18.5 isolation and speciation

Question 1

What is speciation

Answer 1

Evolution of new species from existing ones

Question 2

Definition of species

Answer 2

Group of individuals that have common ancestry
So share the same genes but different alleles
Are capable of breeding with one another to produce fertile offspring
(Species reproductively separated from other species)

Question 3

Adaptive radiation

Answer 3

The Different phenotypes each combination of alleles produces
Are subject to selection pressure
Leads to each population becoming adapted to its local environment

Question 4

What does adaptive radiation lead to

Answer 4

Changes to allelic frequency of each population

Question 5

Why does genetic drift take place in small populations

Answer 5

Smaller variety of alleles in population
Genetic diversity is less
Genetic diversity restricted to the few alleles in original population
Small number of alleles not an equal chance of them being passed on
Those passed in quickly affect the whole population as their frequency is high
Any mutation to one of these alleles that is selectivley favoured will more quickly affect the whole population because it’s frequency will be high
Effects of genetic drift greater
Population change relatively rapidly
More likely to develope into separate species

Question 6

Why is genetic drift less likely to take place in large population

Answer 6

Effect of mutant allele diluted
Frequency fat less in the larger gene pool
Effects of genetic drift less and development into new species is slower

Question 7

Most important way in which new species are formed

Answer 7

Through reproductive separation followed by genetic change due to natural selection

Question 8

Describe Allopathic speciation

Answer 8

where two populations become reproductively isolated because they are geographically separated so unable to interbreed
Physical Barriers such as oceans, mountains

Environmental conditions either side of barrier vary
Natural selection influence 2 populations differently
Each evolve leading to adaptations to local conditions
Eventually can lead to formation of separate species

Question 9

Describe sympatric speciation

Answer 9

population in the same area become reproductively isolated for other reasons
E.g Mutations or different breeding seasons which do not overlap