Evolution

Question 1

what is the gene pool ?

Answer 1

range of alleles present in a population

Question 2

what is the term for how often an allele occurs in a population ?

Answer 2

allele frequency

Question 3

state what evolution is

Answer 3

change in allele frequency over time

Question 4

what is selection pressure ?

Answer 4

factor (predatation/disease/competition) that creates a struggle for survival

Question 5

what is stabilising selection ?

Answer 5

• environment is constant
• individuals w/ alleles for characteristics in middle of range more likely to survive
• reduces range of possible phenotypes

Question 6

give an example of stabilising selection

Answer 6

range of fur length:

• in stable climate, having extremes of fur length makes harder to maintain body temp
• less likely to survive…
• allele freq. of average fur length increases
• range of fur length decreases

Question 7

what is directional selection ?

Answer 7

• change in environment
• individuals w/ alleles for more extreme characteristics more likely to survive
• allele frequency shifts to one side

Question 8

give an example of directional selection

Answer 8

fur length:

• habitat becomes very cold
• those w/ long fur are more likely to survive
• over time, allele frequency of long fur increases

Question 9

what is genetic drift ?

Answer 9

alleles being passed on through generations and increasing in frequency, all based on chance

Question 10

when is genetic drift more of a cause of evolution than natural selection ?

Answer 10

in small populations, where chance has a greater influence

Question 11

what is genetic bottleneck ?

Answer 11

• event occurs, greatly reducing population
• reduction in gene pool
• allele frequency changes
• genetic drift has a greater effect

Question 12

what is the founder effect ?

Answer 12

• some individuals start new population
• by chance, most are one particular genotype
• new pop. will grow w/ reduced genetic variation
• more heavily influenced by genetic drift as is small pop.

Question 13

what does the Hardy-Weinberg principle predict ?

Answer 13

predicts frequency of alleles in a population won’t change from one generation to next

Question 14

what are the certain conditions for Hardy-Weinberg principle to be true ?

Answer 14

• large population
• no immigration / natural selection / mutations
• random mating

Question 15

what can Hardy-Weinberg principle be used to calculate ?

Answer 15

estimate allele and genotype frequency within population

Question 16

Hardy-Weinberg principle allele frequency equation :

Answer 16

p + q = 1

Question 17

what do p and q stand for in Hardy-Weinberg principle

Answer 17

p : frequency of dominant allele

q : frequency of recessive allele

Question 18

Hardy-Weinberg principle genotype freq. equation :

Answer 18

p^2 + 2pq + q^2 = 1

Question 19

what do p^2 / 2pq / q^2 stand for in Hardy-Weinberg principle

Answer 19

p^2 : frequency of homozygous dominant genotype
2pq : frequency of hetrozygous genotype
q^2 : frequency of homozygous recessive genotype

Question 20

outline the process of artificial selection for dairy cattle

Answer 20

1. female w/ high milk yield selected
2. male w/ mother w/ high milk yield selected
3. mate together
4. select offspring w/ highest milk yields and breed
5. continued over generations

Question 21

outline the process of artificial selection for wheat plants

Answer 21

1. wheat plants w/ high wheat yield bred together
2. offspring w/ highest yields bred together
3. continued over generations

Question 22

what is bad about artificial selection ?

Answer 22

• reduces gene pool
• less genetic variation so may be more susceptible to disease / drought
• useful allele for medicine may be lost

Question 23

define species

Answer 23

group of similar organisms that can reproduce to give fertile offspring

Question 24

what is speciation ?

Answer 24

development of new species

Question 25

what causes speciation ?

Answer 25

reproductive isolation

Question 26

what is allopatric speciation and how does it occur ?

Answer 26

• geographical isolation (physical barrier) divides population
• different conditions favour different characteristic
• mutations occur independently
• allele frequency changes leads to phenotype frequency changing
• no longer able to interbreed and produce fertile offspring

Question 27

state the ways reproductive isolation occurs

Answer 27

• geographical isolation
• breeding seasons different times
• mechanical changes (genitals dont fit)
• behavioral (different courtship rituals)

Question 28

what is sympatric speciation ?

Answer 28

speciation as a result of mutations

Question 29

give an example of sympatric speciation

Answer 29

• mutation occurs, increasing no. of chromosomes

- polyploid may reproduce asexually, if so, a new species may form