variation and selection

Question 1

Variation (different phenotypes)

Answer 1

1. main source is a mutation
2. also as a result of meiosis
3. can be caused by environment
4. most is caused by combo of genetic and environmental factors
5. only genetic variation results in evolution

Question 2

how does natural selection work (a type of evolution)

Answer 2

1. variation of individuals of same species (different alleles)
2. predation, disease, competition (selection pressures) cause struggle for survival
3. different levels of survival and reproductive successs in a population
4. individuals with a phenotype that increase chance of survival more likely to survive reproduce and pass on genes
5. greater proportion of next generation inherit beneficial alleles.
6. frequency of beneficial alleles in gene pool increases from generation to generation

Question 3

stabilising selection

Answer 3

individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
occurs when environment isnt changing
reduces range of possible phenotypes

Question 4

directional selection

Answer 4

individuals with alleles for a single extreme phenotype are more likely to survive and reproduce
could be due to environmental change

Question 5

disruptive selection

Answer 5

individuals with alleles for extreme phenotypes at either end of the range more likely to survive and reproduce
opposite to stabilizing as characteristics in middle lost
occurs when environment favour more than one phenotype