10.3 gene pools and speciation

Question 1

what is a species

Answer 1

a group of organisms that can interbreed to produce fertile offspring

Question 2

what is a population

Answer 2

individuals of the same species living in the same place and time

Question 3

what is a gene pool

Answer 3

the set of all variations of all genes present in an interbreeding population

Question 4

what is allele frequency expressed as in a gene pool?

Answer 4

percentage or proportion

Question 5

what are the forces of change in a gene pool

Answer 5

random genetic drift
emigration / immigration
selective predation
mutation
founder effect

Question 6

what is random genetic drift

Answer 6

sudden hostile physical conditions sharply reduce natural pop to v few survivors
eg: cold, flooding, drought

Question 7

what is mutation + how it is a force of change in gene pool

Answer 7

random, rare, spontaneous changes in the genes occur in gonads, leading to possibility of new characteristics in the offspring

Question 8

what is the Founder effect

Answer 8

a barrier may arise within a population, instantly isolating a small sample of the original pop – may be carrying unrepresentative selection of gene pool, but will be the basis of the new population – another form of genetic drift

Question 9

what is the prerequisite for evolution

Answer 9

genetic variation

Question 10

what happens when populations are isolated from each other?

Answer 10

genetic drift
different selective pressure

cause pops to evolve differently
when differences accumulate –> speciate

Question 11

what are the different types of selections (3)

Answer 11

stabilising
directional
disruptive

Question 12

what happens in stabilising selection?

Answer 12

occurs when the existing variations that are beneficial are already common
stabilising selection acts against extremes of a trait
usually remain as one species

Question 13

what happens in directional selection

Answer 13

occurs when one extreme of a trait offers a survival or reproductive advantage
increases allele freq at one phenotypic extreme, reducing them at other
usually remains as one species

Question 14

what happens in disruptive selection

Answer 14

most frequent phenotype becomes a disadvantage, individuals at both extremes have better rates of survival and reproduction
population may break into 2 species

Question 15

what is the Hardy-Weinberg formula

Answer 15

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

p^2: frequency of homozygous dominant individuals
2pq: frequency of heterozygous individuals
q^2: frequency of homozygous recessive individuals

Question 16

what is speciation

Answer 16

formation of one or more new species from an ancestral species

Question 17

what does speciation require

Answer 17

genetic variation, time and selective pressure

Question 18

what is reproductive isolation

Answer 18

failure of individuals from two populations to mate and produce fertile offspring

Question 19

what does reproductive isolation result in

Answer 19

elimination of gene flow between the populations

Question 20

what are the 3 main isolation barriers

Answer 20

geographic
behavioural
temporal

Question 21

what happens in geographic isolation

Answer 21

separation of populations by a physical barrier reducing/ preventing gene flow

allopatric speciation: new species emerging during geographic separation of a population from other populations

Question 22

what happens in behavioural isolation

Answer 22

any genetically-influenced difference in behaviour that acts to reduce / eliminate gene flow between portions of a population

sympathetic speciation: when a portion of a population develops into a new species while living in the same geographic area as the ancestral population

Question 23

what happens in temporal isolation

Answer 23

any shift in timing of a behaviour that acts to reduce or eliminate gene flow between portions of a population

occurs when portions of a population are reproductively actively at different times
eg: portions of the population may mate or flower at different times of day / seasons

Question 24

rates of speciation (3)

Answer 24

GRADUALISM
ABRUPTLY
PUNCTUATED EQUILIBRIUM

Question 25

GRADUALISM

Answer 25

occurs when major changes are the cumulative product of slow but continuous minor changes

mutation or immigration occasionally introduces new alleles to the gene pool, which are then acted on by natural selection, becoming more common or disappearing

Question 26

PUNCTUATED POLYPLOIDY

Answer 26

implies long periods without appreciable change and short periods of rapid evolution
species generally stable during long periods while stabilising selection works to maintain the existing phenotype of the species

however, periods of stability are punctuated by rapid busts of phenotypic change
often result of major upheavals such as long-term climate shifts / arrival (through immigration of evolution) of a new species with strong ecological impact
stabilising selection would shift to directional or disruptive selection

Question 27

what is polyploidy

Answer 27

refers to the presence of more than two complete sets of chromosomes in a cell

can be caused by the total non-disjunction of chromosomes during mitosis or, most commonly, meiosis 1