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Chapter 2

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Zachariah Campbell

CHAPTER 2 Cladogram: a graph that shows the relative time of origin of various closely related groups  Each branch point in a cladogram distinguishes animals positioned before that time point from animals positioned after it by one or more physical or behavioral traits. In past 5-8 million years, hominids (humanlike ancestors) diverged from the ape lineage by acquiring characteristics that diverged from the apes. This included:  Being taller with less height differences between males and females.  They were bipedal with long legs, being able to travel large distances  Changes in hand structure allowed for tool use  Changes in tooth structure and reduction in jaw size allowed for more varied diet  The brain increased three times its size Species Comparison Why Study Nonhuman Animals? There are similarities between humans and chimpanzees  Physical stature and facial features/expressions  Behavioural traits in common – social living, tool use, omnivorous foraging Rats are good because their brains are a lot like humans. Slugs are studied how neurons connect to behaviour because slugs have a simple nervous system. Fruit flies are useful to study how genetic basis of behaviour because flies with altered nervous systems can be bred quickly. Genes: functional units that control the transmission and expression of traits from one generation to the next Questions Addressed by Studying Nonhuman Animals Understanding Brain Mechanisms Cross species comparisons are meant to study basic mechanisms of brain structure.  Even though fly and mammal eyes are vastly different, studying them has found that the same development is necessary in both. o Similar genes called homeobox genes dictate body segmentation in both. o The differences in eye structure are due to mutations and in the way that the products of the mutated genes interact with the products of other genes. Designing Animal Models Research animals substitute for humans because similar principles are assumed to underlie the emergence and treatment of a disorder in humans and nonhumans alike. Ideally, researchers want to produce the disorder in animals, manipulate many variables, and formulate a treatment. Parkinson’s disease models have been developed in mice, rats, and monkeys.  Def.: associated with aging in humans. The symptoms include rigidity that impedes voluntary movement, balance problems, and tremors of the head, hands, and limbs. Currently, there is no cure. Describing Evolutionary Adaptations Comparative research on how the mammalian brain and behaviour progresses in three ways: 1. All mammalian species evolved independently from some common ancestor 2. Because mammalian species are related, commonalities tell us what humans inherited from the common ancestor 3. Differences in brain and behaviour of different species tell of how species and individual differences arose Tool use is important to humans but is not just found in humans and primates. It has been found in birds with larger than average cerebellums.  Evolution and elaboration of the human cerebellum is associated with development of tool use Use of a Quasi-Experimental Sequence Quasi-Experimental Sequence: a hypothetical sequence of animals that represent consecutive stages in evolutionary history  Researchers assume that the evolutionarily older present-day animals resemble a common ancestor closely enough to stand for it. When this sequence is made for the primate lineage, a comparison of brain and behaviour of the animals in the sequence reveals a correspondence between new structural developments and new behaviours. Human Origins Hominid Evolution Humans are the only living survivor of the hominid branch. The 3 general lines of research for reconstructing human evolution are archeological, biochemical and genetic, and behavioural. Archeological Research Using the ages of sendiments found in fossilized bones, researchers can create a lineage of hominid species.  Skull casts = insight into brain structure  Examination of habitat gives cues to behaviour  Reconstruction can approximate the appearance of a hominid body Neandrathals used tools, lived in family groups, made music, and buried their dead. They probably had a language and religious beliefs. Biochemical and Genetic Research The amino acid sequence of a cellular protein in one species can be compared with the amino acid sequence of the same protein in another species. A change in one amino acid may occur on average about once every million years, and so the differences between proteins provide a molecular clock that can be used to compare the ages of different species. The relatedness of different species can also be determined by comparing their deoxyribonucleic acid (DNA), the genetic material in the nucleus of the cell. Genes are segments of DNA that specify what proteins a cell should make. Each gene is a long chain of four kinds of nucleotide bases. Through mutations, the sequence of bases can change to some extent and still leave a functional gene. Behavioural Research Comparative behavioural research gives evidence for theories about human evolution. Stages of Human Evolution Investigators agree that four general steps led from a chimpanzee- like common anc
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