genetics (evolution)

Question 1

what is variation?

Answer 1

the differences that exist between individuals

Question 2

what does variation within a species mean?

Answer 2

the individuals can show a range of phenotypes

Question 3

what causes genetic variation within a species?

Answer 3

mutations
meiosis
random fertilisation
the environment

Question 4

what type of variation results in evolution?

Answer 4

genetic

Question 5

what is evolution?

Answer 5

when the frequency of an allele in a population changes over time

Question 6

what are selection pressure?

Answer 6

environmental factors that limit the population of a species

Question 7

what is the gene pool?

Answer 7

total number of alleles of all the genes of all individuals of a population during a given time

Question 8

how does natural selection occur?

Answer 8

1) individuals of the same species vary due to differences in alleles
2) predation, disease and competition create a pressure for survival
3) as individuals vary, some are better adapted to deal with selection pressures than others
4) individual with a phenotype that increases their chance of survival is more likely to survive/reproduce/pass on genes
5) greater proportion of a population inherit beneficial alleles
6) more likely to survive/reproduce/pass on genes
7) frequency of beneficial allele increases across generations

Question 9

what is stabilising selection?

Answer 9

where individuals with alleles for characteristics towards the middle of the range are most likely to survive and reproduce

occurs when the environment isn’t changing and reduces the range of phenotypes

Question 10

what is directional selection?

Answer 10

individuals with alleles for a single extreme phenotype are more likely to survive and reproduce

could be in response to an environmental change

Question 11

what is disruptive selection?

Answer 11

where individuals with alleles for extreme phenotypes at either end of the range are most likely to survive and reproduce

occurs when the environment favours more than one phenotype

Question 12

what is speciation?

Answer 12

development of a new species from an existing species

Question 13

when does speciation occur?

Answer 13

members of the same species become reproductively isolated

Question 14

what is allopatric speciation?

Answer 14

speciation that occurs due to a physical barrier- geographical speciation

Question 15

what is sympatric speciation?

Answer 15

when a population becomes reproductively isolated without any physical separation

Question 16

why does geographical isolation lead to allopatric speciation?

Answer 16

experience different conditions on different sides of the geographical barrier

Question 17

what are the stages of allopatric speciation?

Answer 17

physical barriers stop interbreeding between populations

populations adapt to the new environments

allele frequency and phenotype frequencies change which leads to the development of a new species

Question 18

why does sympatric speciation occur?

Answer 18

populations become reproductively isolated due to differences in their behaviour

Question 19

why could sympatric speciation result?

Answer 19

random mutations prevent breeding

Question 20

what changes could occur as a result of mutations which affects speciation?

Answer 20

seasonal eg) sexually active at different times of the year
mechanical eg) changes in genitalia prevent successful mating
behavioural eg) courtship rituals that aren’t attractive

Question 21

how can genetic drift lead to evolution?

Answer 21

individuals within a population show variation in their genotypes
the allele for one genotype is passed onto the offspring more often than others by chance
number of individuals with the allele increases
changes in allele frequency in two isolated populations could eventually lead to reproductive isolation/speciation

Question 22

where does evolution by genetic drift have a greater effect?

Answer 22

in smaller populations where chance has a greater influence