4. evolution by natural selection

Question 1

define variation

Answer 1

the differences which exist between individuals in a population, due to genetic variations and producing different phenotypes

Question 2

give two causes of genetic variation

Answer 2

1. environmental
2. genetic

Question 3

outline environmental causation behind variation

Answer 3

• climate change
• availability of food or water
• intensity of light

Question 4

outline genetic as a causation

Answer 4

• mutations: result in genetic variation in chromosomes
• meiosis: independent segregation or crossing over
• fertilisation of gametes: random, new combination of genes produced by chance

Question 5

what is genetic diversity determined by?

Answer 5

the total number of different alleles

Question 6

what process drives evolution?

Answer 6

natural selection

Question 7

define natural selection

Answer 7

where reproduction leads to certain genetics being inherited, which are more suitable to the environemnt, as a result of selective pressures

Question 8

what are selective pressures

Answer 8

factors which can affect the survival of an organism and reproductive success
(comptition, food, water, space)

Question 9

outline natural selection as a drive for evolution

Answer 9

1. variation in a population
2. due to mutations, some individuals have favourable alleles which increase their chance of survival and therefore reproduction
3. they pass on favourable alleles to offspring, increasing the allele frequency
4. if no interbreeding occurs, speciation can occur

Question 10

what is geographical isolation

Answer 10

where populations are seperated by a physical barrier so no interbreeding can occur