Speciation

Question 1

Biological species concept

Answer 1

defined by reproductive isolation

Question 2

Different biological species either:

Answer 2

– Don’t breed in nature
– Breed but fail to produce offspring
– Produce inviable offspring
– Produce sterile offspring

Question 3

inviable offspring

Answer 3

offspring do not develop to adulthood

Question 4

sterile offspring

Answer 4

offspring that cannot reproduce

Question 5

Prezygotic isolation

Answer 5

any mechanism that prevents successful mating

Question 6

Postzygotic isolation

Answer 6

any mechanism that prevents offspring from producing offspring of their own

Question 7

Morphological species concept

Answer 7

defined to be different if they look different

Question 8

Disadvantages of the Morphological species concept

Answer 8

• Subjective
• groups can look very similar but can’t produce viable offspring
• Not clear how definition relates to our conceptual definition of evolutionary units

Question 9

Ecological species concept

3 points

Answer 9

set of related organisms occupying the same ecological niche

• Exploit similar resources
• Tolerate similar environments
• Face similar natural enemies

Question 10

Phylogenetic species concept

Answer 10

monophyletic group of populations

Question 11

Advantages of Phylogenetic species concept

Answer 11

• Well defined

- Broadly applicable

Question 12

Disadvantages of Phylogenetic species concept

Answer 12

• Hard to estimate phylogenies

- Requires a lot of information about populations

Question 13

diverge

Answer 13

one species splits into two species

Question 14

How do species split?

Answer 14

• Genetic isolation
• Genetic divergence
• usually isolation come first (w too much gene flow pop can’t diverge)

Question 15

Allopatry

Answer 15

organisms living apart from each other

Question 16

Dispersal

Answer 16

Isolated populations of the same species can develop if some individuals disperse
(move) to a new area and colonize it (establish a new population).

Question 17

Vicariance

Answer 17

Isolated populations of the same species can develop when a population is split by a geographical or ecological barrier

Question 18

Sympatry

Answer 18

organisms living in the same geographic area

Question 19

Genetic incompatibility

Answer 19

• Divergence can occur when mutation causes genetic incompatibility (if 2 pop in same area but cannot produce fertile offspring)
• Genetic incompatibility is less likely to produce divergence than physical separation

Question 20

Polyploidy

Answer 20

Reproductive mistakes can occur that produce individuals with extra copies of each chromosome

Question 21

What happens when isolated populations come back into contact?

Answer 21

Usually this happens when a geographic barrier disappears

1. Fusion
2. Reinforcement

Question 22

Fusion

Answer 22

When two isolated populations come into contact, they may fuse back together

Question 23

Reinforcement

Answer 23

• hybrid offspring may have low fitness
• In these cases, we expect natural selection for traits that reinforce the distinction between the two species
• They avoid mating, using coloration, timing, courtship rituals

Question 24

Hybrid zones

Answer 24

When hybrid offspring are functional, and well-adapted to the overlap zone, there may be a zone where hybrids occur

Question 25

Exclusion

Answer 25

One species might eliminate the other species, either by competition, or by better success in mating

Question 26

Disadvantages to Biological Species concept

Answer 26

• does not apply to asexual species
• not practical for extinct species
• may be difficult to evaluate