Macroevolution

Macroevolution

• Speciation

• making of new species

Coevolution

Two connected species evolve together

Parapatric Speciation

• Species separated due to wide habitat

• Breeding restricted to a vicinity

Allopatric Speciation

• Geographical Isolation

• Reproductively isolated

Paripatric Speciation

• Same as allopatric but one group is XL and other is XS

• Similar to founder’s effect

• lower allele frequency

• Sample separated from population due to physical barriers

Sympatric Speciation

• same area

• Postzygotic & Prezygotic

Postzygotic Barriers

• Infertility

• Undeveloped embryo

• Weak, ungrowable embryo

Prezygotic Barriers

• Temporal: time difference (day, night)

• Behavioral: prefered trait of mates (songs)

• Habitat: location (water, mud)

• Mechanical: Change in body parts/ different organs

Microevolution

Changes within one species

Ways to change a gene pool (Microevolution)

• Sexual selection

• Natural selection

• Gene flow

• Genetic drift

• Mutations

Genetic Drift

• Random events

• Changes gene pool

• Founder’s and bottleneck effect

Gene Flow

• Non-random

• May introduce new variants

• Gene transfer from one population to another

• If stopped, population separates and changes independently

Fitness

• Most represented genes

• Most genes passed on to next generation

• Those who contribute the most to gene pool

Directional Selection

• Averages move left or right

• One extreme is favoured over average

Disruptive Selection

• Average is eliminated

• Extremes are favoured

Stabilizing Selection

• Eliminates extremes

• Common becomes more common

Bottleneck Effect

• Population becomes tiny due to disasters

• Survivors have less genetic variety

• Future generations are genetically similar

Founder’s Effect

• A sample leaves population and starts new one

• New population has only genes of sample

• Genetic variety is lower and some traits may become common

Divergent Evolution

AKA Adaptive Radiation

Potential problem

• Lack of intermediate fossils

• Solution: Punctuated Equilibrium

Punctuated Equilibrium

• Stasis

• Isolation

• Rapid change

• Expansion & stasis

• Preservation