Overview of Evolutionary Biology Darwin’s idea of evolution caused a “paradigm shift” – a new way of looking at and understanding living things – a natural explanation for the commonalities and diversity of living things Presented two major ideas • common descent • natural selection Common descent explains common features of organisms – anatomy, biochemistry, behavior, … Natural selection explains the “fit” between organisms and their environment 1 2 3 Natural selection – due to the interaction of organisms and their environment and results in organisms that have increased abilities to survive or reproduce in their environment Artificial selection – due to intentional human control of the survival and reproduction of organisms and results in organisms that suit a human desire – also know as “selective breeding” Natural selection produces “descent with modification” Natural selection operating in different populations of the same species produces divergence of lineages and potentially different - speciation species p p Extinction – the failure of a lineage to persist 4 Continued divergence multiplies lineages and sometimes produces “major transitions” in form and function. Descent with modification appears to have produced the full range of biological diversity – the “tree of life” Evolutionary biology is a scientific endeavor that studies the patterns and processes of evolution Two general approaches are used by evolutionary biologists • empirical • theoretical h i l Empirical studies • observational • fossils provide information on past evolution • comparative anatomy and molecular studies – similarities provide information relationships of lineages and can provide evidence of past selection • behavioral and ecological studies document factors that influence past and future evolution • manipulative experimental studies •… 5 Read: • Mikkelsen’s studies of human and chimp molecular evolution • Khatovich’s studies of differences in gene expression in humans and chimps A manipulative experiment Pizzari’s sperm competition experiment in chickens • used existing mating system in chickens • made predictions about how male chickens should respond to change in amount of sperm competition • manipulated amount of sperm competition and compared results with expectations 6 100 Offspring Number (N) Offspring Number (N) Theoretical approaches • mathematical models or logical reasoning allow predictions about the outcome of environmental change • e.g. sex ratio selection and evolution (later) • e.g. parental investment theory 80 60 40 20 0 0 5 10 15 Parental Investment (size) 20 80 60 40 20 0 25 05 0.5 0 5 10 15 Parental Investment (size) 20 25 0 5 10 15 Parental Investment (size) 20 25 0 5 10 15 Parental Investment (size) 20 25 0.5 0.4 Offspring Fitness Offspring Fitness 100 0.3 0.2 0.1 0.4 0.3 0.2 0.1 0 0 0 5 10 15 Parental Investment (size) 20 25 1.6 3 1.4 Parental Fitnesss Parental Fitness 2.5 2 1.5 1 0.5 12 1.2 1 0.8 0.6 0.4 0.2 0 0 0 5 10 15 Parental Investment (size) 20 25 7 8