Unit 3 Flashcards
Evolution (18 cards)
Reproductive Isolating Mechanisms
Factors that prevent populations from interbreeding
Prezygotic mechanisms
Prevent fertilization and zygote formation
Postzygotic mechanisms
Prevent fertilized egg from growing into viable reproducing adult
5 prezygotic mechanisms
- Behavioural Isolation
- Temporal Isolation
- Ecological Isolation
- Mechanical Isolation
- Gametic Isolation
Behavioural Isolation
Diff species use diff courtship/mating calls
Temporal Isolation
Diff species breed at diff times of the year
Ecological Isolation
Very similar species may occupy diff habitats within region
Mechanical Isolation
Differences in morphological features may make 2 species incompatible
Gametic Isolation
Male gametes may not be able to recognize & fertilize egg of diff species
Example of behavioural isolation
Birds of paradise have different bird calls & mating rituals
Example of temporal isolation
American Toad – mates in early summer
Fowler’s Toad – mates in late summer
Example of ecological isolation
One cricket species lives in sandy soils, another lives in loamy/grassy soils
Example of mechanical isolation
Male damselfly species have diff claspers to attach to females when mating
Example of gametic isolation
Red & purple sea urchins live in same habitat but gametes are chemically incompatible
3 postzygotic mechanisms
- Zygotic mortality
- Hybrid inviability
- Hybrid infertility
Zygotic mortality (sheep x goat)
Genetic differences result in zygote unable to develop properly
Hybrid inviability (leopard x tiger – leoger)
Hybrid individual develops but either dies before birth / cannot survive to maturity
Hybrid infertility (horse x donkey, lion x tiger – liger, tiger x lion – tigon)
Hybrid individual healthy and viable, but cannot reproduce
