Characters provide basis for classifying Characters are traditionally phenotypic features (morphology, life cycle, etc.) But now you can also measure genetic sequences directly Homologous characters: similarities attributed to shared ancestry (e.g., mammal forelimbs) Analogous characters: similarities due to convergent evolution (e.g. wings of birds and insects)

Homology

Analogy

Analogy vs homology pitfall Is a 4-chambered heart an homologous or analogous character between mammals & birds? Homologous Analogous

“Agency” of selection At what level does natural selection occur? Darwin “organismal” But selection can act at other levels –Genes –Cells –(Organisms) –Groups (social insects) –Species?

Selection at any higher level than that of an individual is essentially "impotent“ and is "not an appreciable factor in evolution" (1966:8; cf., Williams 1992). “Many, perhaps most, evolutionary biologists believe that it [group selection] is only rarely an important force of evolution.” (Futuyma 1998, p. 352) Group vs. Individual Selection Controversy

It is sometimes said, “Group selection was vanquished in the 1960s by William Hamilton and his ‘gene’s eye view’ of selection, which is the basis of Richard Dawkins’ notion of the selfish gene.” “The fundamental unit of selection, and therefore of self-interest, is not the species, nor the group, nor even, strictly, the individual. It is the gene, the unit of heredity.” (Dawkins, 1976)

“Efficacy” of selection Does natural selection account for all of evolution? “Constraints” may channel evolution –Developmental –Structural

“Scope” of selection Can gradual microevolution account for all of evolution? What about mass extinctions? Species selection?

Your vessel (or host person) is a transient tool designed to transmit genes not necessarily live long & prosper & be happy…

An itinerant selfish gene Said ‘Bodies aplenty I’ve seen. You think you’re so clever But I’ll live for ever. You’re just a survival machine. Richard Dawkins