3.5 speciation

Question 1

mutation

Answer 1

a permanent and random change in the DNA base sequence

Question 2

allele frequency

Answer 2

how common an allele in a population is

Question 3

gene pool

Answer 3

total set of alleles in a population

Question 4

genetic drift

Answer 4

the random change in allele frequency due to chance events. it is necessary for evolutionary change

Question 5

founder effect

Answer 5

when a group of individuals from an existing population move to a new area and reproduce isolated from the original population. it is likely to cause fixed or lost alleles, leading the founding population to have little genetic diversity

Question 6

bottleneck effect

Answer 6

the drastic decrease of population numbers due to a sudden catastrophic event - causing an under-representation of alleles in the gene pool

Question 7

migration

Answer 7

the movement of individuals from one poplation to another, hence alleles. it usually causes genetic drift. when migrating individuals interbreed into a new population, the genetic variation is decreased, which may create new allele combinations and eliminate a unique population

emigration = leaving, immigration = entering

Question 8

gene flow

Answer 8

the movement of genes/alleles between different gene pools

Question 9

directional selection

Answer 9

favours 1 phenotype, is against the other

Question 10

disruptive selection

Answer 10

favours both extremes, goes against the average phenotype

Question 11

stabilising selection

Answer 11

favours the average phenotype, goes against both extremes

Question 12

speciation

Answer 12

a term that describes how species form. it occurs when there is little gene flow, possibly due to reproductive isolation. it can occur slowly over time or instantly

Question 13

species

Answer 13

a group of interbreeding, or potentially interbreeding, individuals which give rise to fertile offspring

Question 14

allopatric speciation

Answer 14

a type of speciation due to geographical barriers and/or isolation. it causes differences to accumulate, which are due to different selection pressures, mutations and natural selection. overtime, the populations no longer recognise each other

Question 15

sympatric speciation

Answer 15

where populations become distinct species in the same geographical location. since there is no geographical barriers, the effect of reproductive isolating mechanisms are greater. it tends to take more time to accumulate differences due to overlapping selection pressures and gene flow

Question 16

prezygotic isolating mechanisms

Answer 16

occurs before fertilisation
includes: temporal, ecological, gamete mortality, behavioural, mechanical/structural

spatial RIMS cause isolating mechanisms to develop

Question 17

postzygotic isolating mechanisms

Answer 17

occurs after fertilisation
includes: hybrid sterility, hybrid inviability, hybrid breakdown

Question 18

temporal

Answer 18

organisms reproduce and are active at different times. ex. seasonal flower bloomings and diurnal vs nocturnal animals

Question 19

ecological

Answer 19

populations live in different habitats or are in different niches

Question 20

gamete mortality

Answer 20

due to chemical differences in the egg and sperm (or pollen) , the gametes cannot fuse to become a zygote

Question 21

behavioural

Answer 21

organisms have different courtship behaviours, ex. singing and dancing. there are unique to each species and are unrecognisable to others

Question 22

structural/mechanical

Answer 22

the variation of colour, pattern, size etc… is different for each species and unattractive to another. for insects usually, mating apparatuses are also unique and specific, hence will not fit together physically

Question 23

hybrid sterility

Answer 23

healthy offspring can be produced, however, it will be sterile

Question 24

hybrid inviability

Answer 24

the zygote cannot be fully developed, usually resulting in stillbirth or miscarriages. the offspring may be born, but will die before maturity

Question 25

hybrid breakdown

Answer 25

the first generation of offspring are fertile, however, their offspring are infertile/inviable

Question 26

reason for rims

Answer 26

to preserve a species and makes the production of offspring expend the least amount of energy, which is favourable

Question 27

autoploidy

Answer 27

polyploidy occurs in the same species due to non-disjunction. usually the organism will self fertilise

Question 28

alloploidy

Answer 28

polyploidy occurs in different species, which are closely related. hybrid will not form if the species aren’t close enough. non-disjunction usually has to occur twice

Question 29

diverging evolution

Answer 29

an ancestral parent species split into 2 or more species, resulting in evolution. usually caused by rims (mostly prezygotic), selection pressures, and geographical isolation. the species produced will be quite similar due to the common ancestor

Question 30

adaptive radiation

Answer 30

rapid diverging evolution, causing large phenotypic and ecological diversity. several species will be formed by a common ancestor, which exploit different niches. it is usually in response to a new habitat, decrease in competition, or development of a new feature

Question 31

convering evolution

Answer 31

evolution of similar traits in unrelated species, usually the result of occupying similar habitats or ecological niches - which hence select for similar features. species don’t usually breed together

Question 32

parralel evolution

Answer 32

when species formed through diverging evolution from a common ancestor develop similar features (usually just one) due to changing selection pressures

Question 33

analogous

Answer 33

same function in species but did not evolve from the same ancestor. for example, bat and bird wings. they both fly but they aren’t related and the structure of the wings are different

Question 34

homologeous

Answer 34

species from the same ancestor have features that have different functional apsects. for example, humans have 5 fingers, bats have 5 segments in their wing, and whales have 5 bones in their fins