grade 8: life science 3 unit 8l.3 micro-organisms and food ... · pdf file173 | qatar science...

173 | Qatar science scheme of work | Grade 8 | Unit 8L.3 | Life science 3 © Education Institute 2005

GRADE 8: Life science 3

Micro-organisms and food

About this unit This short unit is the third of six units on life science for Grade 8.

This unit is designed to guide your planning and teaching of lessons on life sciences. It provides a link between the standards for science and your lesson plans.

The teaching and learning activities should help you to plan the content and pace of lessons. Adapt the ideas to meet your students’ needs. For extension or consolidation activities, look at the scheme of work for Grade 9 and Grade 7.

You can also supplement the activities with appropriate tasks and exercises from your school’s textbooks and other resources.

Introduce the unit to students by summarising what they will learn and how this builds on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and 'real life' applications.

Previous learning To meet the expectations of this unit, students should already know that individual micro-organisms are too small to see with the unaided eye. They should already be able to name the major groups of micro-organisms. They should already understand the importance of micro-organisms in nitrogen fixation, decomposition and nutrient recycling.

Expectations By the end of the unit, students give examples of the use of micro-organisms in food production. They plan, collect data and make observations in a systematic way, identify patterns, consider the validity of evidence, the extent to which it supports a prediction, and draw conclusions.

Students who progress further know that fermentation by micro-organisms produces alcohol.

Resources The main resources needed for this unit are: • samples of food made using micro-organisms (e.g. blue cheese, vinegar) • live yoghurt, sterilised milk, tap funnel • slices of bread, sample of fresh yeast • active yeast and sugar suspension or bread dough

Key vocabulary and technical terms Students should understand, use and spell correctly: • bacteria, fungi, yoghurt • yeast, fermentation

UNIT 8L.3 5 hours


Standards for the unit

5 hours SUPPORTING STANDARDS CORE STANDARDS

Grade 8 standards EXTENSION STANDARDS

8.11.1 Know that micro-organisms are used in making foods such as bread, cheese and yoghurt.

7.10.2 Know that micro-organisms in soil decompose organic matter and dead organisms and help to recycle nutrients. 8.11.2 Know that micro-organisms are used to make beer and wine. 9.12.4 Give the word equations for anaerobic

respiration; explain the process as a cellular biochemical reaction in which a respiratory substrate reacts without oxygen to release energy and produce carbon dioxide and alcohol or lactic acid; know that when carried out by micro-organisms, this is termed fermentation.

4 hours

Micro-organisms in food production

1 hour

Micro-organisms in wine and vinegar production 8.1.1 Plan investigations, controlling variables and collecting an appropriate

range of evidence, using appropriate techniques to ensure accuracy, identify patterns in observations and data, draw generalised conclusions and test predictions.

Unit 8L.3


Activities

Objectives Possible teaching activities Notes School resources

Recap with students what they remember about the major groups of micro-organisms from Grades 6 and 7. Ask students to work in small groups to produce a list of how micro-organisms are harmful and how they are helpful (using their prior knowledge). Take feedback from the groups to build up a balanced picture of micro-organisms as having a huge impact on all our lives – both positive and negative.

Explain that fungi and bacteria are the two groups of micro-organisms used in food production. Provide a number of cards with names of foods on and ask students to sort them into food made using bacteria and food made using fungi (e.g. yoghurt, cheese, vinegar, bread, wine, soy sauce and blue cheese). Show students samples of some foods made using micro-organisms (e.g. blue cheese) to look at with a hand lens.

Prepare word cards in advance.

Use this column to note your own school’s resources, e.g. textbooks, worksheets.

Let students make yoghurt. Provide a starter culture of live yoghurt and sterilised milk. Ask students to add a spoonful of yoghurt to several test-tubes of milk and keep these test-tubes at different temperatures for 8 hours or overnight to see how temperature affects yoghurt production.

Milk thickens as yoghurt is made; ask students to measure changes in viscosity by timing how long it takes the yoghurt to pass through a tap funnel. Alternatively, ask them to measure changes in pH as the yoghurt is made, using electronic datalogging equipment.

Safety: Do not allow students to taste the yoghurt they make in the laboratory. If you can arrange to use a food preparation area, students could make and taste their yoghurt.

ICT opportunity: Use of datalogger.

Enquiry skill 8.1.1

4 hours

Micro-organisms in food production Know that micro-organisms are used in making foods such as bread, cheese and yoghurt.

Plan investigations, controlling variables and collecting an appropriate range of evidence, using appropriate techniques to ensure accuracy, identify patterns in observations and data, draw generalised conclusions and test predictions.

Show students microscopic images of yeast and a sample of fresh yeast. Explain that yeast is single celled and that this is unusual for a fungus. Ask students how yeast is used in bread-making and clarify that it makes the dough rise. Remind students that yeast is a living thing (a microscopic image will show new yeast cells budding from mature ones) and ask them what yeast might need to live. Ask students what gas yeast produces that makes bread dough rise (bearing in mind that yeast is a respiring, living thing). Challenge students to design a technique for testing this gas and let them try out and refine their ideas.

Let students investigate what affects how much carbon dioxide yeast produces (e.g. amount of sugar, temperature, pH). Students could either measure the height of bread dough or collect bubbles of carbon dioxide from a yeast and sugar suspension.

Collect all the class’s results and ask students to present them as line graphs and describe any patterns they can see. Ask students to consider whether there was sufficient evidence to draw conclusions and if there are any surprising results (e.g. too much sugar may reduce carbon dioxide production).

If using dried yeast, mix it in advance of the lesson and make sure it is active before you start the investigation.

Enquiry skill 8.1.1

Unit 8L.3


Objectives Possible teaching activities Notes School resources

1 hour

Micro-organisms in wine and vinegar production Know that micro-organisms are used to make beer and wine.

Explain that carbon dioxide is not the only product when yeast respires and define fermentation. Ask students what they think happens to the alcohol produced when yeast is used to make bread dough rise. Show students diagrams that illustrate wine and beer production and explain that grapes ferment because yeast is found naturally growing on grape skins.

Challenge students to research how vinegar is made using reference books and the Internet. In their report students should include: • the history of vinegar making; • the type of micro-organism used to make vinegar; • different raw materials for making vinegar; • a step-by-step description of vinegar production; • an explanation of why vinegar is not alcoholic.

ICT opportunity: Use of the Internet.


Assessment

Examples of assessment tasks and questions Notes School resources

Complete the table below by putting a tick in one or both columns:

Food Made using fungi? Made using bacteria?

Yoghurt

Cheese

Soy sauce

Bread

Wine

Vinegar

Assessment Set up activities that allow students to demonstrate what they have learned in this unit. The activities can be provided informally or formally during and at the end of the unit, or for homework. They can be selected from the teaching activities or can be new experiences. Choose tasks and questions from the examples to incorporate in the activities. Here are instructions for making blue cheese:

1. Add rennet to 1 litre of milk so that it curdles and drain the curds.

2. Sprinkle 2 teaspoons of salt into the curds.

3. Mix 1 teaspoon of blue cheese with 50 ml of clean water.

4. Add this to the curds, mix thoroughly and place in a sterile handkerchief.

5. Press overnight.

6. Use a sterile steel rod to make holes in the cheese every 3 cm.

7. Place on a rack at 10 °C for 50 days.

a. What type of micro-organism makes cheese blue?

b. At which step is this micro-organism added in the instructions above?

c. Why is it important to sterilise the handkerchief and steel rod used in the instructions?

d. Suggest a reason why holes are made in the cheese.

Unit 8L.3

grade 8: life science 3 unit 8l.3 micro-organisms and food ... · pdf file173 | qatar science...

Documents