Biology Unit 4 Past paper questions 2010-2014

A large size results in snow geese being adapted for colder conditions. Explain how. (2 marks)

-Smaller surface area to volume ratio/ more fat -Lose less heat (to the environment)/ for insulation -when sitting on eggs

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Explain how natural selection might have effected the percentage (increase) of white snow geese in greater snow areas? (3 marks)

-snow melts further north -more snow means white geese are able to camouflage -predation linked to survival /reproductive success

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Percentage of white snow geese decrease as climate change occurs and snow begin to melt. Explain how. (2 marks)

-Snow begins to melt so there is less snow -white geese decreasing as they are unable to camouflage as well/ blue geese are at more of an advantage

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Name the three different population pyramids. (3 marks)

- Stable birth rate and death rate are balanced, increasing where birth rate is higher than death rate and decreasing where death rate is much higher than birth rate and a higher elderly population

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Describe how microorganisms make carbon from starch available to plants (2 marks)

-extracellular digestion -starch to glucose monosaccarides -respire product of digestion -produce CO2 from respiration

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Definition of Population (1 mark)

All organisms of all species in a habitat at one time

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Explain the Survival curve for England in 1750 (2 marks)

-more disease -poor sanitation -poor medical care -higher death rate amongst young

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Describe how you would use quadrants at random (2 marks)

use two tapes and place them at right angles to each other -obtain random co-ordinates using a random number generator by a computer or calculator -place quadrant at intersection

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How would you decide the number of quadrants to use in order to collect representative data (2 marks)

- enough to calculate a running mean - enough to carry out a statistical test -long enough sample/results to make sure its reliable and remove/distinguish effect of anomalies

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Name ONE step which CO2 is produced (1 marks)

-Kreb Cycle -Link Reaction -Pyruvate to Acetylecoenzyme A

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Measuring rate of CO2 production of cells, scientist kept temperature constant throughout investigation. Explain why. (2 marks)

-reactions controlled by enzymes -rate decreases due to less kinetic energy/ few collisions/ few E-S complex formed

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Cells placed in a nitrogen gas environment. explain the pathway played by reduced NAD. (2 marks)

-Requires hydrogen / electrons are reduced -hydrogen reduces NAD -Reduced NAD is oxidised and reduces pyruvic acid.

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Rate of CO2 is higher when cells are placed in a nitrogen gas environment. Explain why? (3 marks)

-respire anaerobically -produce less ATP -more anaerobic respiration -more CO2 produced

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Explain why scientist obtain results at random? (1 mark)

-to avoid bias and allow a statistical test to be carried out

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You could use a scatter diagram to check the repeatability of measurements made by two observers. Describe how. (2 marks)

-Scatter diagram of one set of results against the other - expect to see points lying near/close to line of best fit/ positive correlation

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Use the term chance and probability in regards to statistical test (2 marks)

-Statistical tests determines the probability of results being due to chance and allows null hypothesis to be accepted/or rejected

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In the light-dependent reaction of photosynthesis, light energy generates ATP. Describe how. (5 marks)

-Light energy excites electrons in chlorophyll and raises electrons energy level -electrons pass down electron transfer chain -electrons reduce carriers which includes a series of redox reactions -in the thylakoids -energy released -ADP + P = ATP

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Describe and explain why the efficiency of energy transfer is different at different stages of transfer. (6 marks)

-Some light fails to strike -wrong wavelength -ef of photosynthesis is 2% -respiratory loses -heat loss -ef of transfer in consumer greater than producer -ef lower in older animals -carnivores use more of their food than herbivores

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Explain how intensive stock rearing of domestic livestock increases net productivity. (4 marks)

-Slaughtered when still growing/ while young -Fed on concentrate diet -movement restricted -kept inside so less respiratory loses -genetically selected for high productivity

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Nitrogenase catalyses the reduction of nitrogen during nitrogen fixation. Nitrogen gas is the usual substrate. Name the product. (1 mark)

-Ammonia

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Nitrogenase will catalyses reactions involving other substances. Explain what this suggests about the shapes of the molecules of these other substances. (2 marks)

-Will have a similar shape/ tertiary structure/ complementary shape to the active site -Fit/bind with active site/ forms E-S complex

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How do you calculate size of a population once you have done mark-release-recapture

- (size of total first sample x size of total second sample/ no. of marked individuals ) x100

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Name the assumptions made with the mark-release-recapture technique

-no of marked to unmarked is representative of whole population -marked individuals from first sample evenly disperse themselves within population -population has a definite boundary -few deaths & births -method of marking is not toxic -mark not lost

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Whales meet surface of the ocean. Scientist can obtain small samples of DNA. How can you use this and apply it to the mark-release-recapture technique? (2 marks)

-Recording DNA/ base sequence is the same as marking. -Finding identical base sequence shows animal has already been caught

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What does the Hardy-Weinberg principle predict? (3 marks)

-The frequency/ proportion of alleles -will stay constant from generation to generation -providing no mutation/ no selection/population genetically isolated/ mating random/no migration

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Describe the part played by the inner membrane of a mitochondria in producing ATP (3 marks)

-Electrons transferred down electron transport chain -provides energy to take protons/ H+ into space between membranes -Protons pass back into matrix through ATPase -Enrgy is used to combine ADP and Phosphate to produce ATP

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Why is solution of a cell suspended in isotonic? (1 mark)

-Prevent damage to cell by osmotic gain or loss due to difference in water potential

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What is the terminal acceptor? (1 mark)

-Oxygen in the electron transport chain

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If standard deviations do not overlap what does this mean?

-Not due to chance

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Use the words probability and chance to explain the meaning of significantly (p < 0.05) (2 marks)

-There was a probability of less than 0.05/ 5% -that the difference is due to chance

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The ratio of the dry biomass of animals to the dry biomass of seaweed is always a lot less than one. Explain why (2 marks)

-Plants are producers/ first trophic level -loss of energy between trophic levels -as a result of respiration/heat loss to environment

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The concentration of CO2 in the air at different heights above ground in a forest changes over a period of 24 hrs. Use you knowledge of photosynthesis to explain why. (5 marks)

-High conc of CO2 linked with night -No photosynthesis in the dark -plants respire at night -in light net uptake of CO2 is greater than photosynthesis/ respiration -decrease in CO2 conc with height -fewer leaves on ground/less photosynthesis

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in the light independent reaction of photosynthesis, the carbon in CO2 becomes carbon in trios phosphate. Describe how. (5 marks)

- CO2 combines with ribose/RuBP -produce two molecules of 3GP -reduce to TP -requires NADP -energy from ATP

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Microorganisms make the carbon polymers in dead worm available to cells of leaf. Describe how. (5 marks)

-Microorganisms are saprophytes -secrete enzymes/ extracellular digestion -absorbs products of digestions -respiration produces CO2 -CO2 taken up by leaves -through stomata

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Explain what is meant by the ecological term population. (1 mark)

-Number of organisms of one species in a habitat at one time

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In 1990 the life expectancy was 70 years, give one reason why that has now changed (1 mark)

-Improved medical care -Improved nutrition -Lower infection rate -Less disease -Improved sanitation

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Explain what is meant by a recessive allele (1 mark)

-Only expressed/shown in phenotype when paired

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What is meant by co-dominant alleles (1 mark)

-Both alleles are expressed/ shown in phenotype

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What measurements does a student need to make to calculate the rate of respiration in mm3 of oxygen g-1h-1? (3 marks)

-distance drop moves and time -mass of animal -diameter of tube

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RFI is the residual food intake and it is the difference between amount of food an animal actually eats and its expected food intake. What is a benefit of a cattle having a low RFI? (2 marks)

-Reduce cost -Less feeding/less land use/ more growth rate with same amount of food

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-Why is the RFI values negative? (1 mark)

-Amount of food taken is less then expected

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Two factors were controlled, food and temperature. Why? (4 marks)

-Food= may vary in protein/fat/carbs, may affect absorption/growth/food intake -Temperature= Will affect heat loss/respiration, maintain regulated body temperature, more food can be used for growth

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Scientist are investigating RFI and methane production. Suggest a null hypothesis (1 mark)

-RFI does not affect methane production

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Selectively breeding cattle with low RFI may help limit global warming. Explain how. (2 marks)

-Cattle with low RFI produces less RFI -Methane is linked to greenhouse gas effect/ is a greenhouse gas

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Succesion occurs in natural ecosystem. Describe and explain how succession occurs. (5 marks)

-Colonisation by pioneer species -change in environment -enables other species to colonise -change in diversity -stability increases -climax community

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Describe the advantages and disadvantages of biochemical agents to control pest (5 marks)

-A=specific, only needs 1 application, maintains low population, pests do not develop resistance, does not leave chemical in the environment, can be used in organic farming -D= Does not get rid of pest completely, may become pest, slow acting

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Change in the environment can lead to speciation. Explain how different species evolve. (5 marks)

-Geographical isolation -separate gene pools -variation due to mutation -different environments -selection for advantageous alleles -different reproductive success -leads change in allele freq -occus over a long period of time

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-Write down a simple equation to show how ATP is formed from ADP. (1 mark)

-ADP + Pi => ATP

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Give two ways in which ATP makes a suitable source of energy (2 mark)

-Energy released in small amounts -Soluble -Involves a single reaction

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Human synthesise more than their body mass of ATP each day. Explain why it is necessary for them to synthesis huge amounts of ATP (2 marks)

-ATP is unstable -ATP cannot be stored -(named process) uses ATP -ATP only releases a small amount of energy at a time

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Write an equations using 'Gross productivity' & 'Net productivity"

-Gross productivity = Net productivity - Respiratory loss

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How do animals store extra nutrients absorbed? (1 mark)

-Stored as fat -Used for growth/movement/reproduction

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Explain the consequence of leaching of fertiliser into the pond and lakes (3 marks)

-algal bloom -light blocked out -plants can not photosynthesise -sapriobionts break down dead organisms -bacteria use up oxygen

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Give one advantage of using natural fertilisers than artificial fertilisers (1 mark)

-Acts as soil conditioner -Contains other elements -production of artificial fertilisers -less leaching

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What is meant by "birth rate" (1 mark)

-Birth rate per 1000 of the population per year

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Describe the role of bacteria in making nitrogen in dead leaves available to growing plants (5 marks)

-Saprobiotic microorganisms -break down proteins -extracellular digestion -ammonia produced -ammonia converted to nitrite -nitrifying bacteria

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Clearing the forest and burning vegetation affects CO2 levels. Describe and explain why. (4 marks)

-CO2 concentration increases -less photosynthesis -less CO2 removed -burning produces CO2

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During photosynthesis, CO2 is converted into organic substances. Describe how. (6 marks)

-CO2 combines with RuBP -produce two molecules of 3GP -reduced to TP -using reduced NADP -energy from ATP -TP => organic substance/glucose -Calvin Cycle/light independent reaction

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Explain what is meant by a community (1 mark)

-All the species of all the population of all organisms

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Ecologist used the mark-release-and recapture technique to estimate the population size. Suggest how. (3 marks)

-capture sample, mark and release -appropriate method of marking -take second sample and note how many of them have been recaptured -then do population equation (must be written)

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If animals are breeding, give one reason why mark release and recapture technique will not give reliable results (1 mark)

-population size is increasing/ changes between first and second sample

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Suggest how the shape of a mouth is an adaptation to a nice of a fish (2 marks)

-has different way of feeding -competition between spies/ interspecific competition is reduced

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Energy from the sun may ultimately end up in plant dead matter. Explain how. (2 marks)

-Photosynthesis/ light dependent/independent reaction -carbon containing substances

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Describe how you would investigate the distribution of marram grass from one side of a dune to another? (3 marks)

-Transect/line/tape from one side to another 0place quadrants in regular intervals -count plants/percentage cover

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What does abiotic mean? (1 mark)

-Non living

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Other than temperature suggests one other abiotic factor. (1 mark)

-Water -pH -Light -CO2 -Wind (speed)

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The population in trees in the forest evolved adaptations to the mountain environment. Use your knowledge of selection to explain how. (3 marks)

-Variation in original colonisers -some better adapted for survival -greater reproductive success -allele frequency change

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Name the process by which by bacteria oxidise ammonia to nitrate. (1 mark)

-Nitrification

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An increase in nitrate concentration in water entering lakes and ponds could affect algae and fish in the lake. Explain how. (3 marks)

-Algal bloom -Algae blocking light -Decomposers/saprobiotic bacteria break down dead plants -bacteria use up in respiration -fish die due to lack of O2

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Scientist were doing an experiment with pigs. Why did they use pigs with the same breed and similar genotype? (2 marks)

- Same breed so similar alleles -controls/ removes variables which will affect growth

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If the pigs were allowed to eat as much as they want how would this affect the reliability of data collected? (2 marks)

-Different growth rate/gained different amounts of biomass -not due to temperature/ the independent variable

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The efficiency of conversion of food to biomass was lower at 0*C than 20*C. Explain why. (2 marks)

-Will lose more heat/not as much energy used to maintain body temperature -heat resulting from respiration -more food used in respiration

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ATP is useful in many biological processes. Explain why (4 marks)

-releases energy in small manageable amounts -broken down in one step process -immediate source of energy -phosphorylates -lower activation energy -reformed and made again

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Describe how ATP is made in the mitochondria (6 marks)

-ATP produced in Kreb Cycle -Krebs Cycle/ link reaction produces reduces coenzyme -Electrons pass along electron transport chain -energy released -ADP/ADP+Pi -Protons move down inter membrane space -ATP synthase

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Why is it important for plants to produce ATP during respiration in addition to photosynthesis (5 marks)

-in the dark no ATP is produced -Some tissues are able to produce ATP -ATP cannot be moved from cell to cell/stored -plants use more ATP than produced -ATP for active transport -ATP for synthesis of reduced NADP

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Species that are present change during succession. Explain why. (2 marks)

-Species/plants/animals chance the environment -less hostile -species/plants better competitors

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Explain what is meant by a dominant allele (1 mark)

expressed in the phenotype

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Explain what is meant by the ecological term 'community'

all groups of all species of the population of all organisms

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What is an advantage of fish occupying different parts of the lakes (1 mark)

-Food/prey -Less/no competition

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Name the substance that combines with CO2 in chloroplast (1 mark)

RuBP

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Give 2 advantages of using a biological agent (2 marks)

-Specific -only needs one application -keeps population low -pest do not develop resistance -does not leave chemical in environment -can be used in organic farming

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Experiment carried out at the same temperature. Explain why (2 marks)

-Affects enzymes, respiration, volume or reading

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Suggest how land use could lead to a change in biodiversity (2 marks)

-removes species -removes habitats -removes variety of food sources

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Explain how farming practices the increase the productivity by agriculture crops (5 marks)

-Fertilisers added to soil to add proteins -pestisides/biological control -pesticides/weed killers -selective breeding -glass/green house enhance(CO2 light temp) -ploughing -benefit of crop rotation -protection of crops

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Describe how the action of microorganisms in soil produces a source of nitrates for crop plants (5 marks)

-proteins/amino acids -saprobionts -ammonia to nitrite -nitrite into nitrate -nitrifying bacteria -nitrogen into ammonia -by nitrogen fixing bacteria

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Explain how the use of pesticides can result in resistant strains of insect plant (5 marks)

-variation -due to mutation -allele for resistance -reference to selection -pests with resistance reproductive success -increase in frequency of allele

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What process from ammonium ions to nitrite ions? (1 mark)

-nitrification

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whats the process from nitrate ions to nitrogen (1 mark)

-denitrification

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Applying very high conc of fertilisers to the soil can reduce plant growth. Use your knowledge to explain why (2 marks)

-Soil root has lower water potential -osmosis from plants

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name two factors that can decrease death rate in a human population (2 marks)

-improved nutrition -medical care -more food - less disease -living conditions -better sanitation

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give two conditions for results from mark release and recapture to be valid ( 2 marks)

-marking not removed -no immigration or emigration -sufficient time for first sample to evenly distribute themselves -no births and deaths -sampling method is the same

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two advantages of carrying out investigation in natural habitats (2 marks)

-can see effect on biotic factors and other organisms -can see affect on abiotic factors

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describe what happens during the light dependent reaction (5 marks)

-chlorophyll absorb light energy -excies electrons -electrons move along transfer chain -energy used to join ADP and Pi -Photolysis produces electrons and oxygen -NADP reduced by electrons

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Describe the reasons for low efficiency of energy transfer through an ecosystem (5 marks)

-some light is reflected/not appropriate wavelength -some light misses -heat loss -energy loss via respiration -loss via faeces -excretion

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it has been said new species of grass may evolve over grass which have been sprayed with copper. Explain why (5 marks)

-variation -mutation -some plants have allele to live in high conc of copper -reproductive success -increase in allele -change in allele frequency -not interbreeding/separate gene pool

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What information is needed to calculate the growth rate of a population? (2 marks)

-Birth rate and Death in a given time

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scientist use percentage cover rather than frequency to record the abundance of algae present. Suggest why? (1 mark)

-difficult to count/too many to count/ too small/ grows in clumps

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Describe and explain succession (4 marks)

-pioneer species -species changing conditions of environment no longer hostile -named species better competitor out compete pioneer -first species decreases in population

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What is meant by the phenotype? (2 marks)

-expressed/appearance due to environment or alleles

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Explain why glucose is not used as a respiratory substrate in mitochondria (2 marks)

Glucose is used/ broken down in cytoplasm -glucose can not pass/cross membrane as it is too large

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Why is high level of CO2 used in an experiment of plant respiration (1 mark)

-so it is not a limiting factor

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Explain how high diversity of bird species has developed in the Amazonian forest. (5marks)

-no interbreeding/geographical isolation -mutation -different selection pressures -adapted to environment -change in allele frequency -gene pools are separate

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Speciation is less frequent in rain forest, explain a reason for this. (1 mark)

-similar/same environmental/abiotic and biotic factors/ no isolation/ gene flow can occur

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Explain the importance of collecting large amounts of data (1 mark)

-reliable representative data for a statistical tests

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Explain the advantages of using an integrated system to control agriculture pests (6 marks)

-biological agents only need one application -maintains low population -pest do not develop resistance -chemicals are used less -chemical acts quickly -can apply to specific area -kills all pests

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nitrate fertilisers applied to crops may enter ponds. Explain how nitrate may cause the death of fish in water (5 marks)

-algaie bloom blocks light -no photosynthesis without light -saprobiotic microorganisms -aerobically respire -less O2 for fishes

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Explain how intensive rearing and domestic livestock increases net productivity (4 marks)

-slaughtered when still young/ growing -fed on concentrate diet -movement restricted less respiratory loses -heating kept warm to maintain body temperature -genetically selected

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Two differenced in human population in 1970 and 2010 (2 marks)

-higher mean/average number of children -higher life expectancy in 2010 -greater life expectancy in 2010

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suggest two reasons why (2 marks)

-better medical care -better diet -sanitation -contraceptive -war

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Give a biological chemical that contains nitrogen and phosphorus (2 marks)

Amino acids and DNA

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Describe the role of microorganisms in producing nitrates from the remains of dead organisms (3 marks)

-Saprobiotic micro break down dead remains -ammonia into nitrite by nitrifying bacteria

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Explain how the increase of diversity of birds occurred in the woodland (3 marks)

-greater variety of plants - more food sources -more niches

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Give two factors that affects the rate of photosynthesis (1 marks)

Temperature and CO2

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Advantage of presenting results in a table (2 marks)

-allows comparison -number/size of sample may vary

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Respiration produces more ATP per molecule of glucose in the presence of oxygen that it does when oxygen is absent. Explain why. (2 marks)

-Oxygen in final terminal acceptor in the electron transport chain -oxidative phosphorylation -only glycolysis occurs in the presence of oxygen

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Why did the scientist use a control? (1 mark)

-to compare effect without independent variable to see if other factors have influence

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During the light independent reaction, CO2 is converted into an organic substance, describe how. (6 marks)

-CO2 + RuBP -Produces 2 3GP -sing reduced NADP -using energy from ATP -TP converted into organic substance

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Explain how human activities has contributed into global warming (4 marks)

-CO2 is a greenhouse gas -Deforestation -Combustion produces CO2 -Methane is a greenhouse gas

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Biology Unit 4 Past paper questions 2010-2014

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