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Preliminary Biology Topic 2 “Patterns in Nature”copyright © 2005-22008 keep it simple sciencewww.keepitsimplescience.com.au

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What is this topic about?To keep it as simple as possible, (K.I.S.S.) this topic involves the study of:1. LIVING CELLS & THEIR STRUCTURE

2. CHEMICALS MOVE IN & OUT THROUGH MEMBRANES3. NUTRITION IN PLANTS & ANIMALS

4. GAS EXCHANGE & INTERNAL TRANSPORT5. CELL DIVISION FOR GROWTH & REPAIR

but first, an introduction...CellsAll living things are composed of microscopic“lumps” called cells.

Some organisms are composed of just a single cell.

All familiar organisms are made of many cells; forexample, your body is composed of approximately300 billion cells... you are “multicellular”.

Each cell is a tiny sac of “protoplasm”... water witha complex mixture of chemicals dissolved in it,plus many structures called “organelles” (littleorgans).

Plants and animals have cells with a fewimportant differences. Organisms such as fungiare different again, while bacteria have a totallydifferent cell structure.

Organization of a Multicellular Organism

A building is not just a pile of bricks, and anarmy is not just a rabble of soldiers. Each has astructure, and levels of organization soeverything works together.

Similarly, your body is not just a big heap ofcells. It has levels of organization...

a CELL is the basic unit of any living thing.

A number of similar cells working together is a...

TISSUE. (e.g. muscle tissue, bone tissue.)

Various tissues are combined to make an...

ORGAN. (e.g. heart, kidney, liver.)

A number of organs work together for a specificpurpose. This forms a...

SYSTEM. (e.g. digestive system.)

Finally, all the body systems working togetherform...

YOU - a functioning, multicellular organism.

In this topic you will study the basics of the structure and functioning

of living things.

GENERALIZED DIAGRAM OF A LIVING CELL

“Membrane” on the outsidecontains the cell , and

controls what goes in or out

Organelles

Cytoplasm is ajelly-llike liquidwhich fills the

cell

Preliminary Biology Topic 2

PATTERNS in NATURE

CellDivision

Vital Body

Systems

Cell structure &

Chemistry




2

Structure of

Membranes

Diffusion &

Osmosis

Surface Areato

Volume Ratio

Photosynthesis&

Respiration

Structure &Function of

Leaf

Plant &Animal Cells

Reasons for Cell Division

PATTERNSin

NATURE

Living Cells&

Their Structure

ChemicalsMove In & Out

ThroughMembranes

Nutritionin

Plants & Animals

Gas Exchange&

Internal TransportCell Divisionfor

Growth & Repair

CellOrganelles

GasExchange

in Animals

Circulation in Animals

GasExchange &Transport in

PlantsMitosis

Digestionin

Animals

CellTheory

CellChemicals

CONCEPT DIAGRAM (“Mind Map”) OF TOPICSome students find that memorising the OUTLINE of a topic helps them learn and remember

the concepts and important facts. As you proceed through the topic, come back to this page regularly to see how each bit fits the whole.

At the end of the notes you will find a blank version of this “Mind Map” to practise on.




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1. LIVING CELLS & THEIR STRUCTURE

The Cell TheoryThe “Cell Theory” is one of the fundamentalconcepts in Biology. It simply states:

• All living organisms are composed of cellsor are the product of cells. (e.g. viruses)

• All cells are produced from pre-existing cells.

The evidence supporting the Cell Theory has comealmost entirely from the use of microscopes toexamine living things.

Our knowledge of cell structure and function hasdeveloped as the technology of microscopesadvanced over the last 300 years or so.

Initially, only light microscopes were available, butsince the 1930’s electron microscopes haverevealed more detail of cell structure and function.

Comparison: Light & Electron ‘Scopes

Light ElectronMicroscope Microscope

How the beam of light beam of electronsimage focused by focused by magneticis formed glass lenses fields

Magnification generally about up to 1,000,000 X500 X. (500 times moreMaximum powerful)about 2,000 X

Resolution about 0.2 μμm about 0.0002 μμm(ability to see (1,000 times betterfine details) detail)

micrometres (μμm) 1 μμm = 0.000001(10-6)metre.

1 micrometre is 1/1000 of a millimetre

How Big Are Cells Anyway?

Typical Plant Cell50-100 μμm

Typical Animal Cell5 - 20 μμm

Bacterial Cells1 - 5 μμm

History of Our Knowledge of CellsRobert Hooke, 1665Hooke is credited with being the first person tosee cells andname them.Using aprimitivemicroscope, helooked at apiece of cork(dead tree bark)and saw tiny“boxes” like therooms andcompartmentsof a gaol ormonastery.(hence “cells”)

Anton van Leeuwenhoek, 1676van Leeuwenhoek used a very simple microscope,but it was equipped with an excellent lens, throughwhich he saw living micro-organisms swimmingaround in a drop of water.

Over the next 150 years, microscopes improved,and it was suspected that cells were present in allliving things.

Robert Brown, 1827Brown was the first to discover structures insidecells. He discovered and described the nucleusinside plant cells.

By about 1840, the “Cell Theory” was becomingaccepted by most biologists, because cells wereobserved in every organism studied. LouisPasteur’s discoveries showed that infectiousdiseases were caused by “germs”, which weremicroscopic, cellular organisms.

Rudolf Virchow, 1859 and Walther Flemming, 1879

Between them, these two German scientistsclarified the process of cell division, by which cellsproduce more cells. This established the principlethat all cells come from pre-existing cells.

In the 20th century, the electron microscopeopened up our knowledge of the fine detail of cellstructures and their functions.

SSCCAALLEE:: 110000 μμmm((00..11 mmmm))

Sketch ofHooke’s

microscope




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The Major Differences Between Plant & Animal CellsPlant cells have a tough CELL WALL on the outside of their cell membrane.

Many plant cells contain a large VACUOLE. Animal cells rarely have vacuoles, and if present they are small.

Many plant cells contain CHLOROPLASTS. These are green in colour because they contain the pigment chlorophyll.

Chloroplasts are the sites of PHOTOSYNTHESIS, where plants make food.

Note: not all plant cells have chloroplasts... for example, cells in the underground roots cannotphotosynthesise, so do not contain any chloroplasts.

What the Electron Microscope RevealsThe superior magnifying power and resolution of the electron microscope has given us a muchmore detailed knowledge of the cell and its organelles. The diagram below is a sketch of a plant

cell similar to the one above, but with the added details that the electron microscope has revealed.The extra organelles shown are generally NOT visible with a light microscope.

Generalized ANIMAL CELL

SmallVacuoles

(if any at all)

CELL WALL(outside of membrane)

CHLOROPLASTS(green colour)

NUCLEUS

CELLMEMBRANE

CYTOPLASM

Cell WallCell MembraneVacuole

Chloroplast internal structure

Stacks of flat membranes(grana) contain the

chlorophyll

Mitochondrion.Site of cellularrespiration

Lysosomes

Golgi apparatus

NucleusExtra detail revealed

Endoplasmic ReticulumA network of membranestructures connected to

nucleus & extendingthroughout the cytoplasm

The tiny Ribosomes areoften attached to the E.R.

Cell Organelles Visible with a Light MicroscopeYou may have done practical work in class to use a light microscope to view cells in living things.

GeneralizedPLANT CELL

LargeVACUOLE

There are probably no actualcells which looks just like these.

Real shapes vary greatly.




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The Organelles... Structure & Function

Nuclear membranewith pores, for

RNA exit

NucleolusRNAmanufacture

Nuclear material“chromatin”.

(Chromosomesunwound andspread out)

NUCLEUSThe NucleusThis is the control centre of the cell.

Inside the nucleus are the chromosomescontaining DNA, the genetic material.There is often a nucleolus present. This isthe site for production of RNA, a“messenger” chemical which leaves thenucleus carrying instructions to otherorganelles. The nuclear membrane hasholes or “pores” to allow RNA to exit.

Mitochondria (singular: mitochondrion)

This is where cellular respiration occurs

Glucose + Oxygen Carbon + Water + ATP(sugar) Dioxide

The ATP produced by respiration carrieschemical energy all over the cell to power allthe processes of life. The mitochondria aretherefore, the “power stations” of the cell,converting the energy of food into the readilyusable form of ATP.

Inside a mitochondrion is a folded membranewith many projections (“cristae”). Thisstructure provides a greater surface area,where the enzymes (control chemicals) forrespiration are attached in correct sequencefor the steps of the process.

This structure helps the organelle do its job more efficiently.

Innermembranefolded into

“cristae”with

respirationenzymesattached

Endoplasmic Reticulum (E.R.)

E.R. is a network of membranes which formchannels and compartments throughout thecytoplasm of the cell. Its function can be compared tothe internal walls of an office building which divide thebuilding into “rooms” where different operations canbe kept separate so that each does not interfere withothers.

The E.R. structure provides channels for chemicalsand “messengers” to travel accurately to thecorrect locations, and for chemical production tooccur in isolation from other operations.

This structure helps cells functionOften found attached to the E.R. are the tinyRibosomes. These are the sites of productionof proteins, the main structural and functionalchemicals of living cells. RNA “messengers” fromthe nucleus attach to a ribosome to make thespecific proteins that the cell needs.

ENDOPLASMICRETICULUM

RIBOSOMESattached to membranes

Membranes

Membranes enclosechannels and “rooms”

MITOCHONDRION

Outermembrane

The Cell Membrane This is not only the boundary of the cell, but also

controls what goes in or out of the cell. This isstudied in more detail in the next section.




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The Importance of MembranesExcept for the tiny ribosomes, all the cell organelles are built from,

and surrounded by, membranes.

The membranes provide:-• the infrastructure of the cell.• channels for chemicals to move through.• packaging for chemicals which need to be stored.• points of attachment for chemicals (“enzymes”).• control over what moves in or out of each

organelle, and in or out of the entire cell.

The “membrane-bound” organelles help the cell’s various functions to be carried out with greater efficiency.

Having these membrane-based organelles is the defining characteristic ofthe “Eucaryotic” group of organisms, which includes all plants and animals.

Bacterial cells do NOT have all the membrane-type organelles, and can only operate efficiently by being very small.

Chloroplasts

Chloroplasts are found only inphotosynthetic plant cells. The electronmicroscope has revealed that thechloroplast is not just a bag of chlorophyll,but has an organized internal structurewhich makes its functioning moreefficient.

The “grana” are stacked membrane sacscontaining chlorophyll, which absorbs thelight energy for photosynthesis. This light-capturing step is kept separate from the“stroma” zone, where the chemicalreactions to make food are completed.

CHLOROPLAST

Doublemembraneenvelope

Membrane stacks(“grana”)

containing chlorophyll

“Stroma”zone

The Golgi Apparatus is a semi-circulararrangement of membranes which areconcerned with packaging chemicals intosmall membrane sacs (“vesicles”) forstorage or secretion.

One type of “vesicle” produced by a GolgiBody is the Lysosome. These membranesacs contain digestive enzymes which candestroy any foreign proteins which enterthe cell.

Lysosome enzymes also rapidly digest thecontents of a cell which has died, so thatyour body can clean up the remains andreplace the dead cell.

GOLGI BODY Curvedmembrane

sacs

Vesicles pinch-oofffor storage or

secretion

Lysosomesform this

way




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Worksheet 1Cell Theory & Cell Structure

Fill in the blank spaces and diagram labels.

The “Cell Theory” states that(a)................................ are composed ofcells, and that all cells are produced from(b)......................................................

Our knowledge of cells is due mainly to thetechnology of (c)..............................................

The (d)....................................... of amicroscope refers to its ability todistinguish fine details. The(e)................................. ‘scope is far superiorin both (d) and (f)...................................

The man credited with being the first to seecells was (g).....................................................

Label the parts of this plant cell seen with asimple light microscope.

List 5 additional organelles normally onlyvisible with an electron microscope.(p)........................................q).........................................r)..........................................s)..........................................(t).........................................

Complete these lists to describe thefunctions of the organelles.Organelle FunctionCell membrane (u)

(v) Partitions cell into channels &

compartments

Golgi apparatus (w)

(x) Cellular respiration.

(y) Photosynthesis

Cell wall (z)

(h).................................

(i).................................

(j).................................(k).................................

(m).........................

(l).................................(inside (k)

WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES

Practice Questions for this sectionare included in Worksheet 3

Which TWO parts of this plant cell woulddefinitely never be seen in an animal cell?

(n)........................................ and

(o)..................................


The Chemicals That Cells Are Made From

CARBOHYDRATES include the sugars and starch.

monosaccharides (mono = one)are simple sugars such as glucose C6H12O6

disaccharides (di = two)are sugars made from TWO monosaccharidesjoined together, such as “table sugar” (sucrose).

polysaccharides (poly = many)are huge molecules made from thousands ofsugar molecules joined in chains or networks.Examples are:Starch... made by plants, to store excess sugar.Glycogen... made by animals, to store sugar.Cellulose... made by plants as a structuralchemical. The CELL WALL of a plant cell is madefrom cellulose.

Uses of CarbohydratesSugars are energy chemicals. Glucose is made byplants in photosynthesis, and is the “fuel” forcellular respiration to make ATP to power all cells.

Starch & Glycogen are polymer molecules used tostore sugars as a food reserve. Starch is the mainnutrient chemical in the plant foods we eat.

Cellulose & Lignin are polymers of sugar used byplants structurally. Cellulose makes the tough cellwall of all plant cells. Lignin is a strong materialused to reinforce the walls of “veins” in plants.



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2. CHEMICALS MOVE IN & OUT THROUGH MEMBRANES

INORGANIC CHEMICALSThese include small simple

molecules like water (H2O) andcarbon dioxide (CO2), as well asmineral ions such as calcium,

nitrate, phosphate, chloride, etc.

Although these are oftenconsidered of lesser importance,

you should remember that all livingthings are 75%- 95% water.

Polysaccharide.Small part of aStarchmolecule

PROTEINSare the main structural chemicals of organelles, cells, bone, skin & hair.

Life is built from protein.

Proteins are polymers, made from aminoacid molecules joined in chains.

Amino acidmolecules

Part of a protein molecule...a chain of amino acids

LIPIDSare the fats and oils.

All cell membranes are built fromlipid & protein.

Lipids are used as a way to storeexcess energy food.

Carbohydrates can be convertedto fat for storage.

NUCLEIC ACIDS (DNA & RNA)are the most complex of all. DNA is the genetic information of every cell. RNA is the “messenger” sent out from the nucleusto control all cellactivities.

DNA is a hugepolymer of sugars,phosphate and“bases” coiled in adouble helix shape.

ORGANIC CHEMICALS“Organic” chemicals are based on the elementcarbon, which can form chains, rings andnetworks and so build the very complexmolecules needed to make a living cell. Many are “polymers” made by joining togethermany smaller molecules.

There are four main categories to know about...

Monosaccharidesugarmolecules

Disaccharidesugar




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Identifying Chemicals in TissuesYou may have done laboratory work to learn somesimple chemical tests which identify importantsubstances. These tests all rely on a “reagent”which changes colour.

To keep it simple (K.I.S.S.), learn these:

Cell Test Colour in PositiveChemical Reagent Pure water Result

Glucose Benedict’s pale blue yellow or solution orange

Starch Iodine yellow dark bluesolution brown or black

Protein Biuret blue purple

You will have used one or more tests on livingtissue and examined the cells with a microscope.

For Example: if tissue scraped from a fresh potatois mounted on a slide with a simple “contraststain” (like methylene blue) the cells look like this:

If a drop of iodine solution is added, the same cellschange as shown:

Once you have an understanding of the mainchemicals that cells are made from, you need torealize that all of these substances, or their rawmaterials or waste products, are constantlymoving in or out of a living cell.

TO DO THISCHEMICALS MUST CROSS

THE CELL MEMBRANE

The Structure of the Cell MembraneThe electron microscope and other modernanalysis methods have revealed the structure of themembranes which surround a cell and form most ofthe cell organelles.

The membrane is extremely thin; just two moleculesthick. The basic chemical unit is a “phospholipid”molecule; a lipid (fat) with phosphate groups attached.Each molecule has two distinct ends; one which isattracted to water molecules (“hydrophilic”) and theother is repelled by water (“hydrophobic”).“Hydro”=water. “philic”=to like. “phobic”=hate / fear.

Two layers of phospholipids form each membrane.The molecules cling to each other, and line up withtheir hydrophilic ends outwards. The water-lovingends are attracted to the watery environment bothinside and outside the cell.

Their hydrophobic ends are repelled from thewatery surroundings, and cling together inside themembrane itself.

It is like a thin layer of oil floating on water. It is fluidand flexible, but clings together forming anunbroken “skin” on the surface.

Other molecules are embedded in the phospholipidbilayer. They are mostly proteins, many withcarbohydrates attached.

These other molecules have various functions:

• “receptors” for messenger chemicals.• identification markers, so your body knows its own cells from any foreign invaders.

• to help chemicals get through the membrane.

POTATO CELLS

POTATO CELLSWITH IODINE

Organellesfaintlyvisible

Cell walls

Organelles turn black

This indicates thepresence of starch

inside the organelles(these are storage

vacuoles)

Membrane proteins

OOnnee pphhoosspphhoolliippiidd

hhyyddrroo--pphhiilliicc

-pphhoobbiicc

MEMBRANE STRUCTUREOutside of cell

Inside of cell

Double layer ofphospholipid molecules




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How Chemicals Pass Through MembranesThe cell membrane as the boundary of a cell is a bit like growing a plant hedge as

the boundary of a field. It stops the cows and horses getting out, but a mouse, or a lizard, can easily crawl through it.

Similarly, a membrane is “semi-permeable”; it prevents most (especially large)molecules getting through, but allows others to pass through easily. Small

molecules like water (H2O), oxygen (O2) and carbon dioxide (CO2) pass freelythrough the membrane like a lizard through a hedge.

To understand how this happens, you must learn about the processes of DIFFUSION & OSMOSIS.

Diffusion occurs in every liquid or gasbecause the atoms and molecules areconstantly moving. The particles “jiggle”about at random in what is called“Brownian motion”. (Named for itsdiscoverer Robert Brown, the same manwho discovered the cell nucleus.)

Imagine a water solution containing adissolved chemical, but it is NOT evenlydistributed... it is more concentrated in oneplace than elsewhere. As the moleculesjiggle about at random, they willautomatically spread out to make theconcentration even out. This process iscalled DIFFUSION.

In a living cell, there is often a“concentration gradient” from theoutside to the inside of the cell.

For example, because a cell keepsconsuming oxygen for cellularrespiration, the inside of the cell usuallyhas a low concentration of O2 dissolvedin the water of the cytoplasm. On theoutside, there may be a lot of O2.

DIFFUSION DRIVES MOLECULES THROUGH THE MEMBRANES

along the concentration gradient.

DIFFUSION of SMALLMOLECULES into a CELL

If the molecules can cross the membrane,diffusion will cause them to move from

higher to lower concentration.

Higherconcentrationoutside cell

Lowerconcentration

insideHighconcentration

Lowerconcentration

Equal concentrationthroughout

To start with, thedissolved material is

not evenlydistributed.

Diffusion causes thedissolved solute to

spread outuniformly.

Diffusion



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OsmosisOsmosis is a special case of diffusion, which occurs when the concentration

gradient involves dissolved molecules or ions which CANNOT get through the membrane.

The opposite situation can also happen.A cell’s cytoplasm contains manydissolved chemicals. If the outsideenvironment around the cell is morewatery (less concentrated in dissolvedsubstances) then osmosis will causewater to diffuse inwards.

This can cause cells to “pump up” withwater and helps maintain their shape. Itcan also cause problems for organismsliving in fresh water environments.

For example, consider a cell which issurrounded by a solution containing a lotof dissolved sugar. The sugar cannotdiffuse through the membrane to equalizethe concentrations. In such a situation,water (which can go through themembrane) will diffuse toward the highsugar concentration, as if attempting toequalize by diluting the sugar.

In this case, the cell will lose water andmight shrink and shrivel up. This can bea problem for animals living in saltwater.

Sugar cannot getin through the

membrane

OSMOSISWater diffuses

OUT of cell

H22OH22O

H22O

Dissolved chemicalscannot diffuse out...

...so water diffuses intothe cell.

This is how plants absorb water into theirroots, even when the soil seems almost dry.

H22O

H22OH22O

Highconcentration

of sugaroutside cell

Comparison of Diffusion and OsmosisDiffusion is the movement of dissolved chemicals from an area of higher

concentration toward a lower concentration area. The movement follows the“concentration gradient” of the molecules in question.

Osmosis is a special case of diffusion. It is the diffusion of WATERthrough a semi-permeable membrane, against the concentration gradient of solutes.

It occurs when the solutes cannot penetrate the membrane, but the water can.Other Ways Substances Get Through Membranes

Diffusion and Osmosis are vitally important for manychemicals (especially water) to get in and out of cells.Diffusion and osmosis happen automatically andwithout the cell having to use any energy. We saythese are “passive transport” processes.

What about all the other important chemicals whichcannot get through the membrane? Many proteins,carbohydrates and other molecules regularly moveinto or out of cells. How do they get in or out?

Cells have other ways to deliberately movesubstances across the membrane apart fromdiffusion and osmosis. One such processinvolves the membrane proteins carrying things.

These “other” ways to transport materials acrossmembranes require the cell to use energy (ATPfrom cellular respiration) to move substances. Wesay these are “active transport” processes. Youdo not need to know the details at this stage.




12

1 unitsides

2 unitsides

3 unitsides

Surface Area:Six squares, each 1x1

SA = 6x1x1= 6 sq.units

Volume = lxbxh= 1x1x1= 1 cu.unit

Ratio of SA to Volume

SA/V = 6 / 1

SA = 6vol





SA/V = 96 / 64

SA = 1.5vol

Cells must feed their Volume,through their Surface Area

The Importance of the Surface Area to Volume RatioWhy are cells so small?

The answer requires a mathematical study...

Consider this series of cubes of increasing size:

But, all cells have to get whatever theyneed in through their cell membrane, andthe size of the membrane is all aboutsurface area.

As any cell gets bigger, it becomes moreand more difficult for it to get enoughfood, water and oxygen because itsSA/Vol. ratio keeps shrinking. Getting ridof waste products also becomes moredifficult.

Large cells are impossible... all single-celled organisms are microscopic, and alllarger organisms are multi-cellular. Theonly way to be big is to have lots of smallcells.

Notice that as the cubes get larger:

• Surface Area increases, and...

• Volume increases, but...

• SA / Vol Ratio DECREASES, because the volume grows fasterthan the surface area.

This pattern is the same for any shape...as any shaped object gets bigger, theratio between its Surface Area and itsVolume gets smaller.

What’s this got to do with cells?

The amount of food, oxygen or othersubstances a cell needs depends on itsvolume... the bigger the cell, the more itneeds according to its volume.





SA/V = 54 / 27

SA = 2vol





SA/V = 24 / 8

SA = 3vol

4 unitsides




13

Fill in the blank spaces.Simple, small molecules and ions (e.g.water, nitrate) are known as(a)........................ compounds, asopposed to “organic” compounds whichare based on the element (b)................,and include:-

• (c)............................... which arepolymers of amino acids

• Lipids, which are found structurally inthe cell (d)...................................... andare also used as (e)..........................................................................

•(f)......................................... whichinclude the sugars & starches.

One of this group, glucose, has chemicalformula (g).............................. and is the“food” made during the process of(h)................................... It is also the fuelfor (i)..................................... (organelle) tomake ATP.

• Nucleic acids, of which (j).................... is the best known.

If Benedict’s solution turns from blue toyellow, this proves that(k)....................................... is present.

Protein can be identified by(l).................................... reagent, and ifstarch is present iodine solution will turnfrom (m) .................... to (n).......................

The cell membrane is made from adouble layer of (o)......................................molecules, with various proteinsembedded.

The membrane is said to be “semi-(p)........................................”

Diffusion is a process where moleculesmove from a place of(q)............................ concentration,towards a (r)...................... concentration.

Osmosis is the diffusion of(s).......................... molecules only,against the solute concentration(t)........................., when the solute isunable to get through a membrane.

Diffusion & Osmosis are both examplesof (u)................................. transport,because the cell does not need to use(v).............................. to make thingsmove.

As any shape gets larger, its(w)......................................... ratio getssmaller. This is why all cells are small. Alarge cell needs chemicals in proportionto its x)..............................................However, it must get substances inthrough its y)............................................,the size of which is measured by itsz)............................ .....................................

The only way for living things to belarge, is to have aa)....................................cells, NOT by having ab)............................cells.

WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES

Worksheet 2 Chemicals & The Cell Membrane



14


Multiple Choice1. The man credited with the discovery of thecell nucleus was:A.Robert Hooke.B. Anton van Leeuwenhoek.C. Robert Brown.D. Louise Pasteur.

2. The organelle least likely to be seen with alight microscope is:A. Mitochondrion.B. Vacuole.C. Nucleus.D. Chloroplast.

3. The cell structure never found in an animalcell is:A. cell membrane.B. cell wall.C. endoplasmic reticulum.D. golgi body.

4. The function of the ribosomes can bedescribed as:A. storage of genetic information.B production of ATP.C. packaging of substances for secretion.D. manufacture of proteins.

5. Starch, glycogen and cellulose are all:A. proteins, composed of amino acids.B. nucleic acids, related to DNA & RNA.C. sugars, of the carbohydrate group.D. polymers of glucose.

6. The diagram shows acell surrounded by asolution which has a highconcentration of largemolecules.

You might expect:A. solute molecules to diffuse into the cell.B. water to diffuse into the cell.C. water to diffuse out of the cell.D. solute molecules to diffuse out of the cell.

7. A brick was smashed into smaller pieces witha hammer. It would be true to say that all thebrick pieces, when compared to the originalbrick, have:A. larger total volume.B. larger SA/Vol ratio.C. smaller total surface area.D. smaller SA/Vol ratio.

8. A food substance, which may be a mixture ofvarious organic chemicals, was tested with thefollowing results:Iodine solution gave a yellow, brown colour.Biuret reagent gave a purple colour.Benedict’s reagent resulted in a pale blue colour.

From these results you would conclude that thefood contains:A. protein, but no starch or sugar.B. starch, but no protein or sugar.C. sugar and protein, but no starch.D. sugar and starch, but no protein.

Longer Response QuestionsMark values given are suggestions only, and areto give you an idea of how detailed an answer isappropriate.

9. (3 marks) Compare the light microscope to the electronmicroscope in terms of how each forms animage, the magnification, and the resolution ofeach.

10. (2 marks) Using either the nucleus or mitochondrion asyour example, discuss the way that thestructure of the organelle relates to its function.

11. (4 marks) Using examples, discuss the difference between the“organic” & “inorganic” chemicals found in livingcells.

12 (2 marks) The cell membrane is described as being “semi-permeable”. Explain what this means.

13. (4 marks) Compare the processes of diffusion andosmosis, identifying what substances areinvolved and the direction of movement(compared to any “concentration gradient”)

14. (4 marks) Explain why all living cells have to be very small in size.

Worksheet 3 Practice Questions (Sections 1 & 2)




15

Photosynthesis in PlantsAll plants make their own food from the simple,low-energy raw materials water (H2O) andcarbon dioxide (CO2) using the energy ofsunlight, to make the high-energy sugar glucose(C6H12O6), with oxygen gas (O2) as a by-product.

This brief summary equation is very deceptive.Photosynthesis actually occurs as a complexseries of chemical steps inside the chloroplast.

There are 2 main stages, which take place indifferent parts of the chloroplast, as summarizedbelow.

Photosynthesis & Cellular RespirationYou will have noticed that these two vitalprocesses, when written as summary equations,are exact opposites.

What is really happening is ENERGY FLOW throughthe food chains of an ecosystem. Photosynthesiscaptures the energy of light and stores it in a highenergy food compound like glucose. Cellularrespiration releases that stored energy in the form ofATP which can power all cellular and life activities...growing, moving, keeping warm etc.

As you learned in Topic 1, in all ecosystems thereis a constant input and flow of energy via the foodchains, while the chemicals such as H2O, O2, andCO2 simply get re-cycled over and over.

The Most Important Process on EarthPhotosynthesis makes all the food on Earth, for allthe food chains. It also makes all the oxygen in theatmosphere for us animals to breathe.

For these two reasons, photosynthesis has to be themost important biological process on the planet.

3. NUTRITION IN PLANTS & ANIMALS

WATER + CARBON GLUCOSE + OXYGENDIOXIDE

6H22O + 6CO22 C66H1122O66 + 6O22

cchhlloorroopphhyyllll

lliigghhtt eenneerrggyy

lliigghhtt

PPhhaassee 11IInn tthhee ggrraannaa,,

cchhlloorroopphhyyllllaabbssoorrbbss lliigghhtteenneerrggyy aanndd uusseessiitt ttoo sspplliitt wwaatteerr

iinnttoo hhyyddrrooggeenn aannddooxxyyggeenn

PHOTOSYNTHESIS in the CHLOROPLAST

PPhhaassee 22IInn tthhee

ssttrroommaa,, aaccyyccllee ooff

rreeaaccttiioonnssbbuuiillddss

gglluuccoosseeffrroomm CCOO2aanndd tthhee

hhyyddrrooggeennffrroomm wwaatteerr

LLiigghhtt eenneerrggyy

MITOCHONDRIA - site ofcellular respiration

GLUCOSE+

OXYGEN

ATP

ggrreeeenn ppiiggmmeennttiinn cchhlloorrooppllaassttssooff ppllaanntt cceellllss

ttooaaiirr

hhiigghh-eenneerrggyy

ssuuggaarr ((ffoooodd))ffrroommaaiirr

ffrroommssooiill

CHLOROPLAST - siteof photosynthesis

Autotrophs & Heterotrophs An autotroph is an organism that makes its ownfood. All plants are autotrophic, making their ownfood by photosynthesis.

Any organism that cannot make its own food mustbe a heterotroph. All animals are heterotrophic, andso are the fungi and most bacteria.

A heterotrophic animal eats plants or other animalswhich have eaten plants, and so on according tothe food chain involved. CARBON

DIOXIDE+

WATER




16

What Happens to Glucose in a Plant?If photosynthesis only makes glucose, where do all theother biological chemicals in a plant come from?

Glucose is a monosaccharide sugar, a member of thecarbohydrate group. It is easy for a plant to convertglucose into other types of carbohydrate.

GLUCOSEmolecules

jjooiinneedd iinn ppaaiirrss

jjooiinneedd iinn 11000000’’ss

((ppoollyymmeerriissaattiioonn))

OOtthheerr ssuuggaarrss,, ssuucchh aass ssuuccrroossee

CELLULOSEfor building new

cell wallsSTARCH

for storage of food

In fact, plants convert glucose to STARCH sorapidly that the chloroplasts in a plant leaf

become packed with starch grains when it is photosynthesising.

THIS IS THE BASIS OF EXPERIMENTS YOU MAY HAVE DONE

Soil mineralsnniittrraattee,, ssuullffaattee eettcc

GLUCOSE Polymerisation

AAmmiinnooaacciiddss PROTEIN

cchheemmiiccaallccoonnvveerrssiioonn

Glucose can also be converted chemically intolipids... fats and oils, since they contain exactly thesame chemical elements (carbon, hydrogen &oxygen only - CHO).

GLUCOSE LIPIDS (oils)

Making proteins and nucleic acids is more difficult,since these contain additional chemical elements,especially nitrogen, phosphorus and sulfur.

This is where the “minerals” such as nitrate,phosphate and sulfate come in. Soil minerals areoften called “plant nutrients”, and a gardener maysay he/she is “feeding” the plants when applyingfertilizer, but these minerals are NOT food.

They are the essential ingredients needed so plantscan make proteins and DNA etc, from the realfood... glucose.

Experiments with PhotosynthesisThe classic experiment you have probably done, is to partly cover a leaf with

light-proof aluminium foil, and then expose it to light for several days. The aim is to prove that light is necessary for photosynthesis.

LLighht

Iodine testshows lots ofstarch here

No light,no starch

After several days, the leaf is decolourized (sothe test can be seen more easily) and thentested with IODINE solution.

Why Iodine? It detects STARCH, not glucose.

As explained above, the glucose produced byphotosynthesis is immediately converted tostarch. The iodine test is used because it is thetest for starch.

Sure enough, you probably found that any partof the leaf exposed to light turned black whensoaked in iodine, while parts under the foil didnot go black.

This proves that any part of a leaf allowed tophotosynthesise will build up a store of starchfrom the glucose it makes. The first product ofphotosynthesis is glucose, but it is rapidlyconverted to other things.

ExperimentalSet-uup

ResultAAluminnium foil




17

Plants Absorb Water through specialoutgrowths on the roots called “root hairs”.

Each root hair is part of one, very elongated cell.Root hairs help absorption of water by greatlyincreasing the surface area of the root in contactwith the soil.

MICROSCOPIC VIEW NEAR A ROOT TIPLONGITUDINAL TRANSVERSESECTION SECTION

XXYYLLEEMM TTUUBBEESS

ROOT HAIRSOOuuttggrroowwtthhss ffrroommeeppiiddeerrmmiiss cceellllss

PPhhllooeemmttuubbeess

EEppiiddeerrmmiiss llaayyeerr

The actual absorption of water is achieved byosmosis. The cell cytoplasm has a higher soluteconcentration than the water solution in the soil, sowater diffuses into the cell through the cell membraneof the root hair cells.

Once absorbed into the root hair cells, water diffusesfrom cell to cell towards the central xylem tubes whichcarry the water (and dissolved minerals) upwards tothe leaves. This upward flow is achieved by the plantconstantly allowing water vapour to evaporate fromeach leaf (“Transpiration”). This creates a “suction” atthe top of the xylem tube, rather like drinking througha straw.

Alongside the xylem tubes are the phloem tubeswhich carry food from the leaves to any part of theplant which cannot photosynthesize... especiallydown to the roots.

Together the xylem and phloem tubes form the“veins” in a plant. They not only carry substancesaround the plant, but are important as reinforcementand support structures.

Structure & Function... How Plants Get Water & Carbon DioxideIn order to photosynthesise, plants must collect water and carbon dioxide. In a land plant, water is

collected by the roots from the soil, and carbon dioxide is collected from the air into the leaves. Both roots and leaves require special structures to gather these vital chemicals.

The Importance of Surface AreaIt is generally true of many processes such as absorption and chemical reactions,

that the greater the surface area, the faster the rate of the process.

You may have done a simple experiment similar to this:-

The more finely divided a solid is, the greater its surface area, so the powder has more surface area than the lumps.

This experiment demonstrates the principle that things happen faster when more surface area is available for reaction or absorption.

Same quantity of same strength acid

Same quantityof solid calcium

carbonate oneach spoon

Lumps Powder

Both lumps andpowder react withacid in exactly thesame way, but youwould observe thatthe powder reacts

faster.




18

The Structure of the LeafA plant leaf is a factory for photosynthesis. A typical leaf is built so that every part of its design is suited

to the achievement of that one objective... making food. It is a classic case of Structure matches Function.

MICROSCOPICCROSS SECTION

THROUGH ALEAF

SURFACE VIEWOF A STOMATE

mmaaggnniiffiieeddaanndd

rroottaatteedd ttoossuurrffaaccee

vviieeww

The cuticle is a layer of clear,waxy material. It allows lightthrough, but is waterproof toprevent excessive water loss. The epidermis

layer of cells istransparent like a

window, to letlight through to

the cellsunderneath.

The Palisade Layer ofcells are tightly packed in

an orderly rowimmediately under the topepidermis where there ismaximum light. Each cell

contains manychloroplasts. This is the

“engine room” forphotosynthesis.

The Spongy Layer hasvery loosely packed

cells, with lots ofspaces around them.

This allows gases (CO2& O2) and water to

easily move around bydiffusion.

The lower leaf surface has many openings, called“stomates”. These allow:

• water to evaporate from the leaf (Transpiration).This ensures that water and minerals continue to be“sucked up” from the roots.

• CO2 to diffuse into the leaf for photosynthesis.

• O2 to diffuse out of the leaf into the air.A magnified surface view of a stomate is shown.

Veins run throughouteach leaf. The xylem tubesbring water and minerals

from the roots and releasethem into the spongy layer.From there, some diffuses

into the cells forphotosynthesis, while the

rest evaporates through thestomates.

There are phloem tubes aswell, which collect the food

manufactured in the leafcells and carry it away to

feed other parts of theplant, such as roots, stemand flowers which might

not be able tophotosynthesise.

Veins also act asreinforcing, helping to keepthe flimsy leaf deployed to

catch maximum light.

PPoorreeooppeenniinngg

A leaf is generally broad, flat andthin. This gives it maximum

surface area for absorbing lightand carbon dioxide from the air. A leaf is thin enough that light

penetrates to reach each layer ofcells within, for maximum

photosynthesis.

The “veins” contain xylem tubes forcarrying water and minerals up from

the roots, and phloem tubes forcarrying manufactured food away.

Being specially reinforced withtough “lignin”, the veins also

support the flimsy leaf, and keep itin shape and positioned to catch

maximum light.

Each stomate pore is an openingformed between two special “guard

cells”. These cells can change shapeto open the pore, or close it up to

minimize water loss in dryconditions. The guard cells changeshape by using osmosis to either

pump-up full of water (pore open), ordeflate and shrivel (pore closed).




19

Nutrition in AnimalsAnimals are Heterotrophs.

They must eat energy-rich food made by other organisms, either plants or other animals.

The food an animal eats is composed largely of complex carbohydrates, proteins and fats which must be digested before being absorbed intothe body and used by the cells.

Digestion involves chemically breaking large molecules down into smaller units which canbe carried around the body and transportedacross cell membranes.

EENNZZYYMMEEStarch

molecule

Sugarmolecules

Proteinmolecule

EENNZZYYMMEE

Amino acidmolecules

HUMAN DIGESTIVE SYSTEM

Chewing the food begins thedigestion process.

Chewing breaks food intosmaller pieces with greatersurface area, so digestive

enzymes can attack it faster.

Salivary Glands. An enzyme in saliva beginsdigesting starch.

Liver receives and

processes digestednutrients after theyare absorbed into

blood stream.

Gall bladder adds bile todissolve fats so enzymes

can digest them.

Small Intestinecompletes digestion with acocktail of enzymes, thenabsorbs nutrients into the

blood stream.Inside, it has many folds or“villi” which increase surface

area for absorption.

Caecum & Appendixhave no special functions

in humans

Oesophaguscarries food to the stomach.

Stomachchurns food with acid.Enzymes digestproteins in food

Large Intestineabsorbs water, vitamins &minerals into blood stream.

Rectum stores undigestedwastes (faeces) for laterelimination.

Pancreasadds a cocktail ofenzymes to futherdigest food




20

Digestion in HerbivoresPlant-eaters face a problem... a lot of plant materialhas a low nutrient value and contains a lot offibrous matter which is difficult to digest. The fibreis mostly the plant cell walls, made of cellulose... apolymer of glucose, but animals lack the necessarydigestive enzymes to break the cellulose down.

Herbivores usually have:-• flat, grinding teeth to chew the food thoroughly to

increase the surface area exposed to enzymes.• relatively long intestines and caecum, for more surface area and longer time available fordigestion.

• bacteria living in their gut which have enzymes todigest cellulose.

This is an example of “mutualism”.

LLoonngg LLaarrggee IInntteessttiinnee

HHuuggee CCaaeeccuumm

SSttoommaacchh

LLoonngg SSmmaallllIInntteessttiinnee

GGrriinnddiinnggtteeeetthh

Digestion in CarnivoresFlesh eaters don’t need such huge digestivesystems. Their food is much more concentratedin its nutritional value, and relatively easy todigest.

Carnivores usually have:-• sharp, tearing teeth tocut flesh into chunks forswallowing... chewing isnot so important.

• relatively shortintestines.

• a highly elastic stomach,which allows them toswallow a large meal. The stomach acid andenzymes are vital fordigesting their high proteinmeat diet.

Different Animals Have Different SystemsThe digestive systems of different animals are often quite similar, but certainly not identical.

Once again, the principle of “structure matches function” can be noticed.

SShhoorrtteerriinntteessttiinneess

SSttoommaacchhmmoorree

iimmppoorrttaanntt

Digestion in a Nectar FeederSome animals eat a diet that requires very little digestion at all.

Many birds (eg honey-eaters, humming birds) and insects (eg butterflies) feed largely on the sugary nectar of flowers.

Sugar does not require any digestion at all, so their digestive system can be very short and simple.

A short-lived butterfly only needs nectar for the energy its sugar supplies, but a bird needs more nutrients. Most eat the plant pollen which is rich in

protein and oil. Therefore, their short little digestive system does need to do some work, apart from simply absorbing sugar.

Nectar & Pollen feeding lorikeet

TTeeaarriinnggtteeeetthh




21

Worksheet 4 Nutrition in PlantsFill in the blanks.

(a)....................................... (e.g. plants) areorganisms that can make their own food,while (b)................................ (such asanimals) cannot.

The process of photosynthesis can besummarized as

(c)................. + (d)....................................

(e).................. + (f).....................

Photosynthesis occurs in the(g)................................ (organelle) in plantcells. The green pigment (h)....................absorbs (i)...................... energy for theprocess. This energy is stored aschemical energy in the(j)................................. molecules produced.

Thousands of glucose molecules can bejoined together by the process of(k)..................... to form (l)..........................(used for storage) or cellulose which isused to build (m).....................................

Glucose can also be chemically convertedinto (n).................................. To convertsugar to amino acids, the plant needs asupply of (o)...........................................

Amino acids can then be joinedtogether to form (p)..................................

The structures mainly responsible forabsorbing water into a plant are the(q)....................................... which areoutgrowths of root cells and greatlyincrease the (r)........................................of the roots. Water is absorbed by theprocess of (s)............................................then transported up to the leavesthrough (t).................................. tubes.

In a leaf, there are many examples of“structure matching function”, such as:• The shape of the leaf gives maximumsurface area for (u)....................................

• The (v)................................................layer of cells, packed together & full ofchloroplasts for maximum photosynthesis.

• The “spongy layer” of loosely packedcells to allow (w)........................................

• The (x)..................................... whichcan open and close and allow water toevaporate (called (y)............................)and to let the gas (z)..................................in for photosynthesis.

Worksheet 5 Nutrition in AnimalsFill in the blanks

Animals have to digest the food theyeat. This is carried out by digestive(a)............................ which, for example,break starch into (b)........................... andproteins into (c)........................................

There are 4 organs in the mammaldigestive system that produce digestiveenzymes. Name them all.(d)........................., ........................................................... and ...............................

Digestion begins with chewing foodwhich increases the (e).............................of the food, so enzymes can attack itfaster.

Digested nutrients are absorbed into theblood stream from the (f).........................,then carried in the blood to the(g)........................... for processing.

Herbivorous animals usually have:• (h)...................... teeth to chew thoroughly• relatively (i)........... intestines and caecum• mutualistic (j).................... living in theirgut to help them digest (k)...........................which is a major part of their diet.

Compared to them, carnivores usuallyhave (l).......................... teeth andrelatively (m)............................ intestines

Nectar feeders, such as (n).......................have digestive systems which are very(o).......................... and .........................



22


Multiple Choice1. The chemical raw materials needed forphotosynthesis are:A. glucose and oxygen.B. water and carbon dioxide.C. carbon dioxide and oxygen.D. water and glucose.

2. The chemical “ATP” is best described as:A. the carrier of genetic information.B. the product of cellular respiration.C. the absorber of light for photosynthesis.D. a waste product from the mitochondria.

The following sketch shows a cross-sectionthrough a leaf. Use the diagram for Q. 3 & 4

3. A structural feature which helps thefunctioning of the leaf is that the cells at “P”:A. are transparentB. are loosely packedC. contain many chloroplastsD. open up to let gases in/out

4. The “guard cells” are labeledA. Q B. R C. S D. T

5. Soil minerals such as nitrates, phosphates andsulfates are essential to a plant for which purpose?A. To provide energy.B. To make starch from glucose.C. As raw materials for photosynthesis.D. To make proteins from glucose.

6. In a mammalian digestive system, the mainchemical digestion in the stomach involves thebreakdown of:A. starch. B. protein.C. lipids.D. sugars.

7. An animal with large, flat, grinding teeth and avery large caecum (a blind “pocket” of theintestine) probably eats mainly:A. nectar, pollen and flowers.B. the flesh of other animals.C. plant leaves and grass.D. fish & other seafood.

Longer Response QuestionsMark values given are suggestions only, and areto give you an idea of how detailed an answer isappropriate. Answer in the spaces provided.

8. (2 marks) Differentiate between “autotrophs” & “heterotrophs”,including examples in your answer.

9. (5 marks) a) Summarize the process of photosynthesis bya word equation, including the energy source.

b) Give two reasons why photosynthesis can beconsidered the most important biologicalprocess on Earth.

10. ( 5 marks) In experiments on photosynthesis, the presenceof starch in leaves is often taken as proof thatphotosynthesis has taken place.a) Explain why it is starch, not glucose, that theleaves are tested for.

b) Outline the method of testing for starch in aleaf, including any preliminary treatment(s).

11. (4 marks) Discuss the relationship between structure andfunction shown by the leaf cell layers known asthe “palisade layer” & the “spongy layer”.

12. (3 marks) Briefly outline how the length and complexity of ananimal’s digestive system is related to its diet.Refer to 3 different types of diets in your answer.

Worksheet 6 Practice Questions (Section 3)

P

Q

R

S

T




23

Organisms Need What Cells NeedEvery living cell, plant or animal, has certainrequirements:-

A single-celled organism exchanges these chemicalswith the environment directly through its cellmembrane. However, in all multicellular organismsmost of the cells are located deep within the body.There have to be body systems to:-

• absorb nutrients, water and oxygen• excrete wastes• transport all these chemicals between the cells and the environment.

In animals the body systems involved are:Digestive system absorbs nutrients and water.Respiratory system (e.g. lungs) exchanges gases,absorbing oxygen, and excreting carbon dioxide.Excretory system (kidneys) removes other wastessuch as urea.Circulatory system (blood, heart, veins etc)transports all these things around the body.

Plants also have systems for exchanging gases,and for transporting substances around theirbodies.

Requirements for Gas ExchangePlant or animal, large or small, all organisms needto exchange gases with their environment.Efficient gas exchange requires:-

• a large surface areain contact with the environment.

• a moist gas exchange membranebecause the gases must dissolve in water beforepassing through the membrane by diffusion.

• close contact with the blood supply (or other transport system) to carry gasesbetween cells and the gas exchange organs.

Gas Exchange in AnimalsThere are many ways that animals carry out gasexchange. This section will compare four differentsystems... mammal, frog, fish and insect.

Lungs in a MammalUsing the human as a typical example:

The lung is not justa hollow space like a balloon. If it was, the surface area forgas exchange would be about the size of thispage. By dividing into millions of alveoli, the totalsurface area inside your lungs is about the samesize as a tennis court!

The inside surface is always moist, for gases todissolve and diffuse, and each alveolus is inintimate contact with a blood capillary totransport the gases to and from the body cells.

The requirements for efficient gasexchange have been met.

4. GAS EXCHANGE & INTERNAL TRANSPORT

FOOD inWATER in

OXYGEN in

WASTE PRODUCTS such as CO22 must be excreted

AAIIRR fflloowwssiinn aanndd oouutt

Bloodcapillary

BBlloooodd ffllooww

O22

CO22

Bronchiole

Trachea(Windpipe)

Each bronchussub-ddivides

intoBronchioles

Lungsare not

hollow, butsponge-llike

Bronchi(sing: bronchus)

carry air to each lungEEaacchh bbrroonncchhiioollee

eennddss iinn aa cclluusstteerrooff ttiinnyy aaiirr ssaaccss......tthhee Alveoli

Each Alveolus has a walljust 1 cell thick, and the

internal surface is kept moist

HUMANRESPIRATORY

SYSTEM




24

Gas Exchange in a FrogAmphibians hatch from theiregg as “tadpoles” which livein water and breathe with gills.Later they undergometamorphosis and develop into the adult formwhich breathes with lungs.

However, a frog’s lungs are much simpler than amammal’s, and don’t have as many alveoli.

Doesn’t this mean less surface area and lessefficiency? Yes, but a “cold-blooded” frog doesn’tneed to carry out cellular respiration just to makebody heat the way mammals do. So the need for O2intake is a lot less. Also, the frog doesn’t just dogas exchange in its lungs...

The frog makes up for its inefficient lungs bycarrying out gas exchange through other bodysurfaces which are kept moist and are lined withblood vessels... its mouth and throat cavity and theskin all over its body.

Gas Exchange in a FishLand-dwelling, air-breathing animals always musthave their gas exchange organs inside their bodies sothe moist membranes won’t dry out. In water this can’thappen, so a fish’s gills are exposed to the waterenvironment, but shielded by a tough “gill cover” toprotect the delicate breathing organs.

The gills are a series of feather-like plates aroundwhich the water flows. Each gill plate consists ofthousands of tiny “filaments” each one a thin leaf-shaped structure packed with blood capillaries.

Gills have to be highly efficient, because rememberfrom Topic 1, that the level of oxygen dissolved inaquatic environments is much lower than theconcentration in air.

FROG RESPIRATORY SYSTEM

Simple Lung Mouth andthroat cavityare moist &lined with

blood vessels

Moist Skin also acts as a gas exchange surface

FISH BREATHE WITH GILLS

WWaatteerriinn

Gillsuunnddeerr ggiillll ccoovveerr

GGaasseess aarreeddiissssoollvveedd iinntthhee wwaatteerr

WWAATTEERR FFLLOOWWSSAACCRROOSSSS && BBEETTWWEEEENN

FFIILLAAMMEENNTTSS

WWAATTEERR FFLLOOWW

Bloodflow

GILL FILAMENTS

BLOOD FLOW IN CAPILLARIES

WWaatteerr oouutt

Insects don’t have lungs or gills. Along the sides oftheir bodies is a series of holes called spiracles. Eachspiracle allows air to move into a network of tubes(“trachea”) which infiltrate their whole body.

Spiracles

TracheaThe trachea tubes are moist inside

for gas exchange. Gases diffusedirectly to the body cells, which are

never far from a trachea tube.The network of tubes increases the

surface area for gas exchange.

This system is quite efficient in a small animal, butrapidly becomes inadequate as the animal growslarger, because the Surface Area to Volume Ratiogets smaller.

That’s why there’s no such thing as a really big bug!Hollywood fantasies cannot actually happen.

Gas Exchange in an Insect

Study each system again... mammal, frog, insect, fishand note of how each system achieves the threeessential features of any gas exchange system...

• LARGE SURFACE AREA

• MOIST MEMBRANE SURFACE for diffusion

• CLOSE CONTACT WITH BLOOD STREAM or body cells.



25

Internal Transport in AnimalsOnce nutrients and gases have been absorbed intothe body, they need to be transported to every bodycell. In animals this is the job of the CirculatorySystem, consisting of the heart, blood vessels andthe blood itself.

Once again, different types of animals have allsorts of variations, but in this section only a broadcomparison between two general types of systemwill be made.

Closed Circulation SystemsAll vertebrate animals (fish, amphibians, reptiles,birds and mammals) have a blood system that is“closed”... the blood is always flowing inside ablood vessel, pumped around by the heart.

This system is highly efficient because the bloodcan be kept flowing within the vessels,guaranteeing a steady flow of nutrients, gases andwastes between body cells and the outsideenvironment. This efficiency allows vertebrates togrow very large and still function perfectly despitethe poor SA/Vol ratio of a large body.

Be aware that fish, amphibians and most reptilesdo not have a system quite the same as a mammal,but in all cases the system is “closed”.

Open Circulation SystemsInvertebrate animals (including insects, worms& snails) have much simpler circulatory systemsin which the “blood” (or a fluid doing the samejob) does not always stay inside a blood vessel.

The “open” system is not very efficient, becausethe blood is not forced to keep flowing throughblood vessels as in a closed system.

However, in a small insect, with its separate gasexchange system which is not dependent onblood flow, this is obviously quite adequate...after all, insects are the most numerous animalson the planet!


CLOSED CIRCULATION IN A MAMMALSchematic Diagram

Capillarynetworkin Lungs

Alveoli (airsacs)

in lungs

HEARTpumps blood

Vein

s

Arte

ries

Vein

Body cellsreceive O22 & nutrients,

and get rid of CO22 & other wastes

OPEN CIRCULATION IN AN INSECTSchematic diagram

Heartpumps“blood”

fluid

Arteries

Veins

Circulatory fluidflows out of

blood vessels

Fluid slowly collects back into veins. Wastes (but not CO22) are taken away for

excretion, and blood returns to the heart.

Artery

Capillary network in body

CCOO2 OO2

Blood fluid flowsdirectly among

body cells




26

Xylem tubes carry water and dissolvedminerals from the roots to the leaves.

The upward movement of water in xylem tubeshappens without any effort by the plant... it is“passive transport”. The evaporation of water fromthe leaves through the stomates, (“Transpiration”)causes a “suction” effect at the top of each xylemtube. This draws more water from the roots.

Rate of TranspirationYou may have done experiments on transpirationto measure it, and the factors which affect its rate.A common way to do this is with a “potometer”:-

Hollow, deadcells, joinedend-tto-eend

forming atube

Cell wallsre-iinforcedwith ringsand spirals

of lignin

Typically it is found that the rate of transpiration isincreased by higher temperatures, air flow (wind), lowhumidity and increased light. (The effect of light is because when lit, most plantsopen their stomates to get CO2 in for photosynthesis.The open stomates then allow more transpiration.)

POTOMETER METHOD FORMEASURING TRANSPIRATION

Fresh plantshoots

RRuulleerr mmeeaassuurreess mmoovveemmeenntt ooff aaiirrbbuubbbbllee iinn ttuubbee

GGllaassss ttuubbee ffiilllleedd wwiitthh wwaatteerr..AAss TTrraannssppiirraattiioonn ooccccuurrss ffrroomm tthhee lleeaavveess aannddssuucckkss wwaatteerr uupp ffrroomm bbeellooww,, aann aaiirr bbuubbbbllee iiss

ssuucckkeedd iinn aatt tthhee eenndd ooff tthhee ttuubbee.. AA rruulleerrggiivveess aa ssccaallee ttoo mmeeaassuurree rraatteess ooff

ttrraannssppiirraattiioonn uunnddeerr ddiiffffeerreenntt ccoonnddiittiioonnss..

RRuubbbbeerr ttuubbee ((ffiilllleedd wwiitthh wwaatteerr))

ccoonnnneeccttss ggllaassss ttuubbeettoo lliivvee ppllaanntt sshhoooott

Internal Transport in PlantsPlants have two separate systems for transporting substances inside their bodies...

PhloemPlants have a separate set of tubes for transportingsugars and other food nutrients; the phloem tubes.

While the xylem tubes are formed from dead cells, thephloem are living cells joined end-to-end. The ends ofeach cell are perforated (“sieve plates”) so each cell isopen into the next so they form a continuous tube.

It is an “active transport”operation, meaning that theplant has to use energy tocause the material to flow.

PHLOEM CELLaalliivvee aanndd ffiilllleedd wwiitthh

ccyyttooppllaassmm..

MMoovveemmeenntt ooffccyyttooppllaassmm ccaarrrriieessssuuggaarrss tthhrroouugghh

eeaacchh cceellll

SSiieevvee ppllaatteebbeettwweeeenn cceellllss

“Companioncell”

hhaass mmaannyymmiittoocchhoonnddrriiaa ttoopprroovviiddee AATTPP ttootthhee pphhllooeemm cceellll

ssuuggaarrss aarree aaccttiivveellyyttrraannssppoorrtteedd iinn tthheeccyyttooppllaassmm ooff tthhee

cceellllss

A “companion cell” beside the phloem cellsupplies ATP from cellular respiration to power theactive transport in the phloem tube.

While the xylem is a one-way flow system, thephloem system can carry food (especially sugars)in either direction.

If a lot of photosynthesis is occurring, the phloemwill carry sugar to storage sites in roots or stem.

If photosynthesis is not possible for an extendedtime, then the phloem will carry sugars back fromthe storage sites to feed the leaf cells, or supply agrowing flower or fruit.

The movement of food via the phloem is called“Translocation”.

TThhee ffllooww oofflliiqquuiidd iiss ccaauusseeddbbyy ddiiffffeerreenncceess iinn

oossmmoottiiccpprreessssuurree




27

The Use of Radio-isotopesto Study Transport Systems

The atoms of each chemical element are not allexactly the same. They have the same number ofprotons & electrons (that’s what makes themthat element), but the number of neutrons in theatom may vary. Such atoms of the sameelement, but with a different number ofneutrons, are called “isotopes”. Some isotopesare “radioactive” and give off nuclearradiations... hence “radio-isotopes”.

The radiation they give off can be detected byphotographic paper or special instruments suchas the “Geiger counter”. If a radio-isotope isintroduced into a plant or animal, its transportthrough the body can be followed by monitoringthe radiation the isotope emits.

This “tracer” technique is one of the moreimportant methods used to study the movementof substances in living things. This is how a lotof our knowledge of transport systems has beendiscovered.

For example:If a leaf is exposed to CO2 containing “carbon-14”(a radio-active isotope of carbon):

Next,radiation is found insugars inphloem tubes

Later, it’s here

Later still, theradiation is

detected in starchstored here

From studies likethis we learn the

details of thechemistry and

transport systemsinside living

things

Soon, radiation isdetected in starch

grains in leafcells.

Radioactive CO22 absorbed by leaf

Gas Exchange in PlantsThe structure and functioning of the leafstomates was covered earlier.

What about other parts of a plant?

Lenticelsare simple structures on the stems and trucks ofplants which allow gas exchange to the cells bysimple diffusion from the air.

Root Hairs were covered earlier in connectionwith water absorption.

Because they increase the surface area of theroots, root hairs are important for gas exchangeas well as water absorption. Oxygen in soilspaces, or dissolved in soil water simplydiffuses into the root hair cells, and spreads toother root cells by further diffusion.

Tightly packedstem cells

Surface cells

Lenticel opening

Loosely packedcells allow gases

to diffuse in and out




28

Fill in the blank spaces & diagram labels.

The 3 requirements for an efficient GasExchange system are:• large (a)...................................................

• gas exchange membrane which is kept (b)..............................

• close contact with (c)....................... ......

In any gas exchange system, the gasesmove across the membrane by theprocess of (d)...........................................

Compared to a mammal’s lung, the lungof a frog is (i)......................... Frogsexchange gases through their(j)......................... and ...............................as well as lungs.

Insects have a series of holes called(k).................................. along their bodywhich lead into a network of tubescalled (l)................................ This worksOK for small insects, but means noinsect can ever be really large becauseits (m)........................................... ratiowould be too small for sufficient gasexchange.

In a fish’s (n)........... there are thousandsof leaf-shaped (o)..................... aroundwhich water flows. In each filament areblood capillaries in which blood alwaysflows (p)............................ to the waterflow. This “(q)......................................current” flow is much more efficient.

In a “(r).................................... circulatorysystem” the blood is always insideblood vessels, and kept circulating bythe pumping of the(s)......................................

(t)......................................... animals have“open circulatory systems” in which theblood leaves the blood vessels andflows directly in contact with the bodycells.

(e).............................

(f)............................

(g).......................................

(h)........................(microscopicair sacs)

Fill in the blanks

Gases exchange in a plant occursthrough the (a).................................... ofthe leaves, and via the(b).............................. of stems, and the(c)............................. in the roots.

Xylem tubes carry (d)................................and ........................ from (e).......................to (f)..............................

The evaporation of water from theleaves is called (g)....................................

It is increased by factors such as(h)........................... and (i)........................

Food nutrients are carried by the(j)......................................... tubes. Thistransport is called (k)................................and is considered “active” transportbecause (l)...............................................................................In contrast, xylem transport is(m)..................................................

Worksheet 7 Gas Exchange & Transport in Animals

Worksheet 8 Gas Exchange & Transport in Plants



29


Multiple Choice1. Which of the following is NOT an essentialfeature of a gas exchange system?A. Close contact with the blood supply.B. Large surface area.C. Strong protective shielding.D. Moist membrane.

2. An animal’s respiratory system consists of aseries of holes along the body which allow air tocirculate into a network of tiny tubes throughoutthe tissues. This animal is probably a/an:A. insect.B. frog.C. fish.D. reptile.

3. A plant would probably show the lowest rateof transpiration under conditions of:A. hot & windy.B. bright light & low humidity.C. hot & bright light.D. high humidity & cool.

4. Which of the following correctly gives a structuralfeature and a functional feature of xylem tubes?A. living cells which transport waterB. reinforced with lignin, carry out passive transportC. dead, hollow cells, carrying food nutrientsD. cells filled with cytoplasm, carrying out activetransport


5. (6 marks) Contrast the processes of Transpiration andTranslocation in a plant, includinga) the substances transported

b) the plant tissues involved

c) the basic mechanism of transport involved.

6.(3 marks) Explain the roles of the respiratory, excretoryand circulatory systems of a mammal, and anyconnection between them.

7. (4 marks) One of the main features of any respiratorysystem is a large surface area for gas exchange. Outline how a large surface is achieved in a a) mammal

b) frog

c) fish

d) insect

8. (4 marks) Using simple schematic diagrams, contrast thecirculatory systems of vertebrate andinvertebrate animals. Answer on reverse.

9. (4 marks) a) Identify THREE structures in a plant which areinvolved in gas exchange.

b) Choose ONE of the structures listed in part (a)and describe one feature of it which aids gasexchange in the plant.

10. (4 marks) Outline the way in which technology, such asradio-isotope “tracing” is used to study the pathof elements through a living plant or animal.

Worksheet 9 Practice Questions (Section 4)




30

The Need For Cell DivisionSingle-celled organisms reproduce by simplydividing in two.

In a multicellular plant or animal cell division is vitalfor growth. Remember that individual cells cannotgrow large because as they do, their SA/Vol ratiogets smaller, and they cannot get materials in andout through their cell membrane fast enough tosurvive. So, the only way to grow larger is toproduce many small cells.

Cell division is also used to replace damaged orworn out cells in the body. For example, yourbody is constantly producing new blood cells toreplace those that wear out.

The Process of Cell DivisionCell division occurs as a sequence of steps or“phases” as summarized by this schematic diagram.

Steps ...more information

Mitosis Through the MicroscopeYou may have done a laboratory practical in which youused a microscope to examine a prepared slide ofcells undergoing cell division. Commonly the root tipof a plant seedling is viewed. This sketch showsroughly what the cells may look like...

5. CELL DIVISION FOR GROWTH & REPAIR

Once separated, eachset of chromosomesforms a new nucleus

Finally, the cellmembrane grows

to divide the cell in2 parts, with a

share of cytoplasmand organelles in

each

GGeenneettiicc iinnffoorrmmaattiioonn iissssttoorreedd iinn tthhee cceellllnnuucclleeuuss,, aass DDNNAA..

TThhee DDNNAA iiss ccoonnttaaiinneeddiinn tthhrreeaadd-lliikkee

““cchhrroommoossoommeess”” wwhhiicchhaarree nnoott nnoorrmmaallllyy

vviissiibbllee..

TThhee nnuucclleeaarr mmeemmbbrraanneeddiissssoollvveess ssoo

cchhrroommoossoommeess ccaann mmoovveerriigghhtt aaccrroossss tthhee cceellll..TThheeyy aarree mmoovveedd bbyytthhrreeaaddss ccaalllleedd ““tthhee

ssppiinnddllee”” wwhhiicchh aacctt lliikkeeffiisshhiinngg lliinneess,, rreeeelliinngg

tthheemm ttoo ooppppoossiittee ssiiddeessooff tthhee cceellll

THIS

IS M

ITO

SIS.

.. TH

E D

IVIS

ION

OF

THE

CELL

NUC

LEUS

This final divisionis called

“CYTOKINESIS”

MMoosstt cceellllss llooookk lliikkee tthhiiss oonnee..NNoo cchhrroommoossoommeess vviissiibbllee,,bbuutt DDNNAA iiss bbeeiinngg ccooppiieeddrreeaaddyy ffoorr mmiittoossiiss ttoo ssttaarrtt..

TThheessee hhaavvee jjuussttffiinniisshheedd ddiivviiddiinngg

tthhee nnuucclleeuuss..

TThheessee hhaavvee jjuussttffiinniisshheedd

CCyyttookkiinneessiiss..

CChhrroommoossoommeessjjuusstt bbeeccoommiinngg

vviissiibbllee.. MMiittoossiiss iiss

uunnddeerr wwaayy..

These 3 lower diagrams show how mitosis isoften drawn in textbooks, in a stylized way.If you need to sketch them, do it like this for

greater clarity

CChhrroommoossoommeess bbeeiinnggppuulllleedd aappaarrtt..

CChhrroommoossoommeess lliinneedduupp iinn mmiiddddllee ooff cceellll..

CChhrroommoossoommeess bbeeccoommeevviissiibbllee aafftteerr ccooppyyiinngg..

Original “parent”cell makes a copy

of its geneticinformation

CChhrroommoossoommeesshhaavvee lliinneedd uuppiinn tthhee mmiiddddllee

ooff tthhee cceellll..

CChhrroommoossoommeessbbeeiinngg ppuulllleeddaappaarrtt iinnttoo 22

iiddeennttiiccaallggrroouuppss..

The chromosomescondense together

and becomevisible.

They line up in themiddle of the cell,then separate into2 identical groups



31

The Results of Cell Division• One parent cell divides to form 2 “daughter” cells.

• Each daughter cell is genetically identical to theother, and to the parent cell. This is because theoriginal DNA was first duplicated (“replicated”) thendivided into twoduplicate sets by mitosis.

• The daughter cells are not necessarily identical insize, but each gets a share of cytoplasm, mitochondria, ribosomes and all other organelles.

• Each daughter cell can then make more organelles, and grow in size, until it is full size.Each may then undergo cell division again. Thisendless repetition of cell growth and cell division iscalled the “cell cycle”.

You began as a single cell. It divided by mitosis, thendivided again and again, until today you are a complexorganism of about 300 billion cells. Each of your cellsis genetically identical to every other, and to thatoriginal cell you came from.

Even when you have finished growing, mitosis willcontinue in many parts of your body:

• skin, to replace the layers that constantly flake off.• hair and finger-nails, which grow all your life.• bone marrow, where blood cells are constantlybeing produced to replace those that wear out.

• anywhere else where injury or cell death requiresreplacement.

Mitosis in Other OrganismsA human baby is more or less the same shapeas an adult, and simply grows bigger,proportionally all over, to become an adult. Inother organisms though, cell division occursonly in certain parts of the body, and growth isnot proportional.

Plantsgrow only at certain places known as“meristems”. These are located:

• at the root tip.• at the “buds” where shoots & flowers grow.• in the cambium layer, between xylem & phloem.(cambium growth is how the stem/trunk gets larger)

Insectsgrow differently in two distinct stages.

Most insects hatch from their egg as a “larva”...a caterpillar, grub or maggot. The larva does notundergo cell division at all, but grows rapidly byincreasing the size of each cell. (within the limitsimposed by the SA/Vol ratio, of course)

Next, the insect larva undergoes metamorphosisand totally changes its body plan. This isachieved by special “disks” of cells which beginmitosis in particular directions, each forming adifferent body part such as a wing, leg or vein.These “disks” correspond to the meristems of aplant, as special sites of mitosis.


A Final Note...The main store of genetic material is the DNA in the nucleus, but that’s not the only place in a cell whereDNA is found. DNA is also located in the mitochondria, and in chloroplasts in plant cells. Theseorganelles are able to reproduce themselves (at least in part) in mini-versions of cell division.

This occurrence of DNA in these two important organelles (both concerned with food & energy,and its flow in ecosystems) will be dealt with in a later topic. The evidence points to a veryinteresting evolutionary origin for these organelles...

Nuclear DNA

Mitochondrial DNA Chloroplast DNA




Fill in the blank spaces

In a multicellular organism, cell division isnecessary for (a).................................. and toreplace damaged or worn out cells.

Mitosis refers to the division of the(b)............................., while the division ofcytoplasm into 2 cells is called(c)............................................................

Before mitosis becomes visible in a cell thegenetic information (d).............................. ...........

The genetic information is contained in thechemical (e).................... which is built intothread-like structures called (f).............................

The visible sequence of mitosis is:• chromosomes thicken, become visible, and thenuclear membrane (g)....................

• chromosomes (h).................................... in themiddle of the cell

• chromosomes move to opposite ends of thecell, pulled by the threads of the(i)............................................

32

• Each group of chromosomes forms a new(j)........................................................ thencytokinesis divides the cell itself.

The results of cell division include that thedaughter cells are genetically(k)......................................, and identical to the(l).......................... cell.

Apart from the nucleus, 2 other organellescontain DNA. These are the (m)..........................and .....................................

Sites of mitosis in a plant are called“(n)................... located at (o)........................, and(p)................................ as well as the cambiumlayer in the stem.

Most insects hatch from their egg as aq)................. which grows by cell r)......................,without cell s).............................. Later, theyundergo t)......................................... in which theirbody tissues totally u)..........................................and are re-built to form the totally different adult.During this process, cell division occurs only inspecial “v).........................................” of cells.

Worksheet 10 Cell Division

Worksheet 11 Practice Questions (Section 5)Multiple Choice

1. The sketch shows some plant cells which areundergoing cell division.

The correct sequence of cell division is shown by thecells A. SPQTRB. RSPTQC. RQPTSD. PQTSR

P

Q

R

ST


2. (6 marks) Describe the sequence of steps that occur in theprocesses of mitosis & cytokinesis.

3. (4 marks) a) Identify the parts of a plant where cell divisionoccurs.

b) Contrast the general pattern of growth of aplant with that of a vertebrate animal such as amammal.




33

CONCEPT DIAGRAM (“Mind Map”) OF TOPICSome students find that memorising the OUTLINE of a topic

helps them learn and remember the concepts and important facts. Practise on this blank version.

PATTERNSin

NATURE



34

Answer SectionWorksheet 1 Cell Structurea) all living things.... b) ...pre-existing cellsc) microscopes d) resolutione) electron f) magnificationg) Robert Hooke h) cytoplasmi) nucleus j) chloroplastk) cell wall l) cell membranem) vacuolen) cell wall & (o) chloroplast(p)-(t) (any order) golgi body, endoplasmicreticulum, mitochondria, ribosomes, lysosomes(u) controls substances going in/out of cellv) Endoplasmic reticulumw) packaging substances for storage or secretionx) mitochondria y) chloroplastz) strength/ rigidity/ protection on outside ofplant cell

Worksheet 2 Chem & Membranea) inorganic b) carbonc) proteins d) membranee) energy storage compoundsf) carbohydratesg) C6H12O6 h) photosynthesisi) cellular respiration j) DNAk) sugar (glucose) l) Biuret reagentm)yellow/brown n) black/dark blueo) phospholipid p) permeableq) high(er) r) lowers) water t) gradientu) passive v) energy or ATPw) Surface area / Volume x) volumey) cell membrane z) surface areaaa) many ab) large

Worksheet 31. C 2. A 3. B 4. D 5. D 6. B 7. B 8. A

9. The light ‘scope forms images by focusinglight beams with glass lenses. Electron ‘scopesfocus beams of electrons using magnetic fields.Light scopes achieve magnifications around500X and resolution of about 0.2 um. Electronscopes are 500-1,000 times better in eachdepartment.

10. Nucleus- membrane has pores to allow RNAmessengers to go out into the cell.ORMitochondrion- inner membrane is highlyfolded for more surface area. The enzymes ofcellular respiration are arranged on thesemembranes for greater efficiency.


11. Organic chemicals are mainly complexmolecules, often polymers, based on theelement carbon. e.g. carbohydrates, proteins, lipids & nucleic acids.Inorganic chemicals in living cells are small,simple molecules or mineral ions e.g. water,oxygen, nitrate & chloride ions.

12. Semi-permeable means that somechemicals can diffuse through it easily, whileothers cannot get through .

13. Diffusion is the movement of any solute,solvent or gas along the concentrationgradient.Osmosis is the diffusion of WATER, against theconcentration gradient, through a semi-permeable membrane.

14. As any object gets larger, its SA/Vol ratiogets smaller. A cell needs nutrients, oxygen, etcin proportion to its volume, but must get thesesubstances in through its cell membrane, thesize of which is its surface area.

Therefore, a large cell (with a smaller SA/Volratio) would not be able to take in necessarysubstances fast enough to survive.

Worksheet 4 Plant Nutritiona) Autotrophs b) heterotrophsc) carbon dioxide d) watere) glucose f) oxygeng) chloroplasts h) chlorophylli) light j) glucosek) polymerization l) starchm) cell walls n) lipidso) minerals (inorganic ions) p) proteinsq) root hairs r) surface areas) osmosis t) xylemu) light absorption v) palisadew) circulation of water & gases throughout the leafx) stomates y) transpirationz) carbon dioxide

Worksheet 5 Animal Nutritiona) enzymes b) sugarsc) amino acidsd) salivary glands, stomach, pancreas & small intestinee) surface area f) small intestineg) liver h) large & flati) long j) bacteriak) cellulose l) sharp, tearingm) short n) hummingbirdso) short & simple



35

Worksheet 61. B 2. B 3. A 4. D 5. D 6. B 7. C

8.Autotrophs are organisms that can make theirown food. example: PlantsHeterotrophs have to eat food made by otherorganisms. example: animals.

9. light energya) Carbon dioxide + water Glucose+ Oxygen

b) 1. It makes all the food, and is the basis of all the food chains

2. It makes all the oxygen in the atmosphere.

10. a) Although glucose is the immediate product ofphotosynthesis, it is rapidly polymerised to formstarch. Therefore, starch is found in largequantities in a photosynthesising leaf, but verylittle glucose could be detected.

b) First the leaf is boiled, then washed in hotalcohol to decolourise it, so colour tests can beseen. Then it can be soaked in iodine solutionto test for starch. A black colour indicates thepresence of starch.

11. Palisade layer: composed of cells neatly and tightlypacked together under the upper epidermis wherethere is maximum light. Each cell is packed withchloroplasts. These features all help the palisadelayer carry out maximum photosynthesis.

Spongy layer: composed of cells that are veryloosely packed. This allows spaces for water &gases to more easily diffuse to/from stomates &veins and so helps supply photosynthesising cells.

12. Grazing herbivores need very long intestines &large caecum, so food has more time in the gutwhile mutualistic bacteria digest the cellulose.

Meat-eating carnivores do not need such longintestines because meat is easier to digest andmore nutritious. They have shorter intestinesbut a stomach that can take in a large meal, lessoften, and digest the high protein meat.

Nectar feeders (e.g. honey-eater birds) eat a diethigh in sugar which needs no digesting at all.They have very simple, short systems since theyonly need to absorb the sugar into theirbloodstream.

Worksheet 7 Animalsa) surface area b) moistc) blood supply d) diffusione) trachea f) bronchig) bronchioles h) alveolii) simple/ less S.A. j) skin & mouth/throat cavityk) spiracles l) tracheam) SA/Vol n) gillso) filaments p) in opposite directionq) counter- r) closeds) heart t) invertebrate

Worksheet 8 Plantsa) stomates b) lenticelsc) root hairs d) water & mineralse) roots f) leavesg) transpirationh)& i) temperature/wind/humidity/lightj) phloem k)translocationl) the plant must expend energym) passive

Worksheet 91. C 2. A 3. D 4. B

5. Transpiration Translocationa) water food nutrients (sugar)b) xylem phloemc) passive active

6. Respiratory system: carries out gasexchange.Excretory system: removal of wastes.Circulatory system: transports substancesaround the body, including gases and wastes...therefore connects with respiratory andexcretory systems.

7.a) Mammal’s lungs have millions of tiny air sacs(alveoli).b) Frog has very simple lungs, but increasesrespiratory surface by using skin, mouth andthroat membranes for gas exchange as well.c) Fish’s gills are made up of thousands of leaf-shaped filaments. Each is flat & thin, giving largecontact area with water flowing past.d) Insects have microscopic, branched air tubes(trachea) that penetrate throughout their body.This gives a large area of contact with air for gasexchange.

8.The main thing is to show that vertebrates havea “closed” system (blood is always inside ablood vessel) while many invertebrates have“open” systems, where the blood leaves bloodvessels and “bathes” the cells at some part ofthe circulation.





36

Worksheet 9 (cont)9.a) stomates, lenticels & root hairsb) Root hairs: these microscopic outgrowthsfrom root cells increase the surface areaavailable. This helps gas exchange (as well aswater absorption).

10.Chemicals containing radio-active “tracers” areintroduced into living things, and any movementis tracked by detecting the radiation producedby the radio-isotope. For example, CO2 gas,containing radio-active carbon-14, is absorbedby a plant leaf, converted to sugar andtransported to storage in the roots. Thismovement can be studied and tracked by theradiations from the carbon-14.

Worksheet 10 Cell Divisiona) growth b) nucleusc) cytokinesisd) is copied/duplicated/replicatede) DNA f) chromosomesg) dissolves h) line upi) spindle j) nucleusk) identical l) parentm) mitochondria & chloroplastn) meristems o) root tipsp) shoot tips (buds) q) larvar) enlargement s) divisiont) metamorphosis u) break down / changev) disks

Worksheet 111. C

2.• Genetic information (DNA) is replicated.• Chromosomes become visible in the nucleus.Nuclear membrane dissolves.• Chromosomes line up in centre of cell. Spindle forms.• Chromosomes pulled apart into 2 identical groups.• Each group forms a new, identical nucleus.• Cytokinesis now divides the cytoplasm &organelles into 2 separate cells.

3.a) “Meristems” located at root tips, buds andcambium.b) Plants grow only at the meristems, andusually grow dis-proportionally in different partsof their body. This means they may drasticallychange their shape & proportions as they grow.In contrast, mammals grow fairly evenly in everybody part and stay more or less in proportion alltheir life.

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