from the light.

Students may also show the auxin in the shaded parts.

b) Diagrams should show the root growing downwards and the shoot growing upwards.


Q1 A

Q2 B

Q3 C

Check student justifications for each of the above.




P Phototropism in plants

Objectives


� find out what plants do if they are not in the light.

Be careful with scissors.

Do not eat the cress or seeds.


black paper • scissors • adhesive tape • cress seeds • permanent marker •

plastic Petri dish with cover • filter paper

Method

1 Fit the filter paper into the bottom of the Petri dish and wet it sparingly with water.

2 Add around 30 cress seeds to the Petri dish.

3 Cover the top of the Petri dish with black paper that has a shape cut in it to let light in.

4 Cover the sides of the Petri dish with black paper and tape it down to prevent light getting in.

5 Write your name and date on the bottom of the Petri dish and leave it in a cool, light place to allow the seeds to grow for a few days.

Results

Draw what you see in the Petri dish and write a sentence or two to summarise what has happened.

Questions

1 Why do plants grow towards light?

2 Plants don’t have eyes. How do they know which way to grow?

3 What happens if you plant a seed upside down? Do plants know which way is up?

4 Is the movement of a sunflower an example of phototropism? Explain your answer.




Technician sheet


� cress seeds

� black paper

� scissors

� adhesive tape

� permanent marker

� plastic Petri dish with cover

� filter paper

Method


Notes

� The Petri dishes should be placed in a light and cool place out of direct sunlight.

� There is no need to water the dishes.




1 How light affects plants

Draw a plant in each pot to show how it is affected by the light.

2 Phototropism

1 Explain how phototropism may give a plant a survival advantage over another plant that is not phototropic.

2 a) Draw diagrams of a root and a shoot with light falling on them from one direction. Show which way they will each grow.

b) Now draw the direction of growth of the root and the shoot of a seed placed sideways in the soil.

3 Do some research on the internet to find out what other tropisms affect plant growth.

3 Developing explanations

1 Darwin carried out the experiment shown below. He covered the tips of shoots and found that they didn’t bend in the light. He covered the stems and found that the shoots did bend. Which of the explanations below best explains these results? Explain your answer.

A The tip of the stem is the most photosensitive.

B The middle of the stem is the most photosensitive.

C The bottom of the stem is the most photosensitive.

b5_05 Plant development continued


2 Boysen-Jensen carried out the experiment shown below. He inserted mica into shoots, and they then failed to bend in the light. Below are some explanations for these results. Choose the best explanation and explain your choice.

A An ‘influence’ causes the bending and is produced on the lit side of the shoot.

B An ‘influence’ causes the bending and is produced on the shaded side of the shoot.

C An ‘influence’ causes the bending and is produced on both sides of the shoot.

3 F.W. Went put tips of shoots on agar blocks and put the blocks on other shoots with their tips cut off, as shown in the diagram. He found that the shoots bent away from the side with the agar block and concluded that shoot tips contain a chemical that diffuses into the agar blocks. It was found that this chemical affects the growth of cells, and it was named auxin. Later studies found that auxin also made roots grow away from light.

There were many different explanations offered for how auxin caused plant shoots to grow towards light. Choose the best explanation from the options below, and explain why you think it is the best.

A Light inactivates the auxin on the lit side, which then grows faster than the shaded side.

B Auxin encourages uptake of mineral nutrients such as nitrogen.

C Auxin makes the plant’s cells elongate on the shaded side, bending the shoot towards the light.



b5_06 Mitosis

Resources

Student Book pages 52–53 � Interactive Book: Naked Scientist animation ‘How are new cells formed?’ � Homework pack b5_06


Black and white plastic knives, forks and spoons; wool or string of two different colours; animation of mitosis

Learning outcomes B5.2.1 recall that cell division by mitosis produces two new cells that are genetically identical to each other and to

the parent cell

B5.2.2 describe the main processes of the cell cycle: a) cell growth during which numbers of organelles increase

and the chromosomes are copied when the two strands of each DNA molecule separate and new strands form

alongside them; b) mitosis during which copies of the chromosomes separate and the nucleus divides

Numeracy focus: Carrying out calculations of chromosome numbers.

ICT focus: Using animations about mitosis.


� recall that cell division by mitosis produces two new cells that are genetically identical

� describe the cell cycle

Key vocabulary

mitosis �� daughter cells


� Play ‘stand up − sit down’: ask students to make a list of all the important words they have learned so far about

genetics. Then ask the whole class to stand and ask one individual to read their list out. All the other members of

the class cross the word off their list as it is read out, and sit down once all their words are crossed off. Then

continue with other students’ lists and do the same. Very soon there will only be a few standing – these are the

ones with the most detailed and comprehensive lists. The ‘winner’ is the student with the most (acceptable)

words on their list.

Learning activities worksheet b5_06

Low demand �� Use an animation to show how mitosis results in two genetically identical daughter cells.

Demonstrate mitosis by using one white and one black knife, fork and spoon to represent a pair of chromosomes.

One coloured strand of wool is the nuclear membrane and the other is the cell membrane. Demonstrate the

copying of chromosomes by adding more knives and forks, and the removal of the nuclear membrane by removing

the wool. Line up the cutlery in the centre and show how one of each pair goes to each end of the cell. Pinch the

cell membrane to make two cells and reform the nuclear membrane in each cell. You can add other parts to the

model to suit the ability of the students. Get students to make their own models with one person as the ‘explainer’.

Students can do activity 1 on the worksheet. Check their sentences.

Standard demand �� Students can use the Student Book p. 52 or other resources to draw the series of steps in

mitosis. Ensure they can put the statements in question 1 of worksheet activity 2 in the correct sequence.

Encourage them to consider the fate of the daughter cells once cell division has occurred, i.e. they may undergo

differentiation or go on to divide again.

Teaching and learning notes: This lesson aims to explain to students how a cell divides in mitosis. It is important

that students understand the chromosome numbers involved at each step; remind them of these so that they are

not confused.

High demand �� The modelling activity can be expanded to include elastic bands denoting centromeres, more wool

for spindle fibres, and beads for centrioles. The students can find out what these parts are and how they help in the

process of mitosis.

b5_06 Mitosis continued


Plenary suggestions Students could each write a true/false statement about mitosis and then read them out in turn. The rest of the class

listen to the statements and vote on whether they think the statement is true or false by standing up for true

statements and sitting down for false statements. You will quickly see if there are any misconceptions or areas that

need to be further addressed.

Student Book answers Q1 Mitosis is a kind of cell division that takes place in normal body cells.

Q2 46

Q3 Daughter cells would have fewer chromosomes than the original cells.

Q4 Students’ own diagrams – should be similar to the diagram at the bottom of p. 52 in the Student Book but with

just one pair of chromosomes rather than two.

Q5 92

Q6 46


Q1 True

Q2 False – In mitosis, a cell divides into two daughter cells.

Q3 False – The daughter cells are identical to the parent cell.

Q4 False – There are 46 chromosomes in a human liver cell.

Q5 True

Q6 False – New cells are the same as the old cells that they replace.


Q1 A, F (these first two stages can be either way around), C, D, E, B

Q2 a) i) 46 ii) 46

b) During growth and replacement of old or damaged cells

c) So that there are the same number in the daughter cells


Q1 The first stage of the cell cycle is cell growth. The cell grows, makes copies of its chromosomes and increases

the number of organelles in the cell. The second stage is mitosis, when the copied chromosomes divide into

two new nuclei and then the whole cell splits to give two new daughter cells.

Q2 The number of organelles increases so that each daughter cell has enough of these to function properly. Some

organelles also have an important part to play in cell division.

Q3 The Hayflick limit is the number of times a cell may undergo mitosis – usually around 50 times in human cells.



b5_06 Mitosis

1 Mitosis

Read the following sentences about mitosis and decide which ones are true and which ones are false. Rewrite any false ones to make them true.

1 Mitosis is a kind of cell division that takes place when an animal grows. True/False

............................................................................................................................................

2 In mitosis, a cell divides into four daughter cells. True/False

............................................................................................................................................

3 The daughter cells are not identical to the parent cell. True/False

............................................................................................................................................

4 There are 45 chromosomes in a human liver cell. True/False

............................................................................................................................................

5 Some cells in your body do not live as long as you do. True/False

............................................................................................................................................

6 New cells can be different from the old cells that they replace. True/False

............................................................................................................................................

2 Stages in mitosis

1 Put these steps of the cell cycle in the correct order.

A Each chromosome in the nucleus makes an identical copy of itself.

D The chromosomes and their copies move to the centre of the cell.

B The cytoplasm divides and nuclear membranes form to give two new identical cells.

E The two copies of each chromosome separate and move to opposite ends of the cell.

C The nuclear membrane breaks down. F The number of organelles in the cell increases.

............................................................................................................................................

b5_06 Mitosis continued


2 The diagram below shows the stages of mitosis:

a) Give the number of chromosomes present in:

i) Cell A ii) Cell B

b) When does this type of cell division take place?

c) Why must a cell make a copy of its chromosomes before dividing?

3 The cell cycle

1 Explain what the cycle of events is in the cell cycle.

2 Why does the number of organelles increase before the cell divides?

3 Find out about the Hayflick limit and explain its relationship to mitosis.



b5_07 Meiosis

Resources

Student Book pages 54–55 � Homework pack b5_07


Pipe cleaners, sugar paper and felt-tip pens; beads in two dishes

Learning outcomes B5.2.3 recall that meiosis is a type of cell division that produces gametes

B5.2.4 understand why, in meiosis, it is important that the cells produced only contain half the chromosome

number of the parent cell

B5.2.5 understand that a zygote contains a set of chromosomes from each parent

Numeracy focus: Calculating chromosome numbers.


� recall that meiosis is a type of cell division that produces gametes

� understand why it is important that cells produced by meiosis contain only half the chromosomes

� understand that a zygote contains a set of chromosomes from each parent

Key vocabulary

meiosis �� gametes


Students may struggle with the difference between mitosis and meiosis. They may have particular difficulty with the

idea that in mitosis the parent cell undergoes one cell division, whereas in meiosis the parent cell undergoes two

cell divisions.


� Key word draw: have five cards with the following key words on them: clone, chromosome, stem cell, mitosis,

specialised cell. Divide the class into two teams. Each team nominates someone to come up and draw a picture

that represents the key word on the whiteboard. The team that calls out the correct word first gets a point. The

winning team is the one with the most points after all five words.

� Explain to the class that in this lesson they are going to learn about a different type of cell division, in which the

cells produced have only half the chromosome number of the parent cell.

Learning activities worksheet b5_07 Low demand � Introduce students to the second type of cell division, meiosis, in which gametes are produced. It is

important to make sure that they are familiar with the key vocabulary for both mitosis and meiosis and are confident

in its use. Students should do activity 1 on the worksheet.

Model meiosis for the students using sugar paper with cells drawn on and pipe cleaners to represent the

chromosomes. Show the duplication of the chromosomes and the first meiotic division followed by the second

meiotic division. Clear any misconceptions as they arise.

Standard demand � Explain why the gamete number is halved by using beads (initially 46 in each of two dishes).

Explain that one dish is the egg cell and the other is the sperm cell. Add the contents of the ‘sperm’ dish to the ‘egg’

dish and ask students how many chromosomes there would be in the cell resulting from this fertilisation. Elicit the

idea that all the cells in the resultant embryo will have more than 46 chromosomes. Discuss the possible

implications of this. Then ask students to do the worksheet to consolidate these ideas.

Teaching and learning notes: Make sure that students are able to explain why chromosome numbers in gametes

are halved using the activity above.

High demand � In groups of no more than four, students debate or discuss the questions in activity 3 on the

worksheet. If time allows, they could find out if there are any organisms with an odd number of chromosomes and

why this happens (different species interbreeding) and what the outcome is in terms of gametes (infertility).

Examples could be mules, ligers, zebroids. Feedback could be taken in the form of questioning or writing a report

for homework if there isn’t enough class time.

b5_07 Meiosis continued


Plenary suggestions Revisit the ‘students are learning to’ objectives of the lesson. Ask the students to share, on a scale of 1–10, how

confident they are that they have met each objective and why they have made that judgement. Check their

calibration by asking suitable open questions.

Student Book answers Q1 Ovaries

Q2 They have only 23 chromosomes (or they are the sex cells).

Q3 92

Q4 They have only 23 chromosomes while the parent has 46 chromosomes (also they differ genetically).

Q5 In the pollen grains (anthers) and in the ovules (ovary)

Q6 The number of chromosomes is reduced, for example from 46 to 23 in the human.


Meiosis, four, sex cells, sperm, ova, half


Q1 a) C

b) 23

c) Twice

d) So that there will be the correct number of chromosomes after fertilisation.

Q2 The remaining two cells should contain:

i) a long black chromosome and a short white one

ii) two white chromosomes (one long and one short).


Q1 a) So that all the gametes can have an equal number of chromosomes.

b) The way the chromosomes split up into the different gametes is random – the mother’s chromosome may go

into any gamete, as may the father’s chromosome.

Q2 a) 64

b) 16 – the pattern is 2x where x is the number of chromosomes.

Q3 There are a possible 223 combinations of chromosomes in a gamete from a human cell.



b5_07 Meiosis

1 Meiosis

Fill in the blanks using the words from the box. Note: not all of these words will be used.

half double mitosis meiosis two four three ova sperm sex cells

The type of cell division that takes place in the testes of a male and the ovaries of a female

is called ......................... This results in the formation of ........................... gametes.

Another name for gametes is ............................ The gametes of a male are called

.......................... and the gametes of a female are called ........................ Gametes

are different to parent cells as they contain ....................... the number of chromosomes.

2 The stages of meiosis

1 The diagram below shows the stages of meiosis:

a) Which letter denotes the gametes?

b) Give the number of chromosomes present in cells C.

c) How many times does the parent cell divide in meiosis?

d) Why is it important that gametes have only half the number of chromosomes as the parent cell?

b5_07 Meiosis continued


2 The diagram below shows cells from an organism that has only two pairs of chromosomes in each cell. There are four different gametes that could be formed. The diagram shows two of these combinations. Complete the diagram by drawing the chromosomes in the empty gametes to show the different combinations of chromosomes they could have.

3 The importance of meiosis

1 Use what you know about meiosis to explain:

a) why the total number of chromosomes in almost every species is an even number

b) why brothers and sisters from the same parents are not exactly alike.

2 A mosquito has six chromosomes in its nucleus.

a) Work out how many different combinations of chromosomes its gametes may have. Compare this with the answer for two chromosomes in activity 2 above.

b) Now work out the number of different combinations if there are four chromosomes. Is there a pattern? How could this pattern be represented mathematically?

3 Use your answer to question 2b) to work out how many combinations of chromosomes are possible in a human gamete.



b5_08 Chromosomes, genes and DNA

Resources

Student Book pages 56−57 � Interactive Book: Quick starter ‘The genetic code’ � Homework pack b5_08

Files on Teacher Pack CD: b5_08_worksheet; b5_08_practical; b5_08_technician

Pipe cleaners, modelling clay; animation of cell, nucleus, chromosomes, genes and DNA; 3D model of DNA; DNA modelling kit

Equipment for practical

Learning outcomes B5.3.1 recall that DNA has a double helix structure

B5.3.2 recall that both strands of the DNA molecule are made up of four different bases which always pair up in

the same way: A with T, and C with G

B5.3.3 understand that the order of bases in a gene is the genetic code for the production of a protein

Literacy focus: Composing sentences; developing arguments in a group.

Numeracy focus: Looking at patterns and interpreting graphs.

ICT focus: Using an animation of the cell, chromosomes and DNA.


� recall that DNA has a double helix structure

� recall that both strands of the DNA molecule are made up of four different bases that always pair up in the same

way: A with T, and C with G

� understand that the order of bases in a gene is the genetic code

Key vocabulary

chromosomes �� DNA �� double helix �� bases �� nucleotide

base pair �� genes �� genetic code


You may need to mention again the different ways in which chromosomes are drawn. Books often draw

chromosomes in the ‘X’ shape. However, when cells are not dividing, chromosomes look like a single cylinder –

this is what the chromosome looks like before replication.


� Do a quick review of what students have already learned in this topic, as well as a recap from module B1. They

need to recall what genes are and why they are important. A good way of getting the students to do this is to

write a list of the key vocabulary (gene, protein, code, DNA, chromosome, nucleus) on the board and ask them

either to explain to a partner what they know about each of the terms, or to write a paragraph using all the key

words.

Learning activities worksheet b5_08 + practical b5_08 Low demand � Show students an animation of the cell, nucleus, chromosomes, genes and DNA. Show a 3D

model of DNA.

Use the card-sort activity in activity 1 of the worksheet to elicit students’ understanding of the topic. Make sure that

the key words on the cards are understood by all students. Repeat this activity if necessary.

Write these words on the board: cell, nucleus, chromosome, gene. Ask students to place them in order of size.

Teaching and learning notes: You can repeat this last activity several times – the practice is important.

Standard demand � Ask pairs of students to use pipe cleaners or modelling clay to model the relationship between

DNA, genes, chromosomes and proteins. Then ask each pair to share their outcome with another pair and to give

each other feedback. Share the feedback with the class. This is a good opportunity to show students the difference

between un-replicated and replicated chromosomes, in order to avoid misconceptions.

Students can make their own models of DNA using kits (available from the Science Museum catalogue).

Demonstrate or set up a class practical to extract DNA from bananas – see the practical sheet and technician

sheet for details. As an extension, other fruits or vegetables could be tried, such as peas, onion, kiwi, apple.

b5_08 Chromosomes, genes and DNA continued


Teaching and learning notes: Make sure that students understand that chromosomes are not X-shaped until they

have been replicated.

You will need to decide if it is appropriate for your class to carry out the whole practical. You may decide to

prepare some of the steps in advance such as mashing up the fruit.

High demand � Students discuss the question ‘Genes, chromosomes and DNA – are these just different names for

the same thing?’ the ideas to be elicited are that DNA is a chemical that winds up into a double helix and is

wrapped densely (around proteins) to form chromosomes. Genes are sections of DNA that code for a particular

protein. Make sure they justify their answers.

Plenary suggestions Students could each write a true/false statement about genes and chromosomes and then read them out in turn.

The rest of the class listen to the statements and ‘vote’ on whether they think each statement is true or false by

standing up for true statements and sitting down for false statements. You will quickly see if there are any

misconceptions or areas that need to be further addressed.

Student Book answers Q1 Chromosomes look like long, threadlike structures and are found in pairs.

Q2 Inside the nucleus – makes up the chromosomes (do not accept in chromosomes).

Q3 Students’ own diagrams – should show one phosphate, one sugar and one base, similar to a single unit of the

diagram at the bottom of p. 56 in the Student Book.

Q4 Two strands (of DNA) twisted together (like a spiral staircase)

Q5 No, genes are made of sections of DNA. DNA units consist of a sugar, a phosphate and a base. A gene codes

for a protein.

Q6 The sequence of bases on DNA that codes for a protein is called the genetic code.


DNA – bottom diagram – has a double helix structure.

Chromosomes – second diagram from top – made of DNA molecules; there are 46 of these in human cells.

Gene – third diagram from top – has instructions for making proteins; section of a DNA molecule.

Nucleus – top diagram – part of the cell that contains chromosomes.


Q1 a) Double helix b) DNA c) Nucleus

d) Gene e) Bases f) Sugar/phosphate

g) Chromosomes

Q2 a) 38

b) Horse

c) They are all even numbers.

d) No – the smallest organism (mosquito) does have the least chromosomes, but several other organisms don’t

fit the pattern, e.g. a shrimp has more chromosomes than a horse.

Practical Sheet answers Q1 Several factors affect the amount of DNA extracted from a fruit sample. Some of these have to do with actual

amount of DNA in the fruit cells, such as the:

• number and size of chromosomes • ploidy of the plant’s cells (how many copies of each chromosome)

Other factors are due to variation on the number and characteristics of the fruit cells, including:

• the number of cells in the fruit sample • characteristics of the fruit (such as thickness and composition of

the cell walls) that affect how well the extraction procedure worked.

Variation in the DNA extraction can also have an important effect. These variations include:

• how thoroughly the fruit was mashed • how much liquid was saved from filtering the mashed fruit

• the temperature of the fruit mixture during the procedure • the time that the procedure took.

The amount of DNA extracted from each fruit may correlate with the number of chromosomes in each cell, but

other factors may have a greater effect.




P Extracting DNA

Objectives


� extract DNA from bananas.

Wear eye protection.


two 250 cm3 beakers • 500 cm

3 beaker • balance • salt • ice-cold ethanol • filter paper • funnel •

banana pieces • 25 cm3 measuring cylinder • 250 cm

3 measuring cylinder •

pestle and mortar stirring rod • washing-up liquid • hot water • wire hook

Method

1 Put 100 cm3 of water in a 250 cm3 beaker and dissolve 3 g of salt in it.

2 Add 10 cm3 of washing-up liquid and stir until it dissolves.

3 Break up the pieces of banana well using the pestle and mortar. Put these mashed-up pieces in another 250 cm3 beaker.

4 Add an equal volume of the washing-up liquid and salt solution you made earlier.

5 Put the beaker in a larger beaker of hot water and leave for 15 minutes.

6 Filter the mixture and collect the juice in a small beaker. Leave it to cool.

7 Tilt the beaker and pour ice-cold ethanol down the side of the beaker very slowly and carefully. Stop when you have as much ethanol as juice.

8 You should see a white layer forming between the juice and the ethanol. Let it clump together and then lift some out using a wire hook.

Results

Describe the appearance of the DNA you extracted.

Summarise the main steps involved in extracting DNA from bananas.

Question

1 Do you think your results would have been different if you had used fruit or vegetables other than bananas? Explain your answer.




Technician sheet


� bananas

� peas, onions, kiwis, apples (as an extension)

For each group:

� two 250 cm3 beakers

� 500 cm3 beaker

� balance

� salt

� ice-cold ethanol

� filter paper

� funnel

� 25 cm3 measuring cylinder

� 250 cm3 measuring cylinder

� pestle and mortar

� stirring rod

� washing-up liquid

� hot water

� wire hook

Method


Notes

� The banana pieces could be mashed up before the practical, removing the need to provide each group with a pestle and mortar.

� The ethanol should be ice-cold and kept in the freezer until step 7 (see the method on the practical sheet).




1 Chromosomes and DNA

Cut out the cards below and sort them into groups. Each group should contain the name of a substance or structure important in this topic, a diagram of it, and at least one fact about it.

made of DNA molecules

has instructions for making proteins

DNA

chromosomes

gene

part of the cell that contains chromosomes

nucleus

there are 46 of these in human cells

section of a DNA molecule

has a double helix structure

b5_08 Chromosomes, genes and DNA continued


2 Structure of DNA

1 Write the correct words in the box next to the meanings in the table.

Word Meaning

a) the two strands of DNA twisted together

b) the long molecules that make up genes and chromosomes

c) the part of the cell that contains chromosomes

d) a section of DNA that codes for a protein

e) chemicals that hold the two strands of DNA together

f) a chemical that makes up the backbone of the DNA molecule

g) very long DNA molecules that are found in pairs in the nucleus

2 Look at the bar chart below.

a) How many chromosomes does a body cell in a cat have?

b) Which species has 64 chromosomes in its cells?

c) What do all the chromosome numbers of these species have in common?

d) Do you think there is a relationship between the number of chromosomes in the cells and the size of the organism? Explain your answer.

3 Genes and base pairs

Explain how the order of bases in a gene codes for a particular protein. Use diagrams in your explanation.



b5_09 Making proteins

Resources

Student Book pages 58–59 � Homework pack b5_09


Paper and modelling clay; animation of protein synthesis

Learning outcomes B5.3.4 explain how the order of bases in a gene is the code for building up amino acids in the correct

order to make a particular protein

B5.3.5 recall that the genetic code is in the cell nucleus of animal and plant cells but proteins are produced in the

cell cytoplasm

B5.3.6 understand that genes do not leave the nucleus but a copy of the gene (messenger RNA) is produced to

carry the genetic code to the cytoplasm

ICT focus: Accessing the internet for research into protein synthesis.


� recall that the genetic code is in the cell nucleus

� understand that proteins are produced in the cell cytoplasm

� understand that genes do not leave the nucleus

Key vocabulary

cytoplasm �� membrane �� nucleus �� chromosomes �� ribosomes

amino acids (Higher tier) �� messenger RNA (Higher tier)


It is necessary that students understand why proteins are important in the cell. They need to understand that all

functions and characteristics of the cell are due to proteins.


� Prior to the lesson, make some cards with key words such as chromosome, nucleus, DNA, gene written on them.

Stick cards under four of the stools. At the start of the lesson ask the students to check under their seats. The

students with the cards come to the front and stand in order of smallest to largest (according to key word). The

rest of the class can ask them questions about their key word. The students at the front are allowed to confer in

order to answer.

Learning activities worksheet b5_09 Low demand � Elicit ideas about variation and why people look different. Relate this to the proteins that are made

in each cell and some of the jobs that they do. Discuss the parts of the cell and the role each part plays in protein

production. Use Activity 1 on the worksheet to make up cards that can be sorted into the correct sentences. Make

sure the students understand the role of DNA as providing the code for protein synthesis. Use a role-play example

of a sweet factory owner who writes recipes for different sweets in her office (the nucleus) which are then taken to

the factory (the ribosome) to be read and made into sweets.

Teaching and learning notes: Many animations on the internet of protein synthesis are too complex and will

cause confusion to low-attaining (and other ) students. A suitable way to visualise the concepts is to make a model

using paper and modelling clay (there are many suitable models to refer to available on the internet). An effective

model would be one in which the student understands that copying of the DNA occurs in the nucleus and that the

copied message leaves the nucleus to be read by the ribosome outside.

Standard demand � Students use their notes and the Student Book to research the answers to the questions in

activity 2 on the worksheet. Afterwards ask students to come back together to share their findings. Then ask them

to write (individually) a couple of sentences to explain protein synthesis. Students could work in groups to write a

script and ‘perform’ protein synthesis. Make a list of important points from the learning outcomes as criteria for peer

assessment. It would be useful to have some information (carefully selected by the teacher) from the internet

available for them to use, as well as the Student Book. Ask questions from real-life situations: Why does the dentist

cover individuals with a lead apron when taking X-rays? Why does the X-ray technician stand behind a lead wall?

Why should people use sun screen? Why should you avoid tanning beds? All of these help to protect people from

radiation so that their DNA is not mutated. Elicit why it is important that DNA is not mutated.

b5_09 Making proteins continued


Teaching and learning notes: Research on the internet works best if it is focused on a few important questions

and a few suitable websites such as BBC bitesize, University of Utah genetics and Science Aid. Key questions are:

What is the difference between DNA chromosomes and genes?

What does DNA look like?

Where is DNA found?What are DNA bases?

Why are DNA bases important?

What is the genetic code?

How does the genetic code affect the production of a particular protein?

High demand � Higher tier students need to know more detail of protein synthesis – the role of messenger RNA,

and how amino acids are built up to form different proteins. Refer to the Higher section of the Student Book, p. 59.

As an extension, introduce students to new vocabulary such as codons, tRNA, transcription and translation (these

are not specification requirements). Ask them to find out what these words mean and how they are related to

protein synthesis. Observe students and note their conversations to determine their level of understanding. You

could show a carefully chosen animation of protein synthesis if you think students will benefit from this. Use the

card-sort in activity 3 on the worksheet to assess learning.

Plenary suggestions Students make a glossary of terms to remind them of how proteins are made.

Student Book answers Q1 In the nucleus of a cell

Q2 Proteins are made (or chemical reactions occur)

Q3 Small structures in the cytoplasm that make proteins

Q4 In the cytoplasm

Q5 The proteins that are produced in it and make up its structure, which is in turn determined by the genetic code.

Q6 No, proteins have a specific shape and function dependent upon the particular sequence of amino acids. The

sugars in milk will have a different structure to those in fruit, so they will need a particular protein with a

particular matching structure to digest them.


Q1 Nucleus – contains genetic information

Cell membrane – controls the movement of substances

Cytoplasm – where proteins are made

Chromosome – carries instructions to make protein

Q2 a) Cell membrane b) Cytoplasm

c) Nucleus d) Chromosome


Q1 a) 2 b) 4 c) Pairs d) Double helix

Q2 The order is: DNA unzips; mRNA copies the DNA; mRNA leaves the nucleus; mRNA moves to the ribosome;

the ribosome produces a chain of proteins.


Q2 a) G, D, A, H, B, E, C, F

b)The first two (G and D) are transcription and the rest are translation.



b5_09 Making proteins

1 Proteins

1 Draw lines to match the parts of the cell to their descriptions.

nucleus where proteins are made

cell membrane contains genetic information

cytoplasm carries instructions to make proteins

chromosome controls the movement of substances

2 Use the list of cell parts in question 1 to label the diagram below.

2 Getting the message across

1 Below are some features of DNA. Draw a ring around the correct answer in each row.

a) number of strands 1 2 3 4

b) number of different bases 2 3 4 5

c) arrangement of bases between the strands

single pairs triplets fours

d) shape of the molecule circular cubic double helix

zig-zag

b5_09 Making proteins continued


2 Arrange the following statements, about how proteins are made, in the correct order. Draw a flow chart.

Messenger molecule moves to the ribosome

The ribosome produces a chain of proteins

Messenger molecule copies the DNA

Messenger molecule leaves the nucleus

DNA unzips

3 The genetic code

1 There are millions of different proteins made by cells, but there are only 22 different amino acids. Explain how this is possible. Share your ideas with a partner and decide which is the best explanation.

Extension

2 Find out about the processes of transcription and translation in protein synthesis.

a) Put the stages below in the correct order.

b) Which are part of transcription and which are part of translation?

A mRNA leaves through nuclear pores

B tRNA matches codon

C Stop codon is read

D mRNA is made

E Peptide bonds are formed

F mRNA and protein are released

G DNA is unzipped

H mRNA attaches at ribosome

3 Find out what the one gene–one protein theory is and write a paragraph explaining what it means.

4 The genetic code is said to be ‘universal’. Find out what this means and explain it in your own words.



b5_10 Cell specialisation and gene activity

Resources

Student Book pages 60–61 � Interactive Book: News clip ‘Cells, tissues and organs’ � Homework pack b5_10


Learning outcomes B5.3.7 understand that although all body cells in an organism contain the same genes, many genes in a particular

cell are not active (switched off) because the cell only produces the specific proteins it needs

B5.3.8 understand that in specialised cells only the genes needed for the cell can be switched on, but in

embryonic stem cells any gene can be switched on during development to produce any type of specialised cell

B5.3.9 understand that adult stem cells and embryonic stem cells have the potential to produce cells needed to

replace damaged tissues


� understand that many genes in a particular body cell are not active

� understand that in stem cells genes can be switched on

� understand that stem cells have the potential to produce cells needed to replace damaged tissues

� discuss the ethical arguments around the use of embryonic stem cells

Key vocabulary

switched off (genes) �� switched on (genes) �� active (genes) �� stem cell therapy


There are different types of stem cells and students may be confused by the use of the same term ‘stem cell’ to

describe these different types. It is important that students understand the difference between the two types of

human stem cell and understand how both are different from plant stem cells (meristem cells).

It is difficult for lower attaining students to understand that the same genes are found in all body cells. They may

find it hard to grasp the idea that some genes are turned off when a cell becomes specialised. An analogy with a

sports shop may help – there are many types of sporting goods available but a shop specialising in football will only

want to display football-related products. The other goods available will be ‘switched off’. Make sure they don’t form

the misconception that these other goods are removed (implying that switched-off genes are removed).


� Show a light switch and get the students to think about how a light switch controls light by asking questions such

as ‘how can I light a room?’ how do I make the room dark?. Give students the idea that one if one switch controls

one light bulb, we can control the amount of light needed. By switching on the lights needed for a particular task,

we can get the right amount of light required for a particular situation or job. All the other light bulbs that are not

needed are switched off. Get them to think if they are working in one corner of the room, all the lights there can

be switched on while the others can be switched off.

Learning activities worksheet b5_10 Low demand � This lesson aims to develop students’ understanding of the fact that unspecialised cells contain

thousands of genes, all of which are switched on. During the process of specialisation, genes are switched off and

only the genes needed by that particular type of cell remain switched on. Use the true and false questions in

activity 1 on the worksheet to check understanding. If students are keen, they could think about the genes that are

switched off and those that remain switched on in a particular type of cell, such as a palisade cell. (Genes for

making chloroplasts are switched ON, genes for making cytoplasm ON, genes for making a tail OFF, etc.)

Standard demand � Ask the question ‘What is a stem cell?’ Students discuss this in groups and then feed back

their findings to another group. Then get the groups of students to share their ideas in order to reach a unanimous

class decision about what stem cells are. Points agreed upon could be: stem cells are unspecialised cells; genes in

stem cells are all switched on; stem cells can become any type of cell, etc.

Teaching and learning notes: Activity 2 on the worksheet asks students to create a Venn diagram showing the

similarities and differences between the two types of stem cell in humans. It may be useful for them to use

additional resources such as the internet and textbooks.

B5_10 Cell specialisation and gene activity continued


High demand � Ask the students to work in pairs or threes to carry out research using the internet and other

published resources into stem cell therapy. They should find out more about potential future treatments using stem

cells and any treatments that are actually being used currently. Groups then share what they have found out with

each other. Use questions from Activity 3 of the worksheet.

Plenary suggestions Ask a volunteer to come up to the front of the class and choose an area of the lesson they feel confident about. Ask

the other students to ask this volunteer questions about their chosen area of the topic. When a wrong answer is

given, swap to a different student.

Student Book answers Q1 In the nucleus (on chromosomes).

Q2 Only the genes that are needed by that cell are switched on. If a cell tried to produce all the proteins used in

the body then it would not be able to function properly and it would be very wasteful.

Q3 The genes coding for those specific protein are switched on.

Q4 All the genes of the eight-cell embryo are switched on whereas not all the genes in the in the cells of the

16-cell embryo are switched on (due to specialisation).

Q5 Various, for example: stem cells can differentiate into any type of cell in the body, so could be used to replace

all kinds of diseased and damaged tissue. There is even the potential to grow whole organs, etc.

Q6 There is less chance of the organ being rejected by the receiver’s body. This means there is no need for anti-

immune drugs (or drugs to prevent rejection).


Q1 True

Q2 True

Q3 False – Genes code for proteins.

Q4 False – Only certain genes in a normal body cell are active.

Q5 False – When a gene is active it is said to be switched on.

Q6 True

Q7 False – Stem cells are able to differentiate into different types of cell.

Q8 False – Proteins are made in the cytoplasm of a cell.


Q1 Various explanations – the idea of genes being switched on and off should be included.

Q2 For the Venn diagram, the differences are the places and development stages at which the different types of

stem cell are found, and the kinds of cells they can become. For the similarities, the obvious one is that they are

both able to differentiate into other cells.


Q1 In the cytoplasm.

Q2 No more haemoglobin can be made.

Q3 No – they have no nucleus to divide.

Q4 Mitochondria – they use oxygen to make energy so could compete with haemoglobin to take up oxygen.



b5_10 Cell specialisation and gene activity

1 Protein-making in cells

Decide whether each of the following statements is true or false. Write correct versions of any false statements.

1 All body cells in a human contain 46 chromosomes. True/False

......................................................................................................................................

2 Chromosomes are made up of DNA. True/False

......................................................................................................................................

3 Chromosomes code for genes. True/False

......................................................................................................................................

4 All genes in a normal body cell are active. True/False

......................................................................................................................................

5 When a gene is active it is said to be switched off. True/False

......................................................................................................................................

6 Specialised cells only make certain proteins. True/False

......................................................................................................................................

7 Stem cells are unable to differentiate. True/False

......................................................................................................................................

8 Proteins are made in the nucleus of a cell. True/False

......................................................................................................................................

2 Specialisation of embryonic stem cells

1 In groups, discuss the question ‘Why don’t all the cells of a cow produce milk?’ See who can come up with the best explanation.

2 In groups, discuss what the two types of stem cell found in humans are and produce a Venn diagram showing similarities and differences between the two.

b5_10 Cell specialisation and gene activity continued


3 Stem cell therapy

Use the internet to find answers to the following questions:

1 Why do scientists want to use stem cells?

2 Why are doctors and scientists excited about human embryonic cells?

3 Have human embryonic cells been used successfully to treat any human diseases yet?

4 What is the best type of stem cell to use for therapy? What is Parkinson’s disease?

5 How are stem cells used in therapy for Parkinson’s disease?

6 What are the problems in using stem cell therapies?



b5_11 Stem cell cloning

Resources

Student Book pages 62–63 � Interactive Book: News clip ‘Babies that save lives’ � Homework pack b5_11


Learning outcomes B5.3.10 understand that ethical decisions need to be taken when using embryonic stem cells and that this work is

subject to Government regulation

B5.3.11 understand that, in carefully controlled conditions of mammalian cloning, it is possible to

reactivate (switch on) inactive genes in the nucleus of a body cell to form cells of all tissue types

Ideas about Science IaS 6.3 in many areas of scientific work, the development and application of scientific knowledge are subject to

official regulations

IaS 6.4 some questions, such as those involving values, cannot be answered by science

IaS 6.5 some forms of scientific research, and some applications of scientific knowledge, have ethical implications.

People may disagree about what should be done (or permitted)

IaS 6.6 in discussions of ethical issues, one common argument is that the right decision is one which leads to the

best outcome for the greatest number of people involved. Another is that certain actions are considered right or

wrong whatever the consequences

ICT focus: Using the internet to research stem cell therapies.


� understand the ethical decisions involved when using embryonic stem cells

� understand that it is possible to switch on inactive genes in the nucleus of a body cell to form cells of all tissue

types

Key vocabulary

embryonic stem cells �� adult stem cells �� differentiation �� therapeutic cloning

Stimuli and starter suggestions There is some overlap between this lesson and lesson b1_11 from the first biology module. The focus in this lesson

is on alternative ways to carry out stem cell research and the ethical issues involved. There is also an emphasis on

Government regulation of stem cell research. The starter activity suggestions are similar to those in b1_11 and may

be carried out now if they were not done then.

� There is an excellent 15-minute video that gives a good start to this topic. Find it using ‘eurostemcell’ in a search

engine. Students could make notes while watching it, including any questions that they want to ask afterwards.

� Alternatively you could search for a news item, either in print or on the internet, which provides some basic

information on stem cells. The NHS ‘Behind the news’ site is good for items of this type.

� Questions 1 to 3 in activity 1 of the worksheet can be used to check how much students remember from module B1.

Learning activities worksheet b5_11 Low demand � Initiate a discussion on the issue of website reliability. You may need to prompt students about

what to consider by asking them questions such as:

• How can you decide whether or not a website is a reliable, trustworthy source of information?

• How do you know how recent the information on a website is?

• Do you know who has written it and what their qualifications are?

• If you found the same information elsewhere on the internet, would you feel confident that it was correct?

Construct a class list of guidelines to help to decide whether a website is reliable or not.

Then place students in pairs or small groups for their Fact-finding mission. Using the internet and other library

resources, the groups should work together to gather answers to some or all of the 16 questions in task 4 of

worksheet activity 1. Stress the importance of documenting their sources and recording the information correctly.

This can lead to a summary project that demonstrates what they have learned about stem cell research and

therapies. Students should be prepared to share what they find out.

b5_11 Stem cell cloning continued


Teaching and learning notes: Internet research works best if it is focused on a few important questions and a few

suitable websites. You may want to reduce the type/number of questions for the lowest attaining students. If there

is not enough class time for the Fact-finding mission, it may be used as individual homework.

Standard demand � The main emphasis in this lesson is an exploration of the different ethical viewpoints that exist

around stem cell research. Discuss the idea that not everyone agrees that the potential of stem cells should be

exploited, and the reasons for this. Worksheet activity 2 gives students statements of different views to consider in

small groups. After the group discussion, students could write a paragraph explaining their own point of view.

If time allows, ask students to write a letter, speech or play, or create a visual representation about their personal

opinion on stem cell research. Encourage students to share their opinions and use what they have learned from

studying the use of embryonic and adult stem cells to support their point of view. Give all students the opportunity

to share their project and opinions with the whole class or in small groups.

High demand � Reproduce this passage to show students and then pose the questions below.

Imagine you live in a time and place where people no longer suffer from diseases like Parkinson’s, diabetes, heart

disease, cancer, organ failure or Alzheimer’s. Imagine that spinal cords can be replaced and that most forms of

paralysis have been eliminated. Imagine that nerves, muscles and even badly burned skin can be regenerated and

replaced. Now imagine that the source of this technology comes from something that can’t be seen with the human

eye. While this might sound like space-age technology that we see in science fiction books and movies, imagine

that it could actually be a reality.

1. How would this type of medicine/technology change the quality of life of human beings?

2. How much would you be willing to pay for this kind of medicine/technology?

3. Are there any negative effects that could be caused by having this kind of medicine/technology?

Activity 3 of the worksheet provides further questions.

Plenary suggestions Students make a bookmark to remind them of the different ways to make sure that the websites they use are reliable.

Student Book answers Q1 Embryonic stem cells can differentiate to give any type of cell in the body. This gives them great potential in

replacing damaged and diseased cells, and even growing whole organs.

Q2 For organ donation, to help prevent the need for organ donors/waiting lists.

Q3 For: Could be used to treat diseases and reduce suffering; could open up new fields of treatment; could remove

the need for transplantation. Against: Who would own the stem cells; embryos have to be destroyed to harvest

the stem cells; scientists playing God (unnatural).

Q4 It removes the need to use embryonic stem cells and could make cells that are an exact match for a patient.

Q5 Inactive genes have to be reactivated.

Q6 It provides cells with the potential to differentiate into any cell in the body, without the need to destroy embryos.


Q1 a) A cell that can differentiate into other cell types.

b) Embryonic stem cell and adult stem cell.

c) Embryonic stem cells come from embryos and can differentiate into any cell type. Adult stem cells are found

in the tissues of both adults and children and can differentiate into just a few cell types.

d) Tissues such as bone marrow, umbilical cords, skin tissue and so on.

Q2 Embryos, eight, research, damaged, organs, donors

Q3 B, C and D


Pluripotent – able to differentiate into any cell type – but unable to form a whole organism.

Totipotent – able to differentiate into any cell type and able to form a whole organism (the zygote and all the cells in

an 8-cell embryo are examples of totipotent cells).

Multipotent – able to differentiate into a limited number of cell types (adult stem cells).



b5_11 Stem cell cloning

1 Stem cells in research

1 a) What is a stem cell?

......................................................................................................................................

b) Name the two types of stem cells in humans.

......................................................................................................................................

......................................................................................................................................

c) What is the difference between these two types of stem cells?

......................................................................................................................................

......................................................................................................................................

d) Where in the body can you find adult stem cells?

......................................................................................................................................

2 Fill in the blanks in the passage below using words from the box.

cancer donors stem cells sixteen embryos

doctors eight damaged four research organs adults

Embryonic stem cells come from ........................ at the .......................... cell stage. They

are used in ...................... to help scientists to develop new cells to replace ......................

cells. Stem cells have the potential to become whole ....................... The advantage of

using stem cells like this is that there will be no more need for . ................ for transplants.

3 Which of the following can be used to accurately complete the sentence below? Circle one or more letters.

Stem cells have the potential to be used:

A to treat chickenpox

B to replace cells lost through disease

C to create organs for transplant

D to replace burned tissue



4 Fact-finding mission

Work in pairs or small groups. Use library and internet resources to learn as much as you can about stem cell research and current stem cell therapies, in order to answer the questions below. For each answer, be sure to document your information sources, as all good scientists do. Be prepared to share what you have learned with your classmates. All group members must contribute.

1 What is the definition of a stem cell?

2 What is the difference between adult stem cells and embryonic stem cells?

3 What is a blastocyst?

4 What parts of the human body contain stem cells?

5 What is a stem cell line?

6 What are the advantages of using embryonic stem cells rather than adult stem cells?

7 What are the advantages of using adult stem cells rather than embryonic stem cells?

8 How can stem cells be used to treat diseases and injuries? List some current uses.

9 What are some of the potential ways that stem cells might be used to treat diseases and injuries in the future?

10 Why is there controversy about using embryonic stem cells?

11 Why has Government funding for stem cell research been limited?

12 Describe the process used to harvest embryonic stem cells.

13 Describe the process used to harvest adult stem cells.

14 Describe the process of using adult stem cells to treat one particular disease.

15 What types of human tissues, organs or other cells have been grown from human stem cells so far?

16 List any other interesting facts you learned about stem cell research.



2 Ethical issues

1 Group the following statements into those that support embryonic stem cell research, those that do not support it, and those that are neutral. Be prepared to defend your choices.

A The two types of stem cell are embryonic

stem cells that come from embryos and

adult stem cells from adult tissue.

B Scientists around the world are working

on techniques involving stem cell

therapy.

C Many stem cells used in research come

from aborted embryos or spare embryos

from fertility treatment.

D Embryos are living and using them for

research is the same as murder.

E Scientists believe the best stem cells come

from embryos.

F Stem cells are also found in some adult

organs. They have not taken on a final

role and have the potential to become

different specialised cell types within

that organ.

G It may be possible to use stem cells to

generate healthy tissue to replace tissue

that has become damaged, e.g. by burns

or spinal cord damage.

H Stem cells could be used to treat

diseases such as Parkinson’s disease,

heart disease and diabetes.

I Adult stem cells are more limited in their

ability to become different cell types than

embryonic stem cells.

J Stem cells may provide a useful way to

test the effects of new experimental

drugs.

K Studying stem cells may provide clues

about how the tissues of the body develop

and how diseases take hold.

L The umbilical cord provides a good

source of stem cells.

M When a stem cell divides, each new cell

has the potential to either remain a stem

cell or become a specialised cell.

N Some types of stem cells can be taken

from other places, including adult

tissues, without the need to kill

embryos.

O It is more important to treat someone who

is in a lot of pain than to worry about the

rights of an embryo.

P Stem cells can be grown and

transformed into specialised cells such

as muscle cells or nerve cells.

Q Adult stem cells from umbilical cord blood

and bone marrow are routinely used in

medical therapies.

R Unused embryos will be discarded

anyway, so why not use them for

research?

3 Uses of stem cells

1 Are embryonic stem cells:

A pluripotent B totipotent C multipotent?

Find out what each of these terms means in order to answer the question and then explain your answer.

2 Find out what ‘saviour siblings’ are and how they can be used to treat disease. From the information you find, decide whether saviour siblings are a good or a bad idea and justify your opinion.

Then answer these questions:

a) Were your sources of information reliable? How do you know?

b) Try to come up with an alternative argument, justifying the opposite point of view.

b5 module introduction - sows - homegrowth+and... · · 2012-06-29b5 module introduction ... by...

Documents