EVOLUTION Change in allele frequencies over time
Charles Darwin Sailed on HMS beagle to South America and South Pacific as a “Naturalist” Major findings on Galapagos Islands fueled Darwin’s curiosity and future theories 1859 published findings in book On the Origin of Species by Natural Selection
Darwin’s Findings Varying characteristics within a species Species held characteristics which benefitted their survival Offered Idea of “Natural Selection” Darwin's Darkest Hour
Observation #1 All Species have such great potential fertility that their population size would increase exponentially if all individuals that are born reproduce successfully.
Observation #2 Populations tend to remain stable in size, except for seasonal fluctuations
Observation #3 There are limited resources in the environment. There is a struggle for survival. Competition for food, mates, space is the key.
Observation #4 Individuals of a population vary extensively in their characteristics, no two individuals are exactly alike.
Observation #5 Much of Variation is heritable These favorable traits persist in the population and will become more frequent.
The Result: Differential reproductive success leads to change in favorable traits among generations. Each organism’s capacity to reproduce varies based on traits it possesses that make it suited or not suited to its environment.
Natural Selection Survival and Reproduction –Organisms possess alleles that generate traits which enable them to survive in their environment and increase their fitness Fitness = # of offspring produced Larger the Fitness = Greater chance of Survival
LaMarckian vs. Darwinian view LaMarck –in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring Darwin –giraffes born with longer necks survive better & leave more offspring who inherit their long necks
Darwin’s Influences LAMARCK –use or disuse of a characteristic would be passed down to the offspring WRONG!!! MALTHUS –organisms produce more offspring than can survive. Populations limited by environment. CORRECT!!
Darwin’s Influences CURVIER AND LYELL – argued that species change over time based on geological and fossil findings CORRECT!!
Evidence for Evolution 1.Paleontology –Examine fossils and compare to modern day organisms 2.Biogeography –Distribution of species –Unrelated species in different regions of the world resemble one another in similar environments 3.Embryology –Phylogeny (Developmental Similarities) 4.Comparative Anatomy –Comparison of anatomical structures to identify evolutionary relationships 5.Biochemistry –DNA studies shows relationships based on # of similar strands and chromosome numbers
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