d4.1 natural selection

Question 1

why does there need to be a selection pressure

Answer 1

population always tend to produce more than the environment can support

Question 2

struggle for survival [4]

Answer 2

1. food
2. predation
3. parasitism
4. disease

Question 3

biotic factors [3]

Answer 3

1. struggle survival
2. competition for mates
3. competition for space

Question 4

what is population dependent on

Answer 4

selection pressures

Question 5

abiotic factors

Answer 5

population independent

Question 6

abiotic factor eg

Answer 6

temperature

Question 7

how to get variation between number of species

Answer 7

1. random mutation
2. sexual reproduction

Question 8

how does variation occur during random mutation [2]

Answer 8

1. dna replication
2. viral infection

Question 9

mate selection

Answer 9

females of some species will select male mates on an exaggerated trait

Question 9

how does variation occur in sexual reproduction [2]

Answer 9

1. meiosis- crossing over (prophase i) and random assortment of chromosomes (metaphase i)
2. random fertilisaiton

Question 10

mate selection eg

Answer 10

peacocks

Question 10

how does mate selection affect their traits

Answer 10

the exaggerated traits will become more exaggerated until it hinders their survival

Question 11

gene pod

Answer 11

consists of all the gene and their alleles present in a population

Question 12

allele frequency eg

Answer 12

alcohol dehydrogenase breaks down alcohol in the liver- linked with rice cultivation and sake production

Question 13

Weismann’s germ plasm theory

Answer 13

natural selection drives allele frequency changes in a gene pool

Question 14

what gets passed on according to the germ plasm theory

Answer 14

germ plasm
things in the somatic cells dont get passed on

Question 15

3 types of natural selection

Answer 15

1. directional selection
2. stabilising selection
3. disruptive selection

Question 16

directional selection

Answer 16

individuals that display a more extreme of a trait have greater fitness than individuals with an average form of the trait

Question 17

directional selection change in shape

Answer 17

change mean to left or right

Question 18

natural selection distribution

Answer 18

normal distribution- most in normal range

Question 19

directional selection eg

Answer 19

beak of gallapagos

Question 20

stabilising selection

Answer 20

individuals with the average form of a trait have the highest fitness
- wont survive with too little or too much

Question 21

stabilising selection change in shape

Answer 21

higher in the middle
narrower than normal distribution

Question 22

disruptive selection

Answer 22

individuals with either extreme variation of a trait have a greater fitness than individuals with the average form of the trait

Question 23

disruptive selection eg

Answer 23

salmon
hooknoses- bigger so can fight
jack- small so can sneak in

Question 24

disruptive selection change in shape

Answer 24

mean decrease
‘m’ shape

Question 25

hardy-weinburg equilibrium

Answer 25

used to determine if a population is in genetic equilibrium

Question 26

hardy-weinberg conditions that must be maintained for a population to be in genetic equilibrium [5]

Answer 26

1. no mutation in gene
2. mating is random
3. no immigration or emigration
4. population is large enough to prevent allele frequencies changing due to change
5. natural selection does not favour one phenotype over another

Question 27

why is the condition no mutation

Answer 27

so alleles are not changed and no new alleles are being generated

Question 28

why does mating need to be random

Answer 28

no phenotype preferentially mates with another particular phenotype

Question 29

why can there be no immigration or emigration

Answer 29

constant allele frequencies