Exam 3, Chapters 6 & 7 PDF

Chapter 6 Key Terms & Ideas Convergent evolution: shows similarities in behavior/structure among unrelated animals due to adaptations to similar environments. Homoplasy is the resemblance between features (such as body shape) due to convergent evolution (sharks and dolphins). Homology is a similarit...

Chapter 6 Key Terms & Ideas Convergent evolution: shows similarities in behavior/structure among unrelated animals due to adaptations to similar environments. Homoplasy is the resemblance between features (such as body shape) due to convergent evolution (sharks and dolphins). Homology is a similarity based on common ancestry. Analogy is a similarity based on function (human hand + elephant’s trunk). Genetics are the study of the mechanisms of inheritance that began with Mendel & DeVries. Linnaeus’ system of classification: each species has 2 names. - Genus: group of individuals that resemble each other - Species: group of individuals that can produce fertile offspring Phylogeny is a history of a particular group of organisms and may look like a family tree. Taxonomy is the classification of organisms. Reasons to Study Species Outstanding features, comparison, treatment of disease, brain development. Two Methods Used to Study Evolution of the Brain Endocast: the use of fossil skulls to make a cast of the brain. Study living animals: choose species that are similar to ancestral forms. *Change over time is not a linear evolutionary sequence! Studying the Brain in Evolution Encephalization factor: a measure of brain size relative to body size. Brain weight relative to body size varies between and within classes. Primates: Brain regions that developed later are enlarged, and more important. The medulla is smaller, the cerebellum remains the same size, and the cortex becomes larger. All mammals have a 6 layered cortex, also called a neo cortex. Reptiles have 3 cortical layers. Hominin: Species after splitting from chimp line, brains enlarged rapidly in our recent evolution. Australopithecines: Hominins that made and used tools. Ability to use tools reduced the necessity for large jaws, which increased space for the brain. 3.5 million years ago: Bipedalism followed by hands and teeth. 250,000 years ago: Cities, agriculture, art. Homo erectus turned into homo sapien. Large brain costs and benefits Costs: Long gestation period and small birth canal. Prolonged dependence on parents. Complex genes that are vulnerable to mutation. Benefits: Innovative and flexible behavior. Use of tools. Social learning. Social brain hypothesis (Dunbar): Group size is limited by brain size. Natural selection does not account for the social brain hypothesis in brain size. Instead, Miller suggested sexual selection accounts for natural selection.