lecture 19

Question 1

two ways to disrupt gene flow

Answer 1

reproductive isolation, geographic isolation

Question 2

three steps for speciation

Answer 2

1. isolation of populations
2. divergence of populations
3. evolution of reproductive barriers

Question 3

geography speciation

Answer 3

allopatric (peripatric and peripheral isolates), parapatric, sympatric

Question 4

allopatric

Answer 4

non overlapping w a gap

Question 5

peripatric

Answer 5

allopatric, but two similar sized populations

Question 6

peripheral isolates

Answer 6

allopatric but populations vary in size (easiest for speciation to occur because small pop. size reaches fixation faster)

Question 7

divergence of populations

Answer 7

what makes two populations different species. may or may not affect the ability to interbreed

Question 8

types of divergence

Answer 8

1. local adaptation (natural selection)
2. sexual selection
3. genetic drift

Question 9

evolution of reproductive barriers

Answer 9

1. prezygotic
2. postzygotic
3. instantaneous

Question 10

prezygotic reproductive barriers (5)

Answer 10

• temporal isolation
• habitat isolation
• behavioral or sexual isolation
• mechanical isolation
  -gametic incompatibility

Question 11

postzygotic reproductive barriers (4)

Answer 11

• zygote mortality
• hybrid inviability
• hybrid sterility
• hybrid breakdown

Question 12

temporal isolation

Answer 12

different mating times

Question 13

habitat isolation

Answer 13

different ecological niches

Question 14

behavioral or sexual isolation

Answer 14

mating preferences differ (sexual selection)

Question 15

mechanical isolation

Answer 15

mating occurs but gametes are not transferred due to incompatible reproductive structures

Question 16

gametic incompatibility

Answer 16

incompatible sperm and eggs that meet but do not fertilize

Question 17

zygote mortality

Answer 17

zygote dies

Question 18

hybrid inviability

Answer 18

hybrid has lower fitness

Question 19

hybrid sterilty

Answer 19

hybrid is sterile

Question 20

hybrid breakdown

Answer 20

reduced viability or fertility but is seen 1-2 generations later

Question 21

reinforcement

Answer 21

process in which selection acts to reduce interbreeding through assortative mating (nonrandom mating)
- accelerates speciation

Question 22

instantaneous isolation mechanisms

Answer 22

1. chromosomal rearrangements
2. polyploidy
3. hybridization

Question 23

chromosomal rearrangements

Answer 23

changes in chromosome structure causes incorrect pairing and thus incompatibility

Question 24

polyploidy

Answer 24

when an organism has more than 2n chromosome sets and cannot reproduce with diploid relatives

Question 25

hybridization

Answer 25

when two distinct species interbreed and form a hybrid offspring that is its own distinct species more common in plants because: 1. plants propogate so may not need to be fert again 2. can tolerate polyploidy