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EVOLUTION Change in allele frequencies over time.

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Presentation on theme: "EVOLUTION Change in allele frequencies over time."— Presentation transcript:



3 EVOLUTION Change in allele frequencies over time

4 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


6 Darwin’s Findings Varying characteristics within a species Species held characteristics which benefitted their survival Offered Idea of “Natural Selection” Darwin's Darkest Hour

7 Observation #1 All Species have such great potential fertility that their population size would increase exponentially if all individuals that are born reproduce successfully.

8 Observation #2 Populations tend to remain stable in size, except for seasonal fluctuations

9 Observation #3 There are limited resources in the environment. There is a struggle for survival. Competition for food, mates, space is the key.

10 Observation #4 Individuals of a population vary extensively in their characteristics, no two individuals are exactly alike.

11 Observation #5 Much of Variation is heritable These favorable traits persist in the population and will become more frequent.

12 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.


14 Explain the Theory of Natural Selection? Interpret the saying “Survival of the Fittest”


16 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

17 Men of Evolution

18 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


20 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!!

21 Darwin’s Influences CURVIER AND LYELL – argued that species change over time based on geological and fossil findings CORRECT!!





26 Artificial Selection Canis lupus Canis familiaris



29 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

30 The Fossil record… OBSERVATION




34 Warning Colors Antipredator Defense

35 Comparative Anatomy Vestigial Structures –Inherited structure from ancestor, however no longer uses structure

36 Homologous Structures Similar structures inherited from common descent, however function changed to fit environment Same Limb Orientation – Different Functions

37 Analogous Structures


39 Population Genetics Study of the complex behavior of genes in populations, based upon the variation amongst populations in nature Individual Population Which Evolve ?

40 Formation or Elimination of a species Small changes over the course of time which impact/change species


42 Gene Pool Summation of all alleles in a population If Allelic Frequency does not change = Genetic Equilibrium = No Evolution Disruption of Genetic Equilibrium initiates process of evolution

43 Mutations –Radiation –Chemicals –Chance Genetic Drift –Only certain members of a population reproduce and pass on traits –Allele Frequencies become drastically different Geographic Isolation



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