population genetics

Question 1

what is evolution

Answer 1

process where inherited characteristics of a population change over generations

Question 2

influeneces of evolution via altering allele frequencies

Answer 2

.mutation introduces new alleles and genetic variation

.gene flow is the transfer alleles between populations

.genetic drift causes random changes in allele frequencies

.natural selection increases the frequency of alleles that improve surival and reproduction rate

.sexual selection increases the frequency of alleles that improve reproduction rate

Question 3

genetic drift

Answer 3

random changes in allele frequencies within a population due to chance events

.influential in small isolated population

Question 4

population genetics

Answer 4

.examines the variation in allele frequencies over time

Question 5

population size in relation to natural selection

Answer 5

.size of population effects its genetic variation which determines the potential of natural selection

.large = large gene pool/high diversity = higher potential for natural selection

.small = small gene pool/low diversity = lower potential for natural selection

Question 6

two types of factors that limit population

Answer 6

density-dependent factors - depends on the size of the population
e.g. competition, predation and disease

density-independent factors - impact population regardless of the size
e.g. natural disasters and climate change

Question 7

bottleneck effect

Answer 7

.occurs when a population size reduces rapidly
.lasts for atleast one generation
.leads to reduced gene pools so less genetic diversity
.decreases diversity = reduced fertility
.may cause mutations to become more prevalent

Question 8

founder effect

Answer 8

.small groups splits from a larger population creating a new smaller population

.leads to reduced gene pool = reduced genetic diversity
.rare alleles from original population become more common (extreme genetic drift)

Question 9

how variation drives evolution

Answer 9

.generates range of phenotypes within a population = alleles with advantageous traits

.individuals with the advantageous alleles are more likely to survive and reproduce
.so transmitting their advantageous alleles to their offspring causing nautral selection

Question 10

directional selection

Answer 10

.selects for one extreme phenotype over others
e.g. antibiotic resistance in bacteria

.shifts curve to direction of favoured extreme

Question 11

stabilising selection

Answer 11

.selects for the average phenotype and against the extreme phenotypes
e.g. human birth weight

.narrows the curve

Question 12

disruptive selection

Answer 12

.selects for extreme phenotypes and against average phenotypes
e.g. bird beaks becoming bigger/smaller when there was two different food sources

.curve shifts into multiple peaks where the average phenotypes was weak

Question 13

reproductive isolation

Answer 13

when populations cannot interbreed to produce fertile offspring

Question 14

genetic isolation

Answer 14

lack of gene flow between populations due to reproductive barriers

Question 15

prezygotic reproductive barriers

Answer 15

.prevent fertilisation and the formation of a zygote
.act before the fertilisation of an egg cell
e.g. habitat isolation, variation in mating rituals

Question 16

postzygotic reproductive barriers

Answer 16

.result in hybridisation between different species
.produce infertile or non-viable offspring

Question 17

allopatric speciation

Answer 17

.members are separated from the rest of the population via physical barriers
.the two new populations are exposed to different enviromental pressure
.the prezygotic reproductive barriers lead to reproductive isolation
.this prevents gene flow and eventually lead to genetic divergence
.this causes the populations to evolve separately and form different species

Question 18

sympatric speciation

Answer 18

.ecological or behavioural separation mechanisms like habitat preference, mate selection leads to groups becoming reproductively isolated
.reproductive isolation prevents gene flow and leads to genetic divergence
.causing populations to evolve separately and form separative species

Question 19

adaptive radiation

Answer 19

when organisms diversify rapidly into a wide array of new forms

Question 20

aritificial selection

Answer 20

when humans breed organisms selectively for specific traits

Question 21

what is the Hardy-Weinberg principle

Answer 21

.calculates the frequencies of alleles for a particular gene within a population

total possible allele combinations
p^2 + 2pq + q^2 = 1

sum of alleles for a gene in the pop

p + q = 1

p = dominant
q = recessive

Question 22

assumptions of the hardy-Weinberg principle

Answer 22

.no mutations
.no migrations
.mating is random
.pop size is large
.no natural selection pressure