Biodiversity And Classification

Question 1

What is a species?

Answer 1

1. Group of similar organisms / organisms with similar features / / organisms with same genes / chromosomes;
2. Reproduce to produce fertile offspring;

Question 2

Explain what is meant by a heirarchy

Answer 2

1. Groups within groups;
2. No overlap (between groups);

Question 3

Explain what is meant by a phylogenetic group

Answer 3

(Grouped according to) evolutionary links/history/relationships / common ancestry;

Question 4

Explain what is meant by genetic
diversity

Answer 4

Difference in DNA/base sequence/alleles/genes;

Question 5

The number of species present is one way to measure biodiversity. Explain why an
index of diversity may be a more useful measure of biodiversity.

Answer 5

Also measures number of individuals in a species / different proportions of species;
Some species may be present in low/high numbers;

Question 6

What is meant by species richness

Answer 6

The number of different species in a community

Question 7

Explain how natural selection produces changes within a species.

Answer 7

Variation [caused by mutation] between members of population / species;
2. Predation / disease / competition results in differential survival;
3. Some have adaptations that favour survival;
4. Differential reproductive success / survive to reproduce/ have more offspring/
4. Pass on their advantageous alleles /
5. Changes allelic frequencies

Question 8

Describe how comparisons of biological molecules in two species could be used to find out if they are closely related.

Answer 8

Genetic variation:
Compare DNA base sequence;
Compare RNA base sequence;
Compare sequence of amino acids /primary structure (of named / same protein);

DNA hybridisation by separating DNA strands / break hydrogen bonds;
Mix DNA/strands (of different species);
Temperature/heat required to separate (hybrid) strands indicates relationship;

Immunological evidence – not a mark
Inject (seahorse) protein/serum into animal;
(Obtain) antibodies/serum;
Add protein/serum/plasma from other (seahorse) species;
Amount of precipitate indicates relationship;

Question 9

In classification, comparing the base sequence of a gene provides more information than comparing the amino acid sequence for which the gene codes. Explain why.

Answer 9

• Reference to base triplet/triplet code / more bases than amino acids / longer base sequence than amino acid sequence;
• Introns/non-coding DNA;
• Same amino acid may be coded for / DNA code is degenerate;

Question 10

Scientists’ analysis of blood proteins has indicated a lack of genetic diversity in populations of some organisms.

Describe the processes that lead to a reduction in the genetic diversity of populations of organisms. (6)

Answer 10

1. Mark for general principle of - reduced variety/number of different alleles/DNA / reduced gene pool (in new population);
2. Founder effect;
3. A few individuals from a population become isolated/form colonies:
4. (Genetic) bottlenecks;
5. (Significant) fall in size of population
6. Selective breeding / artificial selection;
7. Using organisms with particular alleles / traits / phenotypes / characteristics

Question 11

Scientists can use protein structure to investigate the evolutionary relationships
between different species.

Explain why.

Answer 11

1. Amino acid sequences / primary structure;
2. Closer the (amino acid) sequence the closer the relationship;
3. (Protein structure) related to (DNA) base/triplet sequence;

Question 12

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. (4)

Answer 12

1. Decrease in variety of plants / fewer plant species;
2. Fewer habitats/niches;
3. Decrease in variety of food / fewer food sources;
4. Aspect of clearing forest (killing insects) eg machinery, pesticides;

Question 13

What is meant by a genetic bottleneck.

Answer 13

1. Sudden decrease in population / many killed by an event eg earthquake;
2. Idea of reduced/low genetic variation/diversity / reduction in (variety of) alleles / smaller gene pool;

Question 14

Suggest one ethical argument for maintaining biodiversity.

Answer 14

Prevent extinction /loss of populations/ reduction in populations /loss of habitats / save organisms for future generations (idea of);

Question 15

Suggest 4 economic argument for maintaining biodiversity.

Answer 15

A suitable example of how some species may be important financially e.g.
1. medical / pharmaceutical uses;
2. commercial products / example given;
3. tourism;
4. agriculture;
5. saving local forest communities;

Question 16

Farmers clear tropical forest and grow crops instead. Explain how this causes the
diversity of insects in the area to decrease.

Answer 16

Lower diversity of plants/ few species of plants/less variety of plants/few plant layers;
2. Few sources/types of food/feeding sites;
3. Few habitats/ niches;
4. Fewer (species of) herbivore so few (species of) carnivores;
5. Aspect of agriculture (killing insects);

Question 17

Describe how courtship behaviour increases the probability of successful mating.

Answer 17

1. Attracts/recognises same species;
2. Attracts/recognises mate/opposite sex;
3. Indication of sexual maturity/ fertility / synchronises mating;
4. Stimulates release of gametes;
5. Form pair bond;

Question 18

Give two pieces of information needed to calculate an index of diversity for a community.

Answer 18

Number of (organisms of) each species;
Accept: ‘population’ for number and accept individual for organism.
Accept: ‘species richness’
Total number of organisms (of all species) / Total number of species;

Question 19

What is meant by species diversity?
__________________________________________

Answer 19

Number of species in a community;
Accept: number of species in a habitat/area/ecosystem

Question 20

A scientist investigated the effect sewage entering a river had on the distribution of
organisms living in the river. Where sewage entered the river, he found a high density of
organisms but a low index of diversity.
Suggest how sewage entering the river could explain the scientist’s findings (3)

Answer 20

Described effect of sewage (eg oxygen depletion/is toxic/kills);
Accept: increase in BOD
Accept: eutrophication/description of eutrophication
Prevents some/many species colonising/ reproducing/remaining;
Accept: only a few species survive
Sewage is food source for (individuals of) some/a few/species;
(So) increase only in their numbers;

Question 21

Suggest the additional steps that should be taken by the scientists before they are
able to make any conclusions about the effect of sewage entering this river.
______________________________________________________________

Answer 21

Do repeats to find a pattern/distribution/mean (of index of diversity)

Question 22

A second scientist repeated the investigation of the first scientist at the same place. The
second scientist obtained a high index of diversity.
(i) Explain how the second set of results affects the ability of the scientists to make any
conclusions about the effect of sewage on the index of diversity

Answer 22

Results are not repeatable / are not representative / unreliable / conflict / contradict

Question 23

e UK government pays farmers to leave grassy strips around the edges of fields of crops.
These grassy strips contain a variety of plant species. Leaving the strips is an attempt to
encourage biodiversity of animals.
(a) Give two reasons why the grassy strips increase the biodiversity of animals.

Answer 23

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 niche / habitat

Question 24

A group of scientists investigated the effect of grassy strips on the biodiversity of soil animals
The scientists decided to collect animals from the soil samples for 40 minutes.
Suggest how the scientists decided that 40 minutes was an appropriate time.
________________________________________________________________

Answer 24

Repeat soil sorting for different times and record number of species collected;
2. Find optimum time / time beyond which further sorting does not lead to increase in animal species found

Question 25

What is meant by ‘species richness’?
____________________________________

Answer 25

measure of) the number of (different) species in a community;
For ‘community’ accept ‘habitat/ecosystem/one area/environment’
Reject ‘in a population

Question 26

Suggest how the scientist measured the rate of water flow in the river.
_______________________________________________________________

Answer 26

Movement of (floating) object over known distance and over given time OR
Time to fill container of known volume
OR
Use of data logging device;
Accept: digital device eg (digital) flow meter

Question 27

Give two ways the students would have ensured their index of diversity was
representative of each habitat.
1 ________________________

Answer 27

Random samples;
Large number (of samples)
OR
(Continue sampling) until stable running mean;
Both marks can be awarded on one line.
Ignore other answers unless they contradict mark points.

Question 28

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 her farmland.

Answer 28

Adv:
Greater (bio)diversity so increase in predators of pests
OR
Increase in predators of pests so more yield/income/less pesticides/less damage to crops
OR
Increase in pollinators so more yield/income
OR
May attract more tourists/subsidies to their farm so more income (from diversification);
Dis:
Reduced land area for crop growth/income
OR
Greater (bio)diversity so increase pest population OR
Increase pest population so less yield/less income/(more) need for pesticides/(more) damage to crops
OR
Increased (interspecific) competition so less yield/income
OR
More difficult to farm so less income;

Question 29

Scientists investigated the genetic diversity between several species of sweet potato.
They studied non-coding multiple repeats of base sequences.
Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats
are positioned in the genome. 2

Answer 29

1.DNA that does not code for protein/polypeptides
OR
DNA that does not code for (sequences of) amino acids OR
DNA that does not code for tRNA/rRNA;
2. Positioned) between genes;
Reject (positioned) ‘in introns’ or ‘between exons’.