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An Introduction to Life,Evolution, and Extinctions

Brad Hubeny

Taxonomy as a Tool for Classification

A FamiliarExample

Phylogeny andEvolution

Phylogenyand

Evolution

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Phylogeny and Evolution Evolution• Adaptations

– Specialized features ofanimals and plants thatperform one or moreuseful functions

– Allow that organismto excel in itsenvironment

Charles Darwin

Natural Selection

Galapagos Tortoises

• Additional observations– Anatomical relationships

• Embryos of many vertebrates quite similar• Homology

– Presence in two different groups of animals orplants of organs that have the same ancestralorigin but serve different functions

• Vestigial organs– Organs that serve no apparent purpose but

resemble organs that perform functions in othercreatures

Genes, DNA, and Chromosomes

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Genes, Evolution, and Speciation• Sexual recombination

– Each parent contributes one-half of its chromosomes tooffspring

– Yields new combinations• Mutations increase variability

• Gene pool– Sum total of genetic components of a population or

group of interbreeding individuals• Reproductive barriers limit the pool

• Speciation– Origin of a new species from two or more individuals

of a preexisting species

Evolutionary Radiations

Hexacorals

Extinction Rates of Ammonoids Mass Extinctions