3.4.6 - BIODIVERSITY WITHIN A COMMUNITY

Question 1

a forest was cleared to make more land available for agriculture.

after the forest was cleared the species diversity of insects in the area decreased. explain why (3)

Answer 1

1. decrease in the variety of plants/fewer plant species
2. fewer habitats
3. decrease in variety of food/fewer food sources

Question 2

explain why it is more useful to calculate an index of diversity than to record species richness (2)

Answer 2

1. index of diversity also measures number of each species
2. so it is useful because there may be few of other species

Question 3

give one way in which sampling procedure could be standardised (1)

Answer 3

any one:

1. same size net
2. same sampling time
3. same size of area
4. samples taken at the same time of the day

Question 4

what data would the students need to collect to calculate their index of diversity in each habitat? (1)

Answer 4

number of species and number of individuals of each species

Question 5

give two ways in which the students would have ensured their index of diversity was representative of each habitat (2)

Answer 5

1. random samples
2. large number of samples

Question 6

farmers are now being encouraged to replant hedges on their land

suggest and explain one advantage and one disadvantage to a farmer of replanting hedges on their farmland (2)

Answer 6

advantages:
1. greater biodiversity so increase in predators of pests
2. increase in predators of pests so more yield/less damage to crops
3. increase in pollinators so more yield/income

disadvantages:
1. reduced land area for crop growth
2. greater biodiversity so increased pest population
3. increased pest population so less yield

Question 7

what is meant by species richness? (1)

Answer 7

a measure of the number of different species in a community

Question 8

the scientists collected bees using a method that was ethical and allowed them to identify accurately the species to which each belonged

in each case, suggest one consideration the scientists had to take into consideration to ensure their method was ethical and that allowed them to identify accurately the species to which each belonged (2)

Answer 8

1. must not harm the bees
2. close examination

Question 9

what is a species? (1)

Answer 9

a group of organisms that are able to produce fertile offspring

Question 10

outline a method ecologists could use to determine the plant species richness at one site (3)

Answer 10

1. a method of selecting sampling sites at random
2. use of a quadrat
3. identify plant species/count the number of different plant species in each quadrat

Question 11

the index of diversity of the insects was higher in the hedge than in the barley field. suggest why (3)

Answer 11

1. more plant species
2. more food sources/variety of food
3. more habitats

Question 12

the UK government pays farmers to leave grassy strips around the edges of fields of crops. these grassy strips contains a variety of plant species. leaving the strips is an attempt to encourage biodiversity of animals.

give two reasons why the grassy strips increase the biodiversity of animals (2)

Answer 12

any two:

1. increase in plant diversity leads to more types of food for animals
2. increase in variety of animals leads to increase in predator species
3. increase in habitat

Question 13

describe how you would investigate the effect of an invasion by a non-native species of plant (a biotic environmental factor) over many years on the abundance of a native species of plant in a community. (3)

Answer 13

1. set up a grid system with coordinates
2. place large number of quadrats selected at random
3. count number of/estimate percentage cover of native plant species in the quadrats
4. repeat at the same time each year for many years

Question 14

suggest how a student would obtain data to give a more precise value for the index of diversity of a habitat (2)

Answer 14

1. take more samples and find mean
2. method for randomised samples described

Question 15

suggest the advantage of using fluorescent powder to mark the insects (2)

Answer 15

ONE PAIR

1. only glows brightly with UV
2. so doesn’t increase predation

OR

1. glows brightly with UV
2. makes it easier to pick out labelled insects

Question 16

what two measurements are needed to calculate an index of diversity? (2)

Answer 16

1. number of individuals of each species
2. total number of species (species richness)

Question 17

speciation is far less frequent in the reformed Amazonian forest. suggest one reason for this (1)

Answer 17

same environment

Question 18

scientists have produced a mutated rice variety in which there is no crossing over.

a population of the mutant rice variety produced by sexual reproduction shows genetic variation. populations of non-mutant rice varieties also show genetic variation.

suggest and explain the similarities and differences in the causes of genetic variation within these rice populations (3)

Answer 18

similarities:
1. both populations have variation due to independent segregation/assortment of chromosomes
2. both populations have variation due to random fertilisation of gametes
3. both populations have further mutations

differences:
1. crossing over only causes variation in non-mutant population

Question 19

mammals feed their young on milk. CEL digests the triglycerides in milk. the ability to produce CEL occurred due to a gene mutation.

describe how natural selection may have led to all mammals in a population producing CEL (4)

Answer 19

1. mutation results in a new allele
2. those with the new allele are able to digest milk/triglycerides
3. individuals with CEL/allele more likely to survive and reproduce
4. directional selection
5. increase in frequency of this allele in population

Question 21

in Africa today, most of the human population are resistant to malaria caused by P. vivacious

use your knowledge of natural selection to explain why this resistance is so common in Africa (4)

Answer 21

1. mutation produced (resistant) allele
2. those with allele/resistance less likely to/do not get malaria OR those with allele/resistance survive
3. so more likely to reproduce and pass on the allele
4. over generations allele frequency increases