Biodiversity, species and taxonomy

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

1. 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/
5. Pass on their advantageous alleles /
6. 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 one 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

1. 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

Describe how organisms are grouped in a phylogenetic classification system

Answer 18

1. Hierarchy of groups with no overlaps
   OR smaller groups within larger groups with no overlaps
2. grouped according to evolutionary origins/relationships/history