2.6 - variation + evolution

Question 1

what factors produce variation between individuals

Answer 1

• genetic
• environmental

Question 2

name the types of variation

Answer 2

• continuous + discontinuous
• heritable + non-heritable

Question 3

what’s discontinuous variation

Answer 3

• type of variation that can be categorised, e.g: blood group
• characteristic can only appearing discrete values
• influenced by one or two genes + environmental factors have little effect on

Question 4

what’s continuous variation

Answer 4

• type of variation that can’t be categorised, e.g: height
• produces continuous range in which a characteristic can take any value
• influenced by multiple genes + is often significantly affected by environmental factors

Question 5

compare heritable + non-heritable variation

Answer 5

heritable - genetic differences between individuals
non-heritable - acquired differences in phenotypes of individuals that can’t be inherited

Question 6

what’s evolution

Answer 6

• change in allele frequencies in gene pool of population over time
• occurs due to natural selection

Question 7

how does natural selection cause change in allele frequencies over generations

Answer 7

organisms w/ advantageous characteristics are more likely to survive + pass their favourable alleles to offspring
frequency of unfavourable alleles decreases

Question 8

what are selection pressures

Answer 8

• environmental factors that drive evolution by natural selection + limit population sizes
• can change frequency of alleles in population

Question 9

give examples of selection pressures

Answer 9

• predation
• disease
• competition (for food, habitats, mates)
• environmental conditions, e.g: temperatures

Question 10

how can allele frequencies be expressed

Answer 10

as percentage or proportion of total number of all alleles for that gene

Question 11

state the 2 types of competition

Answer 11

• interspecific
• intraspecific

Question 12

what’s interspecific competition

Answer 12

type of condition that takes place between members of different species

Question 13

what’s intraspecific competition

Answer 13

type of competition that takes place between members of same species

Question 14

define gene pool

Answer 14

all of the diff versions of genes (alleles) in individuals that make up a population

Question 15

what’s genetic drift

Answer 15

variations in allele frequencies in small populations due to chance (rather than as a result of selection pressures)

Question 16

what’s meant by the founder effect

Answer 16

when small number of individuals become isolated, forming new population w/ limited gene pool
allele frequencies not reflective of og population

Question 17

what’s the hardy-weinberg principle

Answer 17

model that allows estimation of frequency of alleles in population, as well as whether allele frequency is changing over time

Question 18

state the assumptions made by the hardy-weinberg principle

Answer 18

• no mutations occur to create new alleles
• no migration in/out of populations
• no selection, alleles all equally passed on to next generation
• random mating
• large population

Question 19

explain the hardy-weinberg equation for calculating allele frequency

Answer 19

frequencies of each allele for characteristic must add up to 1, giving the equation: p + q = 1

p = frequency of dominant allele
q = frequency of recessive allele

Question 20

explain the hardy-weinberg equation for calculating genotype frequency

Answer 20

frequencies of each genotype for characteristic must ad up to 1, giving equation: p^2 + 2pq + q^2 = 1

p^2 = frequency of homozygous dominant
2pq = frequency of heterozygous
q^2 = frequency of homozygous recessive

Question 21

define speciation

Answer 21

formation of new species due to evolution of 2 reproductively separated populations

Question 22

why may speciation occur

Answer 22

• genetic drift in isolated population
• founder effect
• natural selection

Question 23

what are the 2 types of speciation

Answer 23

• allopatric speciation
• sympatric speciation

Question 24

what is allopatric speciation

Answer 24

occurs when 2 populations become geographically isolated

Question 25

what is sympatric speciation

Answer 25

occurs when 2 populations within same area become reproductively isolated

Question 26

outline geographical isolation

Answer 26

physical barrer (e.g: river or mountain) separates 2 populations of the same species

Question 27

name the potential isolation mechanisms in sympatric speciation

Answer 27

- morphological isolation - seasonal isolation - behavioural isolation - gametic isolation - hybrid sterility - hybrid inviability

Question 28

what’s morphological isolation

Answer 28

reproductive isolation of 2 populations due to incompatibility of reproductive systems

Question 29

what’s behavioural isolation

Answer 29

reproductive isolation of 2 populations due to differences in behaviour (e.g: diff mating rituals)

Question 30

describe seasonal isolation

Answer 30

reproductive isolation of 2 populations due to differences in their breeding seasons

Question 31

describe hybrid inviability

Answer 31

- pos-zygote barrier - successful fertilisation but embryo can’t develop into living organsim

Question 32

what’s hybrid sterility

Answer 32

formation of sterile offspring from reproduction of individuals of different species

Question 33

why may reproduction of individuals of different species produce sterile offspring

Answer 33

chromosome sets from each parent differ so can’t pair up during meiosis

Question 34

give examples of a sterile hybrid + a fertile hybrid

Answer 34

sterile - mule fertile - wheat

Question 35

what is gametic isolation

Answer 35

- prezygotic barrier - successful fertilisation doesn’t occur

Question 36

what is gametic isolation

Answer 36

- prezygotic barrier - successful fertilisation doesn’t occur