Evolution and Classification Notes

Vestigial Structures:

• Features with no current function, remnants from ancestors.
• Examples:
• Pelvic bones in snakes
• Appendix in humans
• Whale pelvis
• Eyes in blind cave salamanders/fish

Embryonic Development:

• Similarities in embryos of different species reveal evolutionary connections.
• Chicken, pig, and fish embryos are similar at certain development stages.

DNA and Molecular Clocks:

• DNA comparisons help determine evolutionary relationships.
• Scientists use silent mutations as a timeline to measure evolutionary time.
• Common ancestry implies that species with more DNA differences have diverged longer ago.

Cladograms:

• Visual representations of evolutionary relationships; show common ancestors and branching lineages.
• Example: Cladogram of the cat family showing how traits emerged over time.

Taxonomy and Clades:

• Modern clades link organisms by common ancestry, defining groups more accurately than traditional taxonomies.
• Clade definitions:
• Clade is a group containing a common ancestor and all its descendants.

Finches and Natural Selection:

• Study of Galápagos finches shows relationship between beak size/shape and survival.
• Differences in beak traits are influenced by environmental pressures (food sources).

Speciation Mechanisms:

• How new species arise involves:
• Reproductive Isolation: No interbreeding occurs.
• Behavioral Isolation: Differences in mating rituals.
• Geographic Isolation: Physical barriers separate populations.
• Temporal Isolation: Species reproduce at different times.

Natural Selection:

• Process by which species evolve due to adaptive traits that enhance survival and reproduction.
• Observational evidence shows that trait variation contributes to evolutionary change.