Macroevolution

Speciation - Development of new species through evolution

• occurs when populations become reproductively isolated from another and change independently

  1. Allopatric Speciation - population first separated by geographic barriers followed by reproductive isolation

  2. Sympatric Speciation - populations become reproductively isolated WITHOUT geographic Isolation

Allopatric

• Population first separated by geographic barriers followed by reproductive isolation

  • Ex. Geographic barriers (geological and climate change, Human barriers)

Sympatric

• populations become reproductively isolated without geographic isolation

  • occurs due to at least one reproductive isolating mechanism

Reproductive Isolation - Traits that prevent interbreeding and maintain reproductive isolation

• can occur before species mate (pre-zygotic) or after (post-zygotic)

Pre-zygotic Isolating Mechanisms:

• behavioral isolation - different courtship and mating rituals

• mechanical incompatibility - reproductive structures not compatible

• temporal incompatibility - different lifestyles regarding when each species is active or mating

• Habitat incompatibility - different habitats prevent interaction between species

Post-zygotic Isolating Mechanisms:

• Gametic Inviability - sperm cannot fertilize the eggs

• hybrid inviability - hybrid offspring fail to survive

• hybrid infertility - hybrid offspring are infertile or have reduced fertility

Adaptive Radiation - “Explosion of Diversity”