An in-depth set of notes for the Topic Evolution in the GCSE AQA BIOLOGY HIGHER specification, containing the topics: fossilisation, selective breeding, cloning, adult cell cloning, speciation, natural/artifical selection, classification, variation. Grade 9 Set of notes, 15 people achieved grade 9 ...
Variation, Evolution and Genetic Engineering
Variation
Variation – the differences in characteristics of individuals in a population
Variation can be due to differences in the genes inherited (genetic causes), the
conditions in which organisms develop (environment) or a combination of both
genes and the environment
Natural selection
1) Variation due to random mutation
2) This allows the mutated species to adapt
3) This allows mutated species to survive and thrive in new conditions (survival of
the fittest)
4) This allows the mutated species to reproduce
5) This allows them to pass on their alleles containing the mutation
6) This occurs over many generations
Speciation
1) Ancestral population of species inbreeds
2) Population separated by (natural) barrier (travelled on leaf rafts)
3) These two populations can no longer interbreed
4) On each side of the barrier, the environment and therefore the random
mutations are different
5) Natural selection occurs on both sides of the barrier
6) Over an exceptionally long time, the two groups become more different as they
reproduce
7) If the barrier is removed, the two groups are reunited – however, they are too
different to breed and therefore have become two distinct species
Artificial Selection and Selective Breeding
1) Identify the desirable characteristics
2) Measure organisms and select the individuals that best display these
3) Reproductively isolate these organisms
4) Breed them together
5) From offspring, identify the most desirable
6) Inbreed the offspring
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