18.6 — speciation

Question 1

what is a species?

Answer 1

a species is a group of individuals that are capable of breeding with one another to produce fertile offspring

Question 2

individuals within a species share the same _____ but typically have different _______

Answer 2

genes/alleles

Question 3

what is speciation?

Answer 3

the process by which new species are formed

Question 4

why does speciation typically occur?

Answer 4

1. reproductive isolation of populations, which is the inability of two groups of organisms to breed with one another
2. genetic divergence driven by natural selection and genetic drift

Question 5

what does genetic drift refer to?

Answer 5

the random changes in allele frequencies within a population’s gene pool, due to chance events, not as a result of natural selection

Question 6

where is genetic drift most influential?

Answer 6

in small isolated populations, where it can accelerate speciation

Question 7

what is adaptive radiation?

Answer 7

a phenomenon where organisms diversify rapidly from an ancestral species into a wide array of new forms, each adapted to a specific ecological niche

Question 8

when is adaptive radiation is most likely to occur?

Answer 8

when a change in the environment makes new resources available

Question 9

what is reproductive isolation?

Answer 9

when populations cannot interbreed successfully to produce viable, fertile offspring

Question 10

what is genetic isolation?

Answer 10

when a lack of gene flow between populations due to reproductive barriers mean they cannot interbreed successfully

Question 11

what does a lack of interbreeding do?

Answer 11

prevents the exchange of genes between the populations — facilitating speciation

Question 12

what two barriers can reproductive isolation result from?

Answer 12

prezygotic barriers or postzygotic barriers

Question 13

what do prezygotic and postzygotic barriers do?

Answer 13

ensure the genetic uniqueness of diverging populations, even when they come into contact again

Question 14

what do prezygotic barriers prevent?

Answer 14

fertilisations and teh formation of a zygote — act before the fertilisation of an egg cell

Question 15

what are examples of prezygotic barriers?

Answer 15

habitat isolation or variations in mating rituals

Question 16

what are postzygotic reproductive barrier usually a result of?

Answer 16

hybridisation between different species

Question 17

what does hybridisation produce and what does it do?

Answer 17

infertile or non-viable offspring — reducing their reproductive potential

Question 18

what are the main types of speciation?

Answer 18

allopatric and sympatric

Question 19

what are the stages of allopatric speciation?

Answer 19

1. members of a population are geographically separated from the rest by a physical barrier (e.g mountain, rivers of seas)
2. geographical separation exposes distinct parts of the population to different enviromental pressures
3. the prezygotic reproductive barriers lead to reproductive isolation
4. reproductive isolation prevents gene flow, and the physical separation leads to genetic divergence

5, this causes the populations to evolve separately and form separate species

Question 20

what are the stages of sympatric speciation?

Answer 20

1. takes place within the same geographical location
2. ecological or behavioural separation mechanisms (different habitat preference, mate selection, chromosomal change) lead to the groups becoming reproductively isolated
3. reproductive isolation prevents gene flow and leads to genetic divergence
4. this causes the populations to evolve separately and form separate species

Question 21

what speciation is less frequent?

Answer 21

sympatric speciation

Question 22

where is sympatric speciation more common?

Answer 22

in plants, rather than animals