genetic diversity and mutation

Question 1

suggest two reasons why not all solar energy can be used in photosynthesis.

Answer 1

light misses plant/leaf/chloroplast/
wrong wavelength of light
limiting factors

Question 2

describe one way in which energy is lost from the first trophic level

Answer 2

metabolism/respiration/decay

Question 3

suggest one reason why the loss of energy from the first trophic level is greater than the second

Answer 3

greater biomass in the first trophic level

Question 4

explain the meanings of community and population

Answer 4

community- all organisms living in a particular place
population- all organisms in one particular species

Question 5

describe how you could use point quadrats to investigate the distribution of plants at lake side

Answer 5

transect from water onto bank;
point quadrat frame placed at regular intervals;
record species touching points;
calculate percentage/process with kite diagram/use statistical test to show..

Question 6

give two reasons why the mark-release-recapture technique would not give a reliable estimate of the blue tit population in a wood between April and June

Answer 6

as breeding season many new birds being added to population;
birds do not mix at random as they are in territories;

Question 7

suggest how the population of adult blue tits in a wood might be estimated between April and June.

Answer 7

capture markl and recapture

Question 8

suggest how the addition of organic matter to water in an accidental discharge of farmyard waste may result in a lack of oxygen

Answer 8

decomposition/breakdown of organic material/decomposers;
bacteria;
oxygen used in bacterial respiration;

Question 9

suggest how the addition of organic matter to water in an accidental discharge of farmyard waste may result in an increase in nitrates

Answer 9

organic material broken down to ammonia;
nitrifying bacteria;
convert ammonia to nitrite;

Question 10

describe how the mark-release-recapture method could be used to estimate the population of mice in the area being studied. What assumptions would you have to make in using this method?

Answer 10

Detail of one of the following
Method of trapping,Method of marking;
Collection of full range of data/Number marked/Number recaptured/Number of unmarked animals/total in second sample;
Correct method of calculating results;P= )(221MNxNNPopulation is stable between first and second sampling;
Random mixing of marked animals in population;
Trapping/marking has no adverse effect on mice;

Question 11

part from the number of species, give one other piece of information needed to calculate the diversity index

Answer 11

number of individuals of each species

Question 12

explain what is meant by a transect

Answer 12

a line / belt across a habitat / field / environment

Question 13

explain how waterlogging of the soil might affect the rate of growth of a seedling

Answer 13

low oxygen content in soil / around roots / anaerobic conditions;
reduced (active) uptake of ions for growth/ root development inhibited, or more denitrification, so less nitrate for growth.

Question 14

explain what is meant by ‘niche’

Answer 14

the set of conditions (in a habitat) that an organism requires, or the role(s) of a species in a community / ecosystem / environment

Question 15

suggest why the ecosystem supports ‘relatively few species’

Answer 15

low diversity in / few species adapted for extreme environments;
because extreme factors/named example make conditions unsuitable

Question 16

sundew plants are able to digest insects trapped on their leaves. Explain how this is of benefit to the sundews in this environment

Answer 16

extinction of rare species / species adapted to this environment;
potential uses of ‘lost’ species;
possible effects on food webs / ecosystem, e.g. greenshanks can’t breed;
aesthetic aspects / loss of tourists;
low economic value of timber / trees don’t grow well;

Question 17

using one example of each to illustrate your answer, explain the difference between density dependent and density independent factors

Answer 17

example of density dependent factor, e.g. food, space, disease;
example of density independent factor, e.g. light, temperature(reject: weather, climate);
density dependent factors depend on / affected by size of population;
density independent factors affect organisms whatever the population size,or, examples used to explain, e.g. increasing competition for food

Question 18

explain what is meant by a density dependent factor

Answer 18

factor whose effect changes according to population size

Question 19

the pond contains a population of water beetles. The beetles are about 1.5 cm long. Describe one way in which the size of the beetle population could be estimated

Answer 19

catch sample of beetles by netting;Mark and release and recapture;
use proportion recaptured to calculate population size / give correct Lincoln index formula to be used;

Question 20

in a deep lake, only plants that float near the surface can survive. They depend on a supply of mineral nutrients from decomposing matter at the bottom of the lake. The temperature at the bottom of the lake stays almost constant. Explain how differences in the temperature of the water nearer the surface can affect the supply of nutrients from the bottom of the lake

Answer 20

Warm water forms layer on cold / stratification;
preventing circulation of nutrients;
or cooling of surface water / thermocline broken down;
sets up circulation of nutrients / convection currents;

Question 21

in creeping buttercup, the offspring produced from seeds produced by sexual reproduction have a shorter mean life span than the offspring produced asexually. Suggest two explanations for the shorter mean life span of sexually reproduced buttercup plants.

Answer 21

smaller/at earlier stage of development/ less well established so not able to withstand being eaten by animals;
dispersed to unsuitable ground;
unable to compete with faster growing asexual offspring/not supplied by parent until established;

Question 22

describe how you would place quadrats so as to achieve a random distribution.

Answer 22

grid;
selection of coordinates usingrandom number tables/ numbers from a hat

Question 23

using informationin the table and your own knowledge, explain why the nitrate concentration is greater at position C than at position A.

Answer 23

dead plant material /humus is converted to nitrate by soil bacteria;

(one mark for principle)Plant material decomposed by saprophytes/ saprobionts;

organic molecules containing nitrogen / protein converted to ammonia;

involving ammonifying bacteria;

ammonia to nitrite;

nitrite to nitrate;

involving nitrifying bacteria;

Question 24

the mark-release-recapture technique may be used to estimate population size.Give two assumptions that must be made when using this technique

Answer 24

mixes randomly/completely in population;

marking does not have an effect/does not wear off;

no migration/emigration/immigration;no change in population size between samples/life span longer than timebetween release and recapture;

no births or deaths;

not trap-happy/trap-shy;

Question 25

Natural woodlands, which once covered 80% of Britain, are stable ecosystems with high levels of diversity. These natural woodlands were dominated by a range of species, such as oak and ash, which lose their leaves in winter. Much of today’s woodland consists of evergreen conifer plantations. Conifers are grown for timber. They are planted close together in straight lines.The trees are usually of the same age and the same species. Describe how you would obtain the necessary data to calculate the index of diversity for the tree species growing in a natural woodland.

Answer 25

grid area;method of generating coordinates;to place quadrat at random; (max 2 for sampling)number of individuals;number of eachspecies;

Question 26

explain why the diversity of animals is higher in natural woodland than in conifer plantations.

Answer 26

more light reaches the ground;more type of plant/producers; more habitats/microclimates;more varieties of food/more complex food web;more niches; different nesting sites; dead wood/leaves left to rot providing more nutrients/shelter; greater varietyof herbivore/primary consumer/carnivore;

Question 27

the conifers used in plantations are the result of a long period of selection for desirable characteristics. Explain how a programme of selection might affect the variety of alleles in a population.

Answer 27

reduces (the variety of alleles) / genetic diversity; only certain phenotypes allowed / selected to breed;(phenotypic) character controlled by allele; some/non-selected alleles eliminated/frequency decreased;others/selected alleles increase in frequency;

Question 28

describe how the investigators could obtain the value for vegetation cover in each quadrat.

Answer 28

system for subdividing quadrat into, e.g. many squares; method of estimatingcover in small squares, e.g. counting those where cover over 50%, or cover at points (of intersection);

Question 29

the correlation between vegetation cover and soil moisture content was tested statistically. These two factors were found to be positively correlated, and p \< 0.05. Explain what this result means.

Answer 29

increasing vegetation cover is related to increasing moisture content(allow ‘affects‘ moisture content or vice versa, not ‘causes); correlation is significant / not due to chance / can reject null hypothesis; only 1 in 20/5% probability that the correlation is due to chance;

Question 30

at first the waste heap had no plants growing on it. Some of the first plants to colonise it were small herbaceous plants. Explain one way in which colonisation by herbaceous plants could change the physical environment.

Answer 30

factor; and linked effect e.g.wind-blown particles trapped; accumulation of soil; OR accumulation of organic/dead/decomposed matter/humus; increase in mineral ions / improved water retention / improved soil structure; OR nitrogen fixation; increased nitrate concentration / improved soil fertility;

Question 31

use the drawing to suggest how its shape helps the penguin to maintain its core body temperature in such low air temperatures.

Answer 31

rounded shape / small head / short legs / small extremities; low surface area:volume ratio limits heat loss;

Question 32

at rest a penguin maintains a constant metabolic rate as the air temperature falls to –10 °C. Below this temperature its metabolic rate increases. Explain why the metabolic rate can stay constant down to –10 °C, but rises when the temperature falls below this.

Answer 32

insulation / physical responses prevent heat loss/maintain temperature above –10 °C ; below –10 °C heat loss greater than heat gain from respiration; rate of respiration/metabolism increased to generate heat;

Question 33

at the start of winter emperor penguins walk about 100 km from the sea to the permanent ice shelf. Here each female lays a single eggwhich the male incubates in a pouch above his feet. The females return to the sea, but the males stay at the breeding site and do not feed. Large groups, often more than a thousand birds, huddle close together. They regularly change position within the huddle. When the chicks have developed, after 100 days, their fathers walk the 100 km back to the sea so that they can feed again.When they leave the sea at the start of winter, the males weigh 35 kg and may have up to 20 kg of stored fat. Walking uses 7.5g of fat per km. Research has shown that at the average temperatures on the ice a penguin standing on its own loses 200 g of its stored fat per day. However, when in a huddle only 100 g per day is lost. explain how huddling close together helps to reduce the loss in mass from 200 g to 100 g per day.

Answer 33

reduction in exposed surface area so less heat loss; (not just: use or gain heat from each other)less fat / food store used in maintaining temperature;

Question 34

at the start of winter emperor penguins walk about 100 km from the sea to the permanent ice shelf. Here each female lays a single eggwhich the male incubates in a pouch above his feet. The females return to the sea, but the males stay at the breeding site and do not feed. Large groups, often more than a thousand birds, huddle close together. They regularly change position within the huddle. When the chicks have developed, after 100 days, their fathers walk the 100 km back to the sea so that they can feed again.When they leave the sea at the start of winter, the males weigh 35 kg and may have up to 20 kg of stored fat. Walking uses 7.5g of fat per km. Research has shown that at the average temperatures on the ice a penguin standing on its own loses 200 g of its stored fat per day. However, when in a huddle only 100 g per day is lost. use the information above to explain why the huddling behaviour is essential to the survival of the male penguins. You should include relevant calculations in your answer.

Answer 34

figures used to calculate mass of fat used: for birds that do not huddle (e.g. walking uses 100 × 7.5 = 750 g (0.75 kg) and 100 days on ice uses 20 kg = 20.75 kg); for birds that huddle only 10.75 kg used; all stored fat used in 100 days if not in huddle / insufficient fat reserve for single birds to return to sea;

Question 35

what is meant by an abiotic factor?

Answer 35

the non-living / physical part (of an ecosystem/environment);

Question 36

do abiotic factors exert a density-dependent or a density-independent effect on a population? Using an example, explain your answer.

Answer 36

density-independent, with named abiotic factor and a specific effect;

Question 37

explain the increase in the number of species of Hemiptera.

Answer 37

populations of different species; living in the same environment/habitat;(often) named after dominant plant/example;

Question 38

Answer 38

Two marks for correct answer of 3.21; One mark for incorrect answer that clearly shows understanding of ∑n(n –1);

Question 39

explain why it ismore useful to calculate the index of diversity than to record just the number of species present.

Answer 39

Measures number of individuals and number of species; some species only present in small numbers;

Question 40

In the late 18thcentury, the population of northern elephant seals was estimated to be about 150 000. These seals lived in different colonies in different places. The seals were then hunted. By 1910, the total population had fallen to under 100. All these seals lived in a single colony on one island. Hunting then stopped. Numbers increased and there are now approximately 150 000 seals living in many different colonies. Use this information to explain what is meant by a genetic bottleneck

Answer 40

Genetic bottleneck linked to low genetic diversity/smaller gene pool; reference to very low seal population/population in 1910/under100 seals/caused by hunting;