What is a species?
- Group of similar organisms / organisms with similar features / / organisms with same genes / chromosomes;
- Reproduce to produce fertile offspring;
Explain what is meant by a heirarchy
- Groups within groups;
- No overlap (between groups);
Explain what is meant by a phylogenetic group
Grouped according to evolutionary links/history/relationships / common ancestry;
Explain what is meant by genetic
diversity
Difference in DNA/base sequence/alleles/genes;
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 (2)
- Also measures number of individuals in a species / different proportions of species;
- Some species may be present in low/high numbers;
What is meant by species richness
The number of different species in a community
Explain how natural selection produces changes within a species (6)
- Variation [caused by mutation] between members of population / species;
- Predation / disease / competition results in differential survival;
- Some have adaptations that favour survival;
- Differential reproductive success / survive to reproduce/ have more offspring/
- Pass on their advantageous alleles /
- Changes allelic frequencies
Describe how comparisons of biological molecules in two species could be used to find out if they are closely related (6)
**Genetic variation:
**
1. Compare DNA base sequence;
2. Compare RNA base sequence;
3. Compare sequence of amino acids /primary structure (of named / same protein);
4. DNA hybridisation by separating DNA strands / break hydrogen bonds;
5. Mix DNA/strands (of different species);
6. Temperature/heat required to separate (hybrid) strands indicates relationship;
OR
- Inject (seahorse) protein/serum into animal
- Obtain antibodies/serum;
- Add protein/serum/plasma from other (seahorse) species
- Amount of precipitate indicates relationship;
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 (3)
- 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
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)
- Mark for general principle of - reduced variety/number of different alleles/DNA / reduced gene pool (in new population);
- Founder effect;
- A few individuals from a population become isolated/form colonies:
- (Genetic) bottlenecks;
- (Significant) fall in size of population
- Selective breeding / artificial selection;
- Using organisms with particular alleles / traits / phenotypes / characteristics
Scientists can use protein structure to investigate the evolutionary relationships
between different species.
Explain why (3)
- Amino acid sequences / primary structure;
- Closer the (amino acid) sequence the closer the relationship;
- (Protein structure) related to (DNA) base/triplet sequence;
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)
- Decrease in variety of plants / fewer plant species;
- Fewer habitats/niches;
- Decrease in variety of food / fewer food sources;
- Aspect of clearing forest (killing insects) eg machinery, pesticides;
What is meant by a genetic bottleneck (2)
- Sudden decrease in population / many killed by an event eg earthquake;
- Idea of reduced/low genetic variation/diversity / reduction in (variety of) alleles / smaller gene pool;
Suggest one ethical argument for maintaining biodiversity
Prevent extinction /loss of populations/ reduction in populations /loss of habitats / save organisms for future generations
Suggest one economic argument for maintaining biodiversity (4)
- medical / pharmaceutical uses;
- commercial products / example given;
- tourism;
- agriculture;
- saving local forest communities;
Farmers clear tropical forest and grow crops instead. Explain how this causes the diversity of insects in the area to decrease (5)
- Lower diversity of plants/ few species of plants/less variety of plants/few plant layers;
- Few sources/types of food/feeding sites;
- Few habitats/ niches;
- Fewer (species of) herbivore so few (species of) carnivores;
- Aspect of agriculture (killing insects);
Describe how courtship behaviour increases the probability of successful mating (5)
- Attracts/recognises same species;
- Attracts/recognises mate/opposite sex;
- Indication of sexual maturity/ fertility / synchronises mating;
- Stimulates release of gametes;
- Form pair bond;
