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Flashcards in Chapter 24 Deck (23):
1

Species

Kind or appearance

2

Morphological Species Concept

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

3

Ecological Species Concept

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

4

Phylogenetic Species Concept

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

5

Biological Species Concept

-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

6

Reproductive Isolation

-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

7

Prezygotic Barriers (5)

Classified by timing:
1. Habitat Isolation
2. Temporal Isolation
3. Behavioural Isolation
4. Mechanical Isolation
5. Gametic Isolation

8

Habitat Isolation

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

9

Temporal Isolation

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

10

Behavioural Isolation

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

11

Mechanical Isolation

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

12

Gametic Isolation

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

13

Prezygotic vs. Postzygotic

Pre: Before fertilization
Post: After fertilization

14

Postzygotic Barriers (3)

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

15

Reduced Hybrid Viability

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

16

Reduced Hybrid Fertility

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

17

Hybrid Breakdown

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

18

Hybrid Zones

-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*

19

Speciation

Two geographical Modes:
1. Allopatry
2. Sympatry

20

Allopatry

Geographic barriers isolate population.
-geological processes
-emigration
-extinction is likely
-if they survive, they are likely to evolve relative to parent population

21

Sympatry

Subpopulations isolated in the midst of the of the parental population.
-reduction in gene flow
-sexual selection
-habitat differentiation
-polyploidy

22

Polyploidy

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

23

Adaptive Radiation

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