Transcript 1) Geographic Isolation

Speciation
• Defined: evolution of a new
species
• Species: group of
organisms that can
interbreed and produce
fertile offspring
• Isolation reduces gene flow
– Reproductive
– Geographical
– Behavioral
– Temporal
• Gene pools & frequencies
altered
Gene Flow
• Defined: Movement of alleles from 1 population to
another
• Increases variation
• Keeps differing populations similar
• If gene flow prevented
– No variations exchanged
– Populations isolated
– Organisms adapt to their own environment
More Sun and Rain
Less Sun and Less
Rain
Gene Flow
1) Geographic Isolation
• Mountains, rivers, canyons,
oceans may separate a
population
– Natural selection allows favorable
organisms to survive in different
environments
• Each population adapts to its
isolated environment
• Because isolated, no gene flow
Founder Effect: 14 Species of
Galapagos Finches
2) Behavioral Isolation
• Although not geographically separated,
reproduction is prevented
– 1) Different mating rituals
– 2) Use of pheromones
• No gene flow: differing populations unable to
reproduce
3) Temporal Isolation
• Although not
geographically
separated, reproduction
is prevented
– 1) Mate at different
seasons
– 2) Some noctural
• No gene flow: differing
populations unable to
reproduce
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
Quick Review
• New species are
created (speciation)
when populations
become isolated
• A changing or new
environment greatly
affects natural
selection
• I love the Far Side!