Chapter 11. Evolution and the Diversity of Life

Evolution is change in the inherited characteristics of populations over generations. Darwin and Wallace proposed natural selection as a major mechanism [10][15].

Natural selection requires:

Variation among individuals.

Inheritance of traits.

More offspring produced than can survive.

Differential survival and reproduction linked to traits.

Evidence for evolution: the fossil record, comparative anatomy (homologous structures), embryology, biogeography, direct observation (such as antibiotic resistance in bacteria) and DNA comparisons [10].

Other mechanisms: mutation, gene flow, genetic drift and sexual selection. A species is commonly defined as a group of organisms that can interbreed and produce fertile offspring, though this definition has limits.

Classification. Living things are grouped hierarchically: domain, kingdom, phylum, class, order, family, genus, species. The three domains are Bacteria, Archaea and Eukarya. Scientific names use two parts, genus and species (Homo sapiens).

Earth’s history. Earth formed about 4.5 billion years ago; the earliest evidence of life is more than 3.5 billion years old [11][12].

Review: Why does antibiotic resistance illustrate natural selection? (Answer: resistant bacteria survive treatment and reproduce, so resistance becomes more common in the population.)