Selection And Speciation

Question 1

How does variation arise

Answer 1

Mutation, meiosis,random fertilisation of gametes

Question 2

Natural selection

Answer 2

Variation exists in a population due to mutation
Selection pressures in environment due to biotic and abiotic factors
Better adapted individuals more lively to survive and reproduce.
More likely to pass on their alleles
Offspring now have advantageous alleles
Increase in allelic frequency over time

Question 3

Stabilising selection

Answer 3

Occurs in a population where environment is stable
selection pressure at both ends of distribution
Favours the average and eliminates the extreme
Reduces variability

Question 4

Directional selection

Answer 4

Occurs when population is not extreme
Favours an extreme
Mean will shift towards extreme

Question 5

Speciation definition

Answer 5

Evolution of a new species from existing species
Two populations must undergo a period of reproductive isolation to become genetically distinct via mutations and selection pressures

Question 6

allopatric speciation

Answer 6

Physical barrier blocks a population preventing interbreeding
Each population has its own selection pressures and mutations
Change in genotype and phenotype
When populations meet they are so different they can’t interbreed and have become their own species

Question 7

Sympatric speciation

Answer 7

Become separated by choice
Choice of foods or mates or active hibernation
Become genetically different and develop though selection to become their own species

Question 8

Genetic drift or bottle neck

Answer 8

Random increase or decrease in allelic frequency
Important in small populations where loss of individuals with certain alleles cause a significant change in the frequency of the alleles within the population

Question 9

Gene flow or founder effect

Answer 9

Change in allelic frequency due to migration of fertile individuals

Question 10

Disrupting selection

Answer 10

Opposite to stabilising
Favours both extremes
Over time 2 extremes will dominate and mean will shift in both directions
Least common type