evolution lecture 5

Question 1

What is a species?

Answer 1

difficult to make universal definition

- different concepts

Question 2

morphological species concept:

Answer 2

• based on morphological similarity
• historically, most commonly used concept
• how much difference is enough

Question 3

biological species concept

Answer 3

INTER-FERTILITY : populations that interbreed to produce fertile offspring

REPRODUCTION ISOLATION: does not normally successfully interbreed in nature with others

Question 4

Speciation

Answer 4

• reproductive barriers

Question 5

reproductive barriers

Answer 5

inhibit gene flow between populations, allowing for evolutionary divergence

Question 6

prezygotic barriers

Answer 6

barriers that happen before fertilisation

1) habitat isolation
2) temporal isolation
3) behavioural isolation
4) mechanical isolatino
5) gametic isolation (gamete incompatibility)

Question 7

postzygotic barriers

Answer 7

barriers that happen after fertilization

1) hybrid inviability
2) hybrid infertility
3) hybrid breakdown

Question 8

hybrid infertility example: mules

Answer 8

horse and donkey mate–> mule

mule is infertile

Question 9

evolution of reproductive barriers

Answer 9

-may arise by accident as a result of evolution in isolation

may evolve though netural selection (to prevent inter species mating that lowers survival rate)

Question 10

what are the two types of speciation

Answer 10

allopatric speciation

sympatric speciation

Question 11

allopatric speciation (reproductive barrier)

Answer 11

1) geographic barrier separates populations

2) evolutionary change on both sides

Question 12

if contact re-establishes between evolved allopatric speciation populations

Answer 12

1) complete reproductive barriers barriers evolved ; populations now classic biological species
2) partial reproductive barriers evolved; formation of hyrbids when species contact

Question 13

hyrbrids after re-established contact of allopatric speciation

Answer 13

FUSION: hybrids form readily; have high fitness; species merge into one again

REINFORCMENT: hybrids have low fitness; natural selection strengthens barriers

LONG LASTING hybrid zone: hybrids have variable fitness or are uncommon; species are still seperate but can have hybrids

Question 14

sympatric speciation

Answer 14

requires a barrier to gene flow within a geographic region

ex: polypoid speciation in plants

Question 15

polypoid speciation in plants

Answer 15

exception to strict “tree of life”

Question 16

speciation and tree of life

Answer 16

each branching on the tree-of-life began with speciation event