Macroevolution + Phylogeny

Unit 2 Chapter 5-6

Pre-Mating Reproductive Isolation

Isolating barriers that impede gene flow before sperm or pollen can be transferred to other species

• Can’t mate

Post-Mating/Pre-Zygotic Reproductive Isolation

Isolating barriers that impeded gene flow after sperm or pollen has been transferred but before fertilization has occurred

Postzygotic Isolating Barriers

Isolating barriers that act after a zygote begins to develop

Behavioral Isolation

Difference in behavior prevent members of different species from mating (Pre-Mating)

• Lack of attraction

• Flies have different mating calls

Ecological Isolation

Isolating barriers that are consequences of habitat/ecology of different species (Pre-Mating)

Mechanical Isolation

Reproductive structures don’t fit together (Pre-Mating)

• Snails are right-swirled and left-swirl snails cannot fertilize

Habitat Isolation

Species breed in different places/habitats (Ecological Pre-Mating)

• Acidic volcanic basalt on sides of volcano vs. Calcareous (basic pH) sediment in lowlands

Temporal Isolation

Species breed at different times (Ecological Pre-Mating)

• Star coral release gametes at different times

Pollinator Isolation

Flowering plants rely on different species for pollination or apply pollen to different parts of same pollinating animal (Ecological Pre-Mating)

• Bees vs. Hummingbirds specialized for certain flowers

Copulatory Behavior Isolation

Behavior of individual during copulation is insufficient to allow normal fertilization (Post-Mating/Pre-Zygotic)

• Insect don’t act or behave in certain/needed ways during sex

Gametic Isolation

Transferred sperm cannot fertilize eggs (Post-Mating/Pre-Zygotic)

• Giant Red Urchin + Purple Urchins unable to fertilize eggs

Intrinsic Isolation

Postzygotic isolation reflects a developmental problem in hybrids that is relatively independent of the environment (Post-Zygotic)

Extrinsic Isolation

Postzygotic isolation depends on environment (Post-Zygotic)

Intrinsic Hybrid Inviability

Hybrids die before or shortly after birth (Post-Zygotic)

Physiological Intrinsic Hybrid Sterility

Hybrids don’t have working reproductive system (Post-Zygotic)

• Mules

Behavioral Intrinsic Hybrid Sterility

Hybrids suffer neurological or physiological defects that prevent from finding mates (Post-Zygotic)

Ecological Extrinsic Inviability

Hybrids develop normally, but suffer lower viability because they don’t have appropriate niche  (Post-Zygotic)

• Pizzly/Grolar Bear: does not do well have intermediate phenotype

  • Different diets + Different adaptations to those diets

  • Natural selection against hybrids

Behavioral Extrinsic Sterility

Hybrids can produce normal gametes but cannot obtain mates (Post-Zygotic)

• Some flowers that are hybrid colors may never be able to attract pollinators

Root

Most recent common ancestor of all taxa included in tree

Branch

Evolutionary pathway/lineage

Node

Speciation event where one lineage splits into two or more

Clade/Monophyletic Group

A common ancestor and all of its descendants

Paraphyletic Group

Common ancestor but not all descendants

Polyphyletic Group

Does not include common ancestor

Microevolution

Natural selection, Genetic Drift, Gene Flow, Mutations within a population over few generations

Macroevolution

Speciation, extinction, adaptation radiation, long-term trends at or above the species level over many generations/geological time

Adaptive Radiation

Rapid evolution of many species from a single common ancestor