Chapter 24

Question 1

Species

Answer 1

Kind or appearance

Question 2

Morphological Species Concept

Answer 2

• defined by anatomical features
• practical for extant and fossil species
• difficult to apply - what is different enough
• does not explain speciation as a process

Question 3

Ecological Species Concept

Answer 3

• species can be defined by their niche
• hard to test in nature
• BUT can accommodate sexual and asexual reproduction

Question 4

Phylogenetic Species Concept

Answer 4

• the smallest group of individuals that share a common ancestor
• species are monophyletic groups
• how much difference defines a species?

Question 5

Biological Species Concept

Answer 5

• defined by reproductive isolation
• members of all populations with potential to interbreed and produce viable and fertile offspring in the wild
• sometimes difficult to apply (asexual species and fossils/extinct species)
• potential to interbreed in wild is difficult to assess
• provides insights on how species become, and remain, distinct

Question 6

Reproductive Isolation

Answer 6

• Biological factors (barriers) that impede two species from producing viable, fertile offspring
• usually more than one barrier involved
• barriers isolate species, so evolution of barriers is key to speciation
• founder population often in a different niche from parent
• founder population usually small = susceptible to genetic drift
• two populations diverge, eventually are not reproductively compatible

Question 7

Prezygotic Barriers (5)

Answer 7

Classified by timing:

1. Habitat Isolation
2. Temporal Isolation
3. Behavioural Isolation
4. Mechanical Isolation
5. Gametic Isolation

Question 8

Habitat Isolation

Answer 8

-the snakes may look alike, but one is aquatic and the other is terrestrial (water vs. dessert)

Question 9

Temporal Isolation

Answer 9

-species may mate at different times of day or during different seasons

Question 10

Behavioural Isolation

Answer 10

-species may have differences in the context of mating rituals and signals

Question 11

Mechanical Isolation

Answer 11

-ex: snails shells may wind different ways so genitals don’t line up for mating

Question 12

Gametic Isolation

Answer 12

-gametes don’t fuse therefor a zygote can’t fertilize

Question 13

Prezygotic vs. Postzygotic

Answer 13

Pre: Before fertilization
Post: After fertilization

Question 14

Postzygotic Barriers (3)

Answer 14

1. Reduced Hybrid Viability
2. Reduced Hybrid Fertility
3. Hybrid Breakdown

Question 15

Reduced Hybrid Viability

Answer 15

-Refers to lower potential to survive for organisms whose parents have incompatible genetics

Question 16

Reduced Hybrid Fertility

Answer 16

-A viable hybrid individual is sterile often due to the inability to produce normal gametes in meiosis

Question 17

Hybrid Breakdown

Answer 17

-Reproductive failure that appears after F2 generation of crosses between incompatible species

Question 18

Hybrid Zones

Answer 18

-Biological barriers not always complete-hybrids produced
-Stable hybrid populations may be established between two species - hybrid zones
-3 Outcomes Possible:
~reinforcement
~fusion
~stability
ex: two toads are isolated by habitat, but when two habitats come together, 2 species can hybridize and mix. HOWEVER MIXED TOADS WILL DEVELOP MENTAL ISSUES/BARRIERS

Question 19

Speciation

Answer 19

Two geographical Modes:

1. Allopatry
2. Sympatry

Question 20

Allopatry

Answer 20

Geographic barriers isolate population.

• geological processes
• emigration
• extinction is likely
• if they survive, they are likely to evolve relative to parent population

Question 21

Sympatry

Answer 21

Subpopulations isolated in the midst of the of the parental population.

• reduction in gene flow
• sexual selection
• habitat differentiation
• polyploidy

Question 22

Polyploidy

Answer 22

Accidents of cell division that result in reproductive isolation in a single generation

Question 23

Adaptive Radiation

Answer 23

Common ancestor spreading into many new environments over a short period of time