1. Natural selection

2. Charles Darwin Born February 12, 1809 Shrewsbury England Medical School (1825-1827) –Darwin is 16 Years Old Cambridge (1827-1831) Clergyman Naturalist of H.M.S. Beagle Beagle Departs from Plymouth, England on December 27, 1831 –Darwin is 22 Years Old

3. H.M.S. Beagle

4. Route of the H.M.S. BEAGLE

5. timeline January 1832 Santiago, Cape Verde Islands “Seashells” April 1832 Rio de Janeiro, Brazil “Entomological Specimens” August 1832 Patagonia Coastline “Useless Junk (Fossils)” March 1833 Falkland Island, Port Louis “Comparing Fossils” September 1835 Galapagos Islands, “Discovering Diversity” October 1836 Falmouth England, “Journey Ends” 4Y9M5D March 1837 London Zoo “Discovery of Darwin’s Finches” November 1859 Published “Origin of the Species” 1930’s-1940’s Evolutionary Synthesis “Mendel and Darwin”

6. Theory of Natural Selection 1.Organisms produce more offspring than can survive. 2.In any given population, variations exist. 3.Individuals with certain “useful” or beneficial variations survive and pass on their variations to the next generation. 4.Over time, offspring with “beneficial” variations will make up most of the population.

7. Natural Selection Darwin used his collections and observations to identify a mechanism for change in populations. Darwin called this mechanism: NATURAL SELECTION

8. Natural Selection Science’s “best guess” on how populations change over time. Natural Selection is based on the following scientific evidence. Structural Adaptations Physiological Adaptations Fossils Anatomy Embryology Biochemistry

9. Structural Adaptations Structural adaptations are changes in an organism’s appearance Structural Adaptations usually develop over a long period of time Defensive Adaptations Large Teeth and Claws, Speed and agility, chemical Protective Adaptations Camouflage, Mimicry, Speed, Chemical, Quills, Spines Specialized Height, Strength, “Specialized Anatomy”

10. Physiological Adaptations Changes in an organism’s metabolic processes. Can occur over a relatively short period of time. Examples –Bacteria –Pesticides –Herbicides –Symbiotic Relationships (Clown Fish and Sea Anemone)

11. FOSSILS FOSSIL EVIDENCE: Provide record of early life Show how changes occurred within most populations and species. FOSSIL SHORT COMINGS –Incomplete for many species –Inferences [However, DNA can support these inferences]

12. ANATOMY CONVERGENT EVOLUTION Organisms share same function, but not the same form, come from different ancestral lineages. Analogous Structures –Similar structural functions but do not share a common evolutionary origin. Similar in function but not arrangement –Insects vs. Birds

13. ANATOMY DIVERGENT EVOLUTION Species that were once similar Homologous Structures –Structural features with a common evolutionary origin Can be similar in arrangement and function. –Forelimbs of human, cat, whale, bat Vestigial Structure –Body structure in a present day organism that no longer serves its original purpose. Feature is still inherited, although it no longer serves it’s purpose. –Eye balls present in blind cave salamander

14. Embryology Early Embryonic development, all embryo’s have a tail and pharyngeal pouches.

15. Biochemistry Organisms share same biochemical molecules –DNA, ATP, ENZYMES, AMINO ACID SEQUENCE Organisms that are biochemical similar have fewer differences in their amino acid sequence and are believed to be more closely related or share a common ancestor. Phylogeny: Construction of “family trees” using DNA and RNA

16. THE EVIDENCE Scientist use: –Adaptations Structural Physiological –Fossils –Anatomy Micro and Macro –Embryology –Biochemistry DNA, RNA, Amino Acids

17. Applying Natural Selection SPECIATION: Process in which a new species arises from a formerly interbreeding population. –Cause Geographic Isolation Reproductive Isolation –Rate Fast—Punctuated Equilibrium »Periods of speciation occurs quickly within a long period of genetic equilibrium. Slow—Gradualism »Species originate through a gradual change of adaptations.

18. Applying Natural Selection Populations, Not Individuals, Evolve –Variations arise from mutations –Alleles represent the genetic variation in a population –The Gene Pool is the all of the different alleles in a given population. –The percentage of any one allele in the gene pool is called the Allelic Frequency. –If the frequency of an allele remains constant we refer to that as Genetic Equilibrium.

19. Applying Natural Selection: Directional Selection Natural Selection Favors One Extreme Variation of a Trait Example: Birds with varying sizes of beaks, after a drought, the large beak birds have selective advantage

20. Applying Natural Selection: Disruptive Selection Individuals with either extreme trait are selected for. Example: Tourists in the desert like to pick up a souvenir from their travels, they pick up the medium spine cactus. Leaving the “homelier” low spine and avoiding the “prickly” high spine cactus, both of which have the selective advantage.

21. Applying Natural Selection: Stabilizing Selection Natural Selection Favors average individuals in a population. Example: Birth weight in humans is highly variable, however, a child that is of average weight has a higher chance of being born and of good health, as to mature and reproduce. Nature selects against the extreme phenotypes.

22. Natural Selection is currently the best theory scientists have to explain the vast diversity of life on Earth and how populations change over time. In science, nothing can ever be proven as fact, there are no facts in science, only “best guesses”. These best guesses are based on current, verifiable, and testable evidence. We call a collection of evidence that fails to disprove a hypothesis—a theory. In fact, science can only be used to disprove not prove anything.