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Evolution by Natural Selection - Coggle Diagram
Evolution by Natural Selection
Introduction to new alleles by mutation
Barriers to Gene Flow
Allopatric: different area
Sympatric: two species live close together but can't interbreed due to a mutation or subtle changes in behavior
Behavioral: Behavior patterns (songs, rituals) are unique to a certain species
Temporal: Species breed during different times of day/seasons and therefore cannot interbreed
Example: Eastern Spotted Skunk and Western Spotted skunk -- they breed in different seasons
Speciation (through reproductive isolation)
Polyploidy
: Organisms containing more than two homologous chromosome sets
Daughter species produced through polyploidy cannot breed with individuals in the parent species because the chromosomes can't pair up properly. Example: Plants
Theories on time for evolutionary change
Gradualism
: Evolution occurs by the gradual accumulation of small changes.
Punctuated equilibrium
: Evolution occurs with punctuated short periods of rapid evolution
Selection Pressures
Disruptive selection
Example: Rabbits
In an environment with black and white rocks, white and black rabbits live because they are camouflaged. Grey rabbits die because they are visible and are targeted by predators.
Stabilizing selection
Example: Human babies
Lightweight and heavyweight babies have higher mortality rate than average weight babies
Directional selection
Example: Giraffes
Short neck giraffes could not reach leaves on tree and died; Long neck giraffes prospered because they could reach the leaves. Long neck individuals survived and left offsprings.
