Download 11.5 Speciation Through Isolation Populations can

11.5 Speciation Through Isolation
KEY CONCEPT
New species can arise when populations are isolated.
11.5 Speciation Through Isolation
The isolation of populations can lead to speciation.
• Populations become isolated when there is no gene flow.
– Isolated populations adapt to their own environments.
– Genetic differences can add up over generations.
11.5 Speciation Through Isolation
• Reproductive isolation can occur between isolated
populations.
– members of different
populations cannot
mate successfully
– final step to
becoming separate
species
• Speciation is the rise of two or more species from one
existing species.
11.5 Speciation Through Isolation
Populations can become isolated in several ways.
1. Behavioral barriers can cause isolation.
– called behavioral isolation
– includes differences in courtship or mating behaviors
• Although not geographically separated, reproduction is
prevented
– 1) Different mating rituals
– 2) Use of pheromones
• No gene flow: differing populations unable to reproduce
11.5 Speciation Through Isolation
2. Geographic barriers can cause isolation.
– called geographic isolation
– physical barriers divide population
11.5 Speciation Through Isolation
11.5
SpeciationEffect:
Through Isolation
Founder
14 Species
Galapagos Finches
of
13.1 Ecologists Study Relationships
3. Temporal barriers can cause isolation.
– called temporal isolation
– timing of reproductive periods prevents mating
Although not geographically
separated, reproduction is prevented
– 1) Mate at different seasons
– 2) Some noctural
No gene flow: differing populations
unable to reproduce
11.5
Speciation
Through
Isolation
End
Result:
Reproductive
Isolation
• Created as a result of
behavioral, geographical,
& temporal isolation
• No mating between
populations (no gene
flow)
• Two groups unable to
reproduce
– Sex organs don’t
match, rituals don’t
attract, physically
separated
• Species: group of
organisms that can
interbreed and produce
fertile offspring