Lecture Notes: Understanding Evolution

Introduction to Evolution

Biological Evolution: Changes in inherited traits of a population over generations.
Populations, not individuals, evolve.
Populations consist of organisms of the same species but with genetic variety.

Gene Flow: Movement of genes between populations, often through migration.
Mutations: Changes in genetic material, can be harmful, beneficial, or neutral.
Genetic Drift: Random events causing changes in a population’s genetic makeup (e.g., a lawn mower affecting grasshoppers).
Natural Selection: Favorable traits become more common as they enhance survival and reproduction.
- Example: Green grasshoppers are better camouflaged and pass on their genes.

Molecular Homologies: Similarities at a molecular level (e.g., DNA, proteins).
- Animals in Eukarya share common ancestry.
- Example: Turkey and emu are more related than turkey and termite.
Anatomical Homologies:
- Homologous Structures: Similar structures from common ancestors (e.g., human arms, dog forelimbs).
- Analogous Structures: Similar functions but different evolutionary origins (e.g., bird wings vs. insect wings).
- Vestigial Structures: Inherited but lost most function (e.g., chicken wing claws).
Developmental Homology: Similar embryos can indicate shared ancestry (e.g., Chordata phylum traits).

Study of species distribution geographically supports evolution.
Island populations evolve independently but are related to nearest land masses.
Examples: Marsupials in Australia and South America share ancestry due to continental drift.

Evolution is continuous, not a finished process.
Observable in fast-generating species (e.g., antibiotic resistance in bacteria).

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