bio answers

1 List three abiotic characteristics and briefl y describe the main differencesbetween aquatic and terrestrial environmentsAnswer Temperature pressure and light availability Temperature in water (aquatic environments) is very constant and any changeis only gradual and very small In contrast temperature on land (terrestrialenvironments) tends to be higher and has large variations over short periodsof time (ie daily variations of 0ndash40degC in the desert) There are signifi cantvariations even over long periods of time such as seasonal variations betweensummer and winter Pressure in aquatic environments increases with water depth to the pointof having crushing effects on organisms at signifi cant depths In terrestrialenvironments only small variations occur in pressure Weather changes cancause small daily fl uctuations Organisms at sea level are under more pressurethan those at high altitudes on land Light availability in aquatic environments is far less than on land where light isin abundance and only cloud cover may reduce the light availability In watermore than half of the light is refl ected from the surface with only 1 per centreaching 100 m depth Turbidity (cloudiness) of the water may affect theamount of light entering and the angle of light may also affect absorption oflight by water (ie sunset versus midday angle of the sun and also seasonalsun angles)2 Briefl y describe how an ecologist would go about recording the distribution ofplants in a rainforest ecosystemAnswer An ecologist would mark out a transect line from one side of the rainforestto the other or covering a representative area of the rainforest They would thenplot the plant species along the transect line in a profi le sketch to scale andidentify the different plant species The ecologist may also choose to do a plansketch (aerial or surface view) They would then analyse the distribution andpatterns formed (ie regularuniform clumped or random) by the different plantspecies in the rainforest

A LOCAL ECOSYSTEMAnswers to end of chapter revision questionsCharacteristics of ecosystems are determined bybiotic and abiotic factors

CHAPTER 1Please note that the following answers are sample answers onlyThere may be many alternative answers to the same question thatare also correct These are examples of correct answersBIOLOGY IN FOCUS

2Copyright copy 2008 McGraw-Hill Australia Permission is granted to reproduce for classroom use

3 Describe an investigation you conducted using the quadrat method List oneadvantage and one disadvantage of this methodAnswer We carried out an investigation to fi nd out how much grass cover thefootball oval had To fi nd this out we used the quadrat (percentage cover)method to estimate grass cover Ten 1 m 1 m quadrats were randomly placedon the oval and grass cover was drawn to scale and plotted for each one Backin the classroom we calculated the average percentage cover of the ten quadratsthat were collected We also measured the area of the oval and then calculated theaverage percentage cover of the amount of area to fi nd out how much grass coverthe football oval hadAdvantage of this methodmdashsimple quick and inexpensive methodDisadvantage of this methodmdashit only takes an estimate by getting arepresentative sample of the oval it is not an accurate measure of the total amountof grass cover just an estimate4 Describe a method you would use to estimate population numbers ofkookaburras in an areaAnswer A method that would be suitable to use to estimate population numbersof kookaburras in an area is the markndashreleasendashrecapture technique This involvesthree main stages fi rst capture mark and release and recapture First capture (a random sample of kookaburras from the population is selected)mdashcapture 20 kookaburras using bird nets Mark and release (marked kookaburras from the fi rst capture are released backinto the natural population and left for a period of time to mix with unmarkedindividuals)mdash tag the 20 kookaburras with leg bands and release them back into their areaand leave them for three weeks to mix with the population Recapture (a sample is captured again to look at the proportion of kookaburrasmarked from the previous sample)mdash after the 3 weeks capture a second sample of ten kookaburras to fi nd thenumber of marked kookaburras from the fi rst captureUse the following formula to calculate an estimate of the abundance ofkookaburras in the areaAbundance number captured number recaptured_________ ___ _____ ___ ______ _ _______number marked in recapture5 Identify two factors that might determine the distribution and abundance ofmangroves in their estuarine environmentAnswer Salinity low oxygen and soft soil tidal changes6 Describe the roles of photosynthesis and respiration in ecosystemsAnswer Photosynthesis is the process where plants use the energy from sunlightto convert the carbon dioxide and water to glucose A small amount of glucose isused by the plant for energy but most of the glucose is used for plant growth orreproductionPlants manufacture their own food through the process of photosynthesis andare responsible for harnessing the energy from sunlight for use in ecosystemsTheir role as producers starts the food chain with high amounts of energy ready

for passing on to consumers This involves removal of carbon dioxide from the airreturn of oxygen to the air and the manufacture of foodBIOLOGY IN FOCUS


The role of respiration is to remove oxygen from the air return carbon dioxideto the air and provide energy Glucose is broken down in the presence of oxygento produce carbon dioxide and water and in particular energy as ATP is released7 Identify two uses of energy by organismsAnswer Firstly sunlight energy is absorbed by producers (plants) and used in theprocess of photosynthesis to produce glucoseSecondly glucose is an energy source and a small amount is used by the plantfor the production of organic molecules (eg proteins and carbohydrates) growthrepair and maintenance fl uid movement and transport and for specialised cellfunction8 Identify the general word equation for aerobic cellular respirationAnswerglucose + oxygen carbon dioxide + water + energy (ATP)many chemical reactions

9 Justify the use of two different sampling techniques to make population estimateswhen total counts cannot be performedAnswer Refer to sample answer using marking criteria1 Quadrat sampling (ie measuring percentage cover of grass)Advantages of using this technique for this purpose are calculating the abundance of plant species is easier than with animals becausethey stay in the one place calculating the entire plant species numbers in most cases would be an endlesstask so this technique saves time using the quadrat technique for taking random samples of the populationprovides an estimate of the population by looking at a representative of thetotal population it is an easy and simple technique for measuring abundance in largepopulations it is an inexpensive technique it causes minimal disturbance to the environmentDisadvantages of using this technique for this purpose are this technique is only suitable for plants and slow-moving animals can be a little time consuming in the calculation of percentage covernumbersafter plotting data in the fi eldConclusion Quadrat sampling is an easy simple time effective and inexpensivetechnique for making population estimates particularly when calculating the totalabundance of plant species With plant populations being in such high numberslooking at a representation of the total population allows estimates to be calculatedinstead of having the almost impossible task of counting individual organismsIt is also easily used in the fi eld and has minimal disturbance to the environmentduring data collection Therefore the quadrat sampling technique is a very useful

and appropriate method for making population estimates when total counts cannotbe performed2 Markndashreleasendashrecapture (eg netting birds for tagging with bands)Advantages of using this technique for this purpose are a simple method that provides an estimate of abundance for animals in largepopulations that are diffi cult to countBIOLOGY IN FOCUS


animals are a little more diffi cult to calculate abundance due to their highmobility and attempting to count every animal species in an area can bevery diffi cult those animals that move around quickly need estimates to be taken Henceestimating abundance is a much easier way of fi nding out roughly how manyanimal species exist in an area can improve accuracy and time effi ciency by using technology can tagmark very mobile animals using tracking bands and tracing theirmovements by GPS systems and the use of satellites capturing animals requires various trapping techniques all designed so thatanimals are unhurtDisadvantages of using this technique for this purpose are only suitable for mobile animals This is a little more diffi cult than the methodused for plants as animals may constantly move around or hide can be time consuming depending on type of species captured method oftagging and time suitable for waiting while the tagged group mixes can be disturbing to the environment for those that are slow moving counts can be made can be traumatic for the animals being trapped and tagged and biases canhappen when designing the trapping methodConclusion The markndashreleasendashrecapture technique is a simple method thatprovides an estimate of abundance for animals in large populations that arediffi cult to count This technique calculates an estimate for animal populationsthat are highly mobile and can be accurately monitored with the support and useof technology such as GPS systems There are various trapping methods availableto allow selection of a suitable method for the chosen animal species and allare designed so that animals are unhurt Therefore the markndashcapturendashreleasetechnique is a simple useful and appropriate sampling technique for makingpopulation estimates when total counts cannot be performed1 Outline the factors that affect numbers in predatorndashprey populations in an areaAnswer Any number and combination of the following factors may affect numbersin predatorndashprey populations in an area number of predators competing for same prey availability of a preyrsquos food birth rate (depending on age of reproductive maturity and number ofreproductive episodes per lifetime) death rate (increased by exposure to disease) number of males and females size of ecosystem for supporting the predator and prey numbers movement between ecosystems number of shelter sites available

Unique aquatic and terrestrial ecosystems CHAPTER

2BIOLOGY IN FOCUS


2 Identify one example of allelopathy parasitism mutualism and commensalismin an ecosystem and briefl y describe the role of organisms in each type ofrelationshipAnswer Allelopathy an example of allelopathy (the production of specifi cbiomolecules by one plant that can be benefi cial or detrimental to anotherplant) is the black walnut which releases a chemical that inhibits respirationThe chemical is found in all parts of the plant but it is concentrated in the budsand roots Plants exposed to this chemical exhibit symptoms such as wiltingyellowing of foliage and eventually death Parasitism an example of parasitism (a relationship where one speciesbenefi ts and the other is harmed) is the fl ea and the dog Fleas (ectoparasites)live on the surface of their host (dog) obtaining food and shelter They feedupon the fl uids but do not usually kill the host organism they are feeding onas this would destroy their food supply The host remains alive with little harm Mutualism an example of a mutualistic relationship (a relationship where bothspecies benefi t from the association) is within reef-building corals which havesymbiotic algae within their tissues that provide the yellow-brown pigmentsthat give the coral its colour The algae live reproduce photosynthesise anduse the waste products of the host In turn the coral uses oxygen and foodproduced by the algae during photosynthesis to grow reproduce and form itshard skeleton which is the basis of the reef The formation of the Great BarrierReef depends on this mutualistic relationship When corals are stressed theyexpel the algae which in turn cause the coral to starve and die leaving whiteskeletons Commensalism an example of commensalism (a relationship where onespecies benefi ts and the other is unaffected) is the epiphyte group such asmosses small ferns and orchids which can be seen on tree trunks in moistforests They appear to benefi t from living on the trunk of the host tree bycatching rainwater for dissolving nutrients and being closer to light Epiphytesdo not appear to affect the host tree negatively The epiphyte benefi ts but thehost is unaffected3 Describe the role of decomposers in ecosystemsAnswer Decomposer organisms use the energy of dead organisms for foodand break them down into materials that can be recycled for use by otherorganisms Bacteria and fungi in the soil are very important because they returnnutrients to the soil when they decompose dead animals and plants The cyclehighly important in this process is the nitrogen cycle as nitrogen is essential toall living things4 Identify the difference between food chains food webs and pyramids of numbersbiomass and energy Draw an example of eachAnswer

Food chains show the energy movement from one living thing to another(refer to Fig 213 on page 35 in the textbook or below) Grass rarr grasshopper rarr kookaburraIt describes the feeding order or which plants or animals eat or are eaten byother animals However food chains are not isolated in ecosystems they aremore realistically shown as a food webBIOLOGY IN FOCUS


Food webs show complex food interactions in an ecosystem They are madeup of two or more food chains (Refer to Fig 214 on page 35 in the textbook) A pyramid of numbers shows a food web and the different trophic levels andthe actual number of organisms at each level (Refer to Fig 218 on page 37in the textbook) A biomass pyramid shows the amount of biomass (total amount of livingmaterial present) through each level of the food chain At each level energy(heat) and matter (food and wastes) are lost (90 per cent) (Refer to Fig 218on page 37 in the textbook) Different to the pyramid of numbers and the biomass pyramid is the pyramidof energy Not all the energy and material taken in by one trophic groupis passed on to the next because not all organisms at one trophic level areconsumed by the next there are also losses of heat Energy fl ow indicates thefood value of trophic levels more accurately than either numbers or biomass(Refer to Fig 218 on page 37 in the textbook)5 Defifi ne the term adaptation and discuss the problems associated with inferringcharacteristics of organisms as adaptations for living in a particular habitatAnswer An adaptation is a feature of an organism that makes it suited to itsenvironment It is any characteristic that increases an organismrsquos likelihood ofsurvival and reproduction relative to the organisms that lack the characteristicCharacteristics of present-day organisms are products of millions of years ofchange where ancestors have received adaptations to survive in different habitatsAn organismrsquos current characteristics may have been inherited a long time agowhen it existed in a different habitat now the organism still possesses thatcharacteristic (or adaptation) but it is not of any use or related to its survival inits current habitat Dolphins and whales are well adapted to life in water howeverthey possess lungs which are characteristic of land-dwelling animals If theseanimals have occupied a very different environment to that of their ancestorsthen we cannot infer that the lungs are any sort of adaptation to their currentenvironment but one inherited over time when they could possibly have beenland-dwellersTo be able to determine if a characteristic is an adaptation biologists needto study the organismrsquos environment It is diffi cult to relate a characteristic to aspecifi c feature of an organismrsquos environment when we do not know the exacthabitats its ancesters have lived in over generationsSometimes adaptations may be obvious (like the stick insect camoufl aging itselfto its environment) and sometimes not Some characteristics may have no benefi tto the organism in a particular habitat or are just not adaptations at all It may bediffi cult to be certain how one characteristic benefi ts the organism in a particular

environmentInterpreting the characteristics of organisms from fossil evidence in particularmay lead to incorrect assumptions For example the extinct organism stegosauruspossessed bony plates along its back Some suggest that this characteristic was anadaptation to its competitive environment and used for defence Others suggest itwas simply used to attract mates or perhaps even used for thermoregulationTherefore we must be careful not to assume that all characteristics of organismsare adaptations to their present day habitat or environmentBIOLOGY IN FOCUS


6 Identify two named plants and two named animals with adaptations to factorsin their environmentAnswerPlantsmdashxerophytes are plants that have adapted structurally to dry environmentsby reducing the surface area of their leaves in order to minimise water lossFor example the cactus has small spiky leaves to reduce loss of water pigface found on sand dunes has fl eshy stems which store waterAnimalsmdashadaptations to a lack of water may vary For example kangaroos do not sweat so they avoid losing water through sweating bilbies hide in burrows to reduce water loss by evaporation most desertmammals are nocturnal to reduce exposure to daytime temperatures7 Identify and describe in detail adaptations of a named plant and a named animalfrom the local ecosystem you studiedAnswer This answer will depend on the type of ecosystem you studiedThe sample answer will assume a mangrove ecosystem was studiedPlant examplemdashgrey mangrovesGrey mangroves use their roots leaves and reproductive methods in order tosurvive in a harsh changing intertidal environment of low oxygen soft soils andsaline conditionsGrey mangroves live in shifting environments where tides and fl oods constantlymove the mud in which they live destabilising the trees Grey mangroves havepneumatophores (aerial roots) which are fi lled with spongy tissue and smallholes that provide structural support and transfer oxygen from the air to the rootstrapped below the ground in low oxygen soil The roots are also adapted toprevent the intake of a high amount of salt from the waterGrey mangroves have leaves with glands that excrete salt They can tolerate thestorage of large amounts of salt in their leaves which are later dropped when theamount of salt gets too high They can also restrict the opening of their stomata(pores in the leaves) responsible for regulating the exchange of gases and waterduring photosynthesis This conserves the fresh water within the leaves which isvital for survival in a saline environment Grey mangroves are also able to reducetheir leaf surface exposure to the hot sun by turning their leaves side on Thisreduces excess water loss through evaporationAnimal examplemdashmangrove crabsMangrove crabs burrow into the soft mud to gain protection from both

dehydration and predators They use the water in their burrows to keep theirgills moist and as a barrier to the hot sunThe fi ddler crab has a distinctive single large claw in the males It burrowsin the intertidal zone and as the tides recedes it comes out to feed on the algaemicrobes and organic matter Sometimes it may drag leaf litter into its burrowto be eaten This use of the burrow (and for the male the possession of a largeclaw) provides protection against predators in a very vulnerable environmentBeing intertidal makes the crab vulnerable and exposed at low tide It must avoiddehydration and predation by burrowing into the moist mudBIOLOGY IN FOCUS


8 Describe and explain the short-term and long-term consequences on theecosystem of species competing for resourcesAnswerShort-term consequencesWhen two species compete for a resource the short-term effect is a decreasein population numbers In most instances one species is more successful thanthe other and so one species fi nds that its population numbers have droppedmore signifi cantly than the other (due to an increase in deaths and a decreasein reproduction rates) Depending on the continued success of the one speciesover the other this trend may continue However depending on the supply ofthe resource they are competing for the ability of the lsquolosingrsquo species to adaptby occupying a different niche or other environmental factors this trend maychangeLong-term consequencesIf the trend of one species successfully out-competing another species continuesthe long periods of decreased reproduction rates and increased deaths willeventually lead to the elimination of the lsquolosingrsquo species in that area and on thelarger scale possible extinction9 Identify three impacts of humans in the ecosystem you studiedAnswer The answer to this question depends on each individual area that youstudied however a list of possible impacts which you may have observed threeof are listed below land clearance and habitat fragmentation (eg clearing of large areas ofecosystems) slash and burn agriculture (eg clearing with burning) integrated pest management (eg use of pesticides biological control) land and water degradation (eg poor waste management dams irrigationrunoff roads and mining) erosion (eg livestock clearingploughing roads and housing development) soil acidifi cation (eg chemical runoff into soil water) soil and water salinity (eg irrigation runoff) polluting the atmosphere (eg industrial gases and vehicle emissions) introduced species (eg fox rabbit cane toad lantana Patersonrsquos curse orprickly pear)10 Describe how you measured three different abiotic features in the ecosystemyou studied using appropriate instruments and discuss how these factors maydetermine the distribution of organismsAnswer Air temperature (thermometer in degrees Celsius)mdashair temperature was takenat 30 minute intervals and averaged for each zone Light intensity (light metre)mdashlight intensity was measured at intervals the same

as temperature and averaged out for each zone Soil salinity (silver nitratemdashprecipitation grade)mdashsmall samples of soil weretaken from each zone shaken in a test tube with distilled water then fi ve dropsof silver nitrate were added to the test tube once the sediment had settled aftershaking The amount of white precipitate (cloudiness) was graded on a scale of1ndash5 for salinityBIOLOGY IN FOCUS

1 (a) Clarify what is meant by a scientifi c theory(b) Describe how you would go about validating a scientifi c theory(c) State the cell theoryAnswer(a) A scientifi c theory is the general idea or reasoning provided by scientiststo explain a phenomenon based on observation and experiment(b) It may be validated by testing whether it holds true for predictions (bothby experimentation and observation) and whether or not it is supportedby new evidence that is found(c) All living things are made of cells Cells are the basic structural and functional unit of all organisms All cells come from pre-existing cells2 Before the development of the cell theory it was commonly believed that livingorganisms could arise by spontaneous generation(a) Outline the theory of spontaneous generation(b) Describe experimental evidence that was used to discount this theory(c) Explain the role that the invention of the microscope played in the dismissalof the theory of spontaneous generationAnswer(a) This past scientifi c theory suggested that life can arise from non-livingthings independent of any parent being presentmdashfor example animalssuch as maggots could arise from rotting meat(b) The experiment of Francisco Redi (1668) successfully showed that maggotsonly appear in meat that has been exposed to fl ies and that they did notspontaneously appear in meat that had been covered and not exposedto fl ies(c) The microscope revealed the cellular nature of living things and madepeople aware of the existence of microscopic structures By being able tosee microscopic living cells such as eggs and sperm cells and microscopicorganisms people could understand that microscopic living structures suchas these must be present in order for new living organisms to arise

3 Describe the contributions of Robert Hooke and Robert Brown in thedevelopment of the cell theory (Find a reliable way of remembering whichlsquoRobertrsquo did what)AnswerRobert Hooke observed cork under a light microscope and noted thecompartmental nature of this tissue He named the compartments lsquocellsrsquo (150 yearsprior to the cell theory) Hooke also further developed the compound microscopeallowing better viewing of microscopic structures such as cells and their nucleiRobert Brown discovered the nucleus (8 years before the cell theory) He described

it as a large body observed in the cells of the plant material that he was studyingThe observation of the regular placement of nuclei in plant tissue (bySchleiden) and in animal tissue (by Schwann) suggested to them that all livingtissue has a similar basismdashthat is it is made of compartments called cells and thatthese cells are the basic unit of all living things The division of the nucleus insidecells led Virchow to add that all cells arise from pre-existing cells (16 years later)Therefore the discovery of the nucleus by Brown the naming of cells by Hookeand his improvements on the compound microscope played important roles in thedevelopment of the cell theory(Any suitable way of remembering which Robert did what is acceptable for thesecond part of the answer to this question)4 Discuss why biologists have continued to use light microscopes since theinvention of the electron microscopeAnswer The light microscope magnifi es things and although it does not showas much detail as the electron microscope it is still useful because it shows moredetail than could be seen with the naked eye The light microscope is moreaffordable and accessible to school students and the general public It is easier touse because it involves simpler techniques for preparation of slides to be viewedand can be used to view living things as well as non-living or dead things5 Put the following words into order of size from the smallest to the largestorganelles molecules cells atoms and organismsAnswer atoms molecules organelles cells organisms6 Compare the detail seen with a light microscope in plant and animal cells whenviewed under a light microscopeAnswerTable 16 Parts of cells visible under a light microscopePart of cell Plant cell Animal cellBoundary Cell wall and membrane Cell membraneOrganelles Nucleus chloroplasts vacuolevisible in cytoplasmNucleus no other organellesvisible cytoplasm may appeargranularCell shape Regular IrregularVacuoles Large permanent vacuolesurrounded by tonoplast andcontaining cell sapNo large vacuoles visibleBIOLOGY IN FOCUS


7 State whether the each of the following photographs was viewed under a light oran electron microscope and whether it shows plant or animal cells Justify youranswers(a) (b)(c) (d)Answer(a) Plant cells regular shape (square) cell walls visible(b) Plant cells regular shape chloroplast present (stained) large vacuolesvisible cell walls visible(c) Animal cells irregular shape cell walls visible chloroplasts presentlarge vacuoles visible

(d) Plant cells regular shape cell walls visible chloroplasts present largevacuoles visibleBIOLOGY IN FOCUS


8 Using the method described for comparative diagrams on page 84 draw acomparative diagram of(a) a light and an electron microscope(b) a chloroplast and a mitochondrionAnswer(a) Draw diagrams and then complete comparative labelling as indicatedbelowLabels on light microscopeLabels in centre commonto both diagrams Labels on electron microscopeLight source Eye Source of electronsObjective lenses Specimen Electromagnetic lensesFinal image on photographicplate or screenFinal image reaches eye

(b)104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644 10486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644104864410486441048644

9 Identify the two types of nucleic acid found in cellsAnswer DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)BIOLOGY IN FOCUS


10 Analyse the micrograph below and assess whether it shows plant or animal cellsJustify your choiceAnswerAnimal cells irregular shape cell membrane but no cell wall no large vacuolesor chloroplasts visibleBIOLOGY IN FOCUS


1 Draw a diagram of a plantanimal cell as seen under the electron microscopeLabel each part of the cell Identify what chemicals make up each part of thecell and using a different-coloured pen write the name of the chemicals nextto each respective part that has been labelledAnswerDraw diagram and label as indicated belowPart of cell labelled Chemical compositionCell wall (plant cell only) Carbohydrate cellulose (sometimes alsocontains lignin)Cell membrane (and any other membraneslabelled eg nucleus mitochondria ERvacuoles and Golgi bodies)Protein and lipidNucleolus RNA and proteinLysosome Protein and lipid (membrane)Protein digestive enzymes (inside)Mitochondria Protein and lipid (membrane)

Small amounts of glucose

Small amounts of DNA (inside matrix)

Chloroplasts (plant cells only) Protein and lipid (membrane)Chlorophyll (in thylakoids)Carbohydrate stored starch (in stroma)Vacuole Protein and lipid (membrane)Water

Chloride ions and other dissolved salts (in sap)

Nucleus Protein and lipid (membrane)DNA and protein (chromatin)

2 Draw a table to compare the organic chemicals found in cells Your table shouldcompare the monomers of each compound the chemical elements (atoms) thatcomprise that compound where in the cell each is found and two functions oruses of the chemicals in cellsChemical MonomerElements of which itis composedParts of cell in whichit is found Main use or function in cellsCarbohydratesglucoseGlucose Carbon hydrogen andoxygen(2 hydrogen1 oxygenratio)Mitochondria Chemical respiration as anenergy source for cellsCarbohydratestarchAs starch granulesin chloroplasts andcytoplasm Stored starch is an insolubleform of stored energy thatdoes not affect the osmoticbalanceCarbohydratecelluloseCell wall of plant cells Structural component of cellwallsmdashprovides support forplant cells and creates wallpressure to ensure turgidityLipids Glycerol and fattyacidsCarbon hydrogen andoxygen(no 21 ratio)Cell membrane dropletsin cytoplasm and allmembranes of organelles Structural part of allmembranes Form of stored energy as fator lipid droplets in cytoplasmProteins Amino acids Carbon hydrogenoxygen nitrogensometimes phosphorousand sulfurCell membraneall membranes oforganelles basis ofprotoplasm and allenzymes Structural part of allmembranes Structural part of cytoplasmand nucleoplasm Enzymes control all

metabolic reactions in cellsNucleic acids Nucleotides ofDNA and RNACarbon hydrogenoxygen and nitrogenChromatin in the nucleus(DNA)Ribosomes (RNA) DNAmdashstores codedinformation to controlsall cell activities containshereditary information andensures it is passed on fromone generation to the next RNAmdashplays a role in proteinsynthesisChloride ions NA Chloride (Clminus) Dissolved in thecytoplasm in the cell sapof vacuoles Used in the regulation ofwater balance by osmosis incells assists with membranefunctioning (eg muscle andnerve cells in animals)Lignin NA NA Cell wall of plant cellsparticularly woody tissue Gives extra strength andsupport because it iswaterproof it helps directwater movement in roots

3 Identify three main components of a cell membrane and describe how eachcontributes to membrane functioningAnswer Cell membranes are made up of a lipid bilayer which forms the basis of the membrane and is not rigid instructure It allows direct diffusion of some substances into and out of cellsThe lipid bilayer is partly responsible for the selectively permeable nature ofthe cell membrane making it diffi cult for substances that are lipid insoluble(hydrophilic) or too large to pass through It also allows proteins that formchannels to move about within the membrane The fl uid nature of themembrane allows it to join with other membranes and reseal to fl ow aroundparticles and repair damage or growBIOLOGY IN FOCUS

8 proteins which are scattered within the lipid bilayer act as membranetransporters creating active carrier systems channels or pores through whichselected materials can cross the membrane by means of facilitated diffusion(channels and carrier proteins) osmosis (aquaporins) and active transportTherefore the protein component also contributes to the selectively permeablenature of the membrane essential to cells for the exchange of substances surface components (carbohydrates) in the form of glycolipids andglycoproteins which play a role in cell recognition They enable organisms todistinguish between parts of their own bodies (lsquoselfrsquo) and foreign or invadingcells (lsquonon-selfrsquo) They may also act as receptor sites for the uptake of certainmolecules4 Complete the following table comparing the structure and function of a cellmembrane with that of a cell wallAnswerTable 28 Comparison of cell membranes and cell wallsCell membrane Cell wallChemical composition A complex structure made ofprotein and lipid (much thinner thana cell wall)A simpler structure made mainlyof strands of the carbohydratecellulose also contains pectin and

may have additional thickening suchas lignin and suberinWhere it is found Directly surrounds the cytoplasmand is the outer boundary in animalcells and forms part of the boundaryin plant cellsDirectly surrounds the cellmembrane in plant cells and formsthe outermost boundary in plantcellsFunction Controls the movement ofsubstances into and out of cells andis selective in what substances canpass throughProvides support and shape limitsthe expansion of cells and plays arole in cell turgidity Allows waterand most molecules to pass freelyinto and out of cellsAccess to molecules Selectively permeable it has poresthrough which substances canpass It also has receptors on thesurface for the passage of somesubstancesPermeable has pits with strandsof cytoplasm passing through themto allow passage of substancesbetween cells

5 In the form of a table compare the processes of diffusion osmosis and activetransport under the following headings Type of substances that move Concentration gradient along which they move Energy requirements Only across selectively permeable membranesmdashyes or no Examples in living organismsBIOLOGY IN FOCUS


AnswerComparing movement across membranesFeature Diffusion Osmosis Active transportType of substancesthat moveAny molecules Water only Selected substances for whichthere are carriersConcentration gradient From low to high concentration From low to high concentration From high to low concentrationEnergy requirements Passive movementmdashno energyinput requiredPassive movementmdashno energyinput requiredActive movementmdashrequiresinput of cellular energy (ATP)Selectively permeablemembrane neededNo Yes YesExamples in livingorganismsMovement of gases into or out of lungs orgills salts into roots of plants glucose amino acids fromdigestive tract into bloodstreamMovement of water into plant roots out of plant leaves out of lungs duringbreathingMovement of substances

against a concentration gradient(eg uptake of digestive nutrientsand excretion of wastes)

6 If solution X contains more dissolved substances than solution Y what process isinvolved in moving(a) water from Y to X(b) solutes from X to Y(c) solutes from Y to XAnswer (a) osmosis (b) diffusion (c) active transport7 If we cut two identical cubes of potato and leave one to stand in water while theother stands in a 20 per cent glucose solution for 12 hours predict which willhave the greater mass and explain why (Hint In each case in which directionwill water molecules move)Answer The cube of potato in the water will have a greater mass becausewater will move from a higher water concentration in the pure water to alower concentration in the cells of the potato (cells contain dissolved nutrients)by osmosis The potato cube will swell with water and therefore have thegreater mass8 The terms turgid and fl accid are used to refer to the condition of plant cellsDraw a labelled diagram to illustrate what is meant by each of these termsAnswercell body shrinksfrom cell wall (flaccid)hypertonicsolutionhypotonicsolutionisotonicsolutioncell contentsgives little supportnormal turgid cellCell shape as determined by osmotic pressureBIOLOGY IN FOCUS


1 Identify where the oxygen gas produced by photosynthesis comes fromDescribe how it is producedAnswer The oxygen comes from water During the light phase (photolysis)radiant energy is absorbed by chlorophyll which emits excited electrons Theenergy of one of these electrons is used to split a water molecule into its hydrogenand oxygen components The oxygen atom combines with another oxygen atomfrom an adjacent chlorophyll molecule to form oxygen gas which is then releasedas a by-product2 List the chemical products of photosynthesisAnswer Products of photosynthesismdashglucose and oxygen (and water)3 Write the overall word equation for photosynthesisAnswercarbon dioxide + water light energy glucose + oxygen (+ water)chlorophyll

4 Explain why the light-independent phase must occur during the day and notat nightAnswer The light-independent phase relies on the products of the light phase andso it takes place immediately following the light phase There is no light at night

and so no radiant energy is availablemdashas a result the light-dependent phase cannotoccur and without the products of this phase the light-independent phase cannottake place5 Describe two ways in which plants increase the surface area of their absorbingstructuresAnswer The absorbing structures of a plant are the roots and the leaves Thesurface area of the roots is increased by lateral branching and in the root hairzone by the outer surface of the epidermal cells becoming extended to formfolds called root hairs The surface area of a leaf is increased by its fl attenedblade-like shape6 Explain why an increase in surface area is necessary for the normal functioningof plantsAnswer Plant nutrition depends on the absorption of water and mineral saltsby roots (nutrient uptake) and the absorption of light and gases by leaves forphotosynthesis The uptake of nutrients and gases is largely as a result of passivemovements (osmosis and diffusion) which are slow By increasing the surface areaof absorptive structures there is an increase in the overall rate of absorption ofthese substances which are essential to the survival of the plant7 Identify the processes necessary for the uptake of water and mineral salts byrootsAnswer Water uptakemdashosmosis Mineral salt uptakemdashdiffusion and active


3 Describe an investigation you conducted using the quadrat method List oneadvantage and one disadvantage of this methodAnswer We carried out an investigation to fi nd out how much grass cover thefootball oval had To fi nd this out we used the quadrat (percentage cover)method to estimate grass cover Ten 1 m 1 m quadrats were randomly placedon the oval and grass cover was drawn to scale and plotted for each one Backin the classroom we calculated the average percentage cover of the ten quadratsthat were collected We also measured the area of the oval and then calculated theaverage percentage cover of the amount of area to fi nd out how much grass coverthe football oval hadAdvantage of this methodmdashsimple quick and inexpensive methodDisadvantage of this methodmdashit only takes an estimate by getting arepresentative sample of the oval it is not an accurate measure of the total amountof grass cover just an estimate4 Describe a method you would use to estimate population numbers ofkookaburras in an areaAnswer A method that would be suitable to use to estimate population numbersof kookaburras in an area is the markndashreleasendashrecapture technique This involvesthree main stages fi rst capture mark and release and recapture First capture (a random sample of kookaburras from the population is selected)mdashcapture 20 kookaburras using bird nets Mark and release (marked kookaburras from the fi rst capture are released backinto the natural population and left for a period of time to mix with unmarkedindividuals)mdash tag the 20 kookaburras with leg bands and release them back into their areaand leave them for three weeks to mix with the population Recapture (a sample is captured again to look at the proportion of kookaburrasmarked from the previous sample)mdash after the 3 weeks capture a second sample of ten kookaburras to fi nd thenumber of marked kookaburras from the fi rst captureUse the following formula to calculate an estimate of the abundance ofkookaburras in the areaAbundance number captured number recaptured_________ ___ _____ ___ ______ _ _______number marked in recapture5 Identify two factors that might determine the distribution and abundance ofmangroves in their estuarine environmentAnswer Salinity low oxygen and soft soil tidal changes6 Describe the roles of photosynthesis and respiration in ecosystemsAnswer Photosynthesis is the process where plants use the energy from sunlightto convert the carbon dioxide and water to glucose A small amount of glucose isused by the plant for energy but most of the glucose is used for plant growth orreproductionPlants manufacture their own food through the process of photosynthesis andare responsible for harnessing the energy from sunlight for use in ecosystemsTheir role as producers starts the food chain with high amounts of energy ready









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