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ECU BIOL 1050 - Mechanisms of Evolution
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BIOL 1050 Lecture 22 Outline of Last LectureI. EvolutionII. Evolution of populationsOutline of Current LectureI. BiogeographyII. Homologya. Molecular biologyb. Embryologyc. Anatomyd. Convergent evolution III. Mechanisms of Evolution Current LectureI. Biogeographya. The study of the geographical distribution of speciesb. Species resemble other species nearby even in very different habitats c. Ex. The honeycreepers of Hawaii have adapted to a wide range of habitats, yet still closely resemble a finch-like shared ancestor found nearly 2,000 miles awayII. Homologya. Similarity in structure due to common ancestryb. Homologies in:i. Molecular biology1. Evolutionary relationships can be studied by comparing the genes and proteins of different organismsa. The more similar, the more closely related2. Genetic similaritiesa. The longer two species have been evolving on their own, thegreater the number of genetic differences that accumulateii. Embryology1. Comparative embryology: the comparison of structures that appear during the development of different organisms2. Closely related organisms have similar stagesiii. AnatomyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. Comparative anatomy: the comparison of body structures between different species2. The similarities in the bone structure in the bone structure of the forelimbs of mammals demonstrates common ancestryiv. Convergent evolution1. Caution: presence of similar traits does not always indicate close relatedness2. Populations can have similar traits independently because they live in similar environments 3. Different starting materials come to perform the same function through convergent evolution 4. Ex. The similarity in shape between dolphins and sharks results fromsimilar adaptations to life as an oceanic predator of fish. However, sharks are more closely related to stingrays, and dolphins are more closely related to land mammals III. Mechanisms of evolutiona. 4 phenomena can cause a population’s allele frequency to change over time: i. Genetic drif1. A random change in the allele frequencies of a small population2. The change in allele frequencies is NOT related to the allele’s influence on reproductive success3. Genetic drif leads to fixation when an alleles frequency becomes 100% in a population. If this occurs, there is no longer genetic variation in the gene4. Small populations occur due to:a. Founder effect: when some individuals leave their main population and form a new small colony elsewherei. The new population will be dominated by the geneticfeatures present in the founding membersii. Frequency of alleles has been changed b. Bottleneck effect: when a population has ha a drastic reduction in size (e.g. a natural disaster)i. Occasionally famine or disease or rapid environmental changes may cause the deaths of a large, random proportion of the individuals in a population ii. The new population will be dominated by the geneticfeatures present in the surviving membersii. Gene flow due to migration1. When individuals mate with members of a different population so genes from 2 populations get mixed together2. Tends to reduce genetic differences between populations3. Gene flowa. Before migration: two populations of the same species exist in separate locations. In this exampleb. Migration: a group of individuals from one population migrates to the other populationc. Afer migration: the migrating individuals are able to survive and reproduce in the new population, both populations experience a change in their allele frequencies and experience evolution iii. Mutation1. May convert one allele to another that is already present in population2. May create a new allele that codes for a new proteina. If occurs in gamete, can be passed on and remain in population 3. Most mutations are harmful, but not all4. All genetic variation must initially come from mutation iv. Natural


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ECU BIOL 1050 - Mechanisms of Evolution

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