17: Selection + Evolution Flashcards
1
Q
What is meant by the term species?
A
- group of organisms with similar physiological, biochemical, behavioural and morphological features
- which can interbreed to produce fertile offspring
- reproductively isolated from other species
2
Q
How might speciation occur?
A
- allopatric speciation = geographically isolated
- no gene flow between populations = seperate gene pools = genetically isolated
- point of genetic change = mutations, only way to get new alleles
- different allele frequency, different chromosome numbers = genetic drift
- different selection pressures in each location, which further changes the allele frequency of the population because different selection pressures will favour different/certain alleles
- over time, few alleles in each location will be prevalent and the changes in each population to the extent where they cant be recognised as the same species anymore
- the 2 populations eventually wouldn’t be able to reproduce to make fertile offspring, wouldn’t even mate potentially
- reproductively isolated, no breeding between them
- in each location, the organisms which do not possess these favourable alleles will not be fit enough to survive and reproduce, so those unfavourable genes won’t continue in the population
3
Q
What is allopatric speciation?
A
4
Q
What is sympatric speciation?
A
5
Q
What is stabilising selection?
A
eliminates the extremities
6
Q
Factors affecting animal distribution?
A
- Food availability
- Territory
- temperature
- water
- breeding sites
7
Q
Factors affecting plant distribution?
A
- soil pH
- soil salinity
- nutrient availability
- temperature
- water
- light
8
Q
What is the difference betwene allopatric and sympatric speciation?
A
allopatric - due to geographical isolation
sympatric - in the same area but different isolating mechanisms
