lectures 1-7 studied for midterm

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University of Toronto Scarborough
Michael Schillaci

ANTB14- LECTURE 1 Charles Darwin, who is credited with the discovery of the principal of natural selection in 1838, was born in England in 1809. He died in 1882. Darwin was part of an expedition to map the coast of South America between 1831 and 1834-35 aboard the HMS Beagle. As the Naturalist for the expedition, Darwin was in charge of collecting and describing plant and animal specimens encountered on this expedition. During his long journey, after observing incredible plant and animal diversity, as well as fossils, he became interested in the question of how species come about. He was convinced that species came about by slow change. Just HOW species changed was still a mystery. In 1838, shortly after returning home from his journey, Darwin read Thomas Malthus essay titled An Essay on the Principal of Population. In this essay Malthus, among other things, presents the notion that populations can increase in size exponentially while food supplies remain relatively stable. This means that eventually a population will increase to the point that there is not enough food or resources. This notion would become the cornerstone of Darwins theory of evolution. Darwins Theory: 1. The ability of a population to expand is infinite, but the environments ability to sustain that population is finite. 2. Organisms within the population vary, and this variation affects the ability of individuals to survive and reproduce. 3. This variation is transmitted from parents to offspring. Darwins theory is based on three postulates or concepts. The book summarizes these as: 1) A struggle for existence 2) Variation in fitness 3) Inheritance of variation When resources are in demand (i.e. when the environment cant support the existing population), a struggle for existence occurs within the population. Some individuals will possess physical or behavioral traits that allow them to better compete for resources allowing those individuals to survive and reproduce. These individuals pass these traits along to their offspring. Traits that are advantageous within the environment are therefore retained within the population, while disadvantageous traits eventually disappear. This process is termed NATURAL SELECTION. These advantageous traits are termed ADAPTATIONS. Example: The Finches of Daphne Major (Galapagos Islands) Studied by two Princeton biologists. www.notesolution.comThe finches (approximately 1500) on this island are trapped every year and measured, their behavior was observed, and environmental factors such as rainfall and temperature were monitored. The finches subsisted primarily on seeds. Shortly after their study began there was a severe drought, at which time the plants began producing fewer seeds. Soon the finches had eaten all of the softer easy-to-process seeds leaving only the larger, more difficult- to-process seeds. The shallow-beaked birds were forced to process larger seeds. During this nearly 2-year drought the population of finches dropped from 1200 to 180. A schematic diagram of how directional selection increased mean beak depth among medium ground finches on Daphne Major. Birds with deeper beaks were able to process the larger seeds and were more likely to survive and reproduce. It is important to note that even birds with deeper beaks died during the drought. The drought can be termed a selection event. This event selected for larger beaks, which was an adaptation to the new condition. Because a greater proportion of those birds with deeper beaks survived and reproduced, the average beak depth in the population increased. When the average of the population increases or decreases this is termed DIRECTIONAL SELECTION. The average beak depth in the population of medium ground finches on Daphne Major increased during the drought of 1975-1978. Because having a largerdeeper beak requires more calories when developing there are disadvantages to having a deep beak. The Daphne Major finches with deeper beaks experience greater juvenile mortality. This disadvantage is offset by the reduced mortality and greater probability of reproduction after the juvenile period. Beak size increases until the disadvantages outweigh the advantages. At this point the average beak size in the population is selected for and the birds with an average size beak are the most likely to survive and reproduce. Parents with deeper-than-average beaks tend to have offspring with deeper-than-average beaks. This is consistent with Darwins postulate that variation is passed down from parent to offspring. LECTURE 2 Diverse Order: diversity in diet among taxa, diversity in social organization, diversity in daily activity patterns Why are ANTHROpologists interested in nonhuman primates? Primates are of interest to anthropologists because they can help us to study human evolution through the principal of homology, because we share a www.notesolution.comcommon ancestor, and through analogy, because human and nonhuman primates are similar morphologically, physiologically, and even behaviorally. Primates is a diverse order. This diversity includes diet: some primates eat primarily leaves, while others rely on fruit, or insects, or even sap. Diversity in social organization: some primate taxa live in multimale groups, while others live in single male groups Diversity in activity patterns: some are active during the day (diurnal), others are active at nigh (nocturnal). What makes a primate: opposable big toe or thumb, flat nail on at least one digit, reduced olfactory apparatus, stereoscopic vision, large brain, postorbital bar Prosimians (or lesser primates) have wet noses (strepsirhine), an open orbit, and a higher level of olfaction. Anthropoids (higher primates), have dry noses (haplorhine), and closed orbits. www.notesolution.com
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