speciation

Question 1

biological species concept

Answer 1

• biological species are defined by reproductive isolation
• different biological species don’t breed in nature, breed but fail to produce offspring, produce inviable offspring, produce sterile offspring

Question 2

what are the mechanisms of isolation

Answer 2

• prezygotic isolation

- postzygotic isolation

Question 3

what is prezygotic isolation

Answer 3

• any mechanism that prevents successful mating

genotypically

Question 4

what is postzygotic isolation

Answer 4

• any mechanism that prevents the offspring from producing offspring of their own

Question 5

which is more adaptively favoured, pre or post zygotic isolation?

Answer 5

• prezygotic is much less wasted effort

- when post zygotic isolation occurs, there is natural selection for pre zygotic isolation

Question 6

what are the downsides to the biological species concept?

Answer 6

• it doesn’t apply to asexual species
• not practical to extinct species
• hard to evaluate

Question 7

the morphological species concept

Answer 7

• morphological species are different if they look different
• useful for working with fossils or diverse groups

Question 8

disadvantages to the morphological species concept

Answer 8

• subjective
• groups that look similar but can’t produce offspring
• it’s unclear how this relates to the conceptual definition evolution

Question 9

ecological species concept

Answer 9

• ecological species is a set of related organisms that occupy the same ecological niche
• commonly used for small things, like asexual

Question 10

phylogenetic species concept

Answer 10

• a phylogenetic species is monophyletic group of populations that can’t be divisible into smaller species

Question 11

what is a monophyletic group

Answer 11

• a group defined by a single common ancestor

Question 12

advantages of the phylogenetic species concept

Answer 12

• well defined

- broadly applicable

Question 13

disadvantages of the phylogenetic species concept

Answer 13

• hard to estimate phylogenies

- requires a lot of information about populations

Question 14

how are species generated?

Answer 14

• new species are generated from old species
• one species can gradually evolve into another
• species can diverge, split into two

Question 15

how do species split?

Answer 15

• genetic isolation and genetic divergence

Question 16

which comes first: isolation or divergence

Answer 16

• isolation, with too much gene flow populations can’t diverge

Question 17

what is allopatry?

Answer 17

• organisms living apart from each other

- when two populations are isolated from eachother, they might diverge

Question 18

what is dispersal?

Answer 18

• allopatry

- when some individuals in a population move to a new area and colonize it (establish a new population)

Question 19

what is vicariance?

Answer 19

• allpatry

- when a population is split by an geographical or ecological barrier

Question 20

what is sympatry

Answer 20

• organisms living in the same geographic area

Question 21

why is hard for populations in sympatry to diverge?

Answer 21

• gene flow and competition

Question 22

sympatric divergence

Answer 22

• populations are not physically isolated yet isolated by their traits (ie. preferences in food sources)

Question 23

genetic incompatiability

Answer 23

• can be caused by genetic incompatibility

- if they’re in the same place but they can’t produce fertile offspring

Question 24

polyploidy

Answer 24

• reproductive mistakes that produce individuals with with extra copies of each chromosome

Question 25

what happens when 2 isolated populations come back in contact with each other?

Answer 25

fusion or reinforcement

Question 26

what is fusion?

Answer 26

• 2 isolated populations come back together
• hybrid offspring have a high fitness
• adaptive differences may be small and overwhelmed by gene flow

Question 27

what is reinforcement?

Answer 27

• when the hybrid offspring have low fitness

- natural selection occurs for traits that reinforce the differences between the 2 species

Question 28

what are hybrid zones?

Answer 28

a geographic area where interbreeding occurs between two species, sometimes producing fertile hybrid offspring

Question 29

what is exclusion?

Answer 29

• one species may eliminate the other species, by better fitness or competition

Question 30

how can polypoidy cause speciation?

Answer 30

• these polyploids can mate and produce instant reproductive isolation and new genetic innovation