1. EVOLUTION Transformation of the Biological Paradigm

2. Evolution Charles Darwin BUT, the history of Evolutionary Thought pre-dates Darwin considerably…

3. The Aristotlean-Christian World View Aristotle (350 BC) Observes Life’s Complexity & Suggests a “Hierarchy of Life” Complexity

4. Naturalists begin to find problems Some organisms were not fitting properly into the hierarchy. Due to Variations –Viewed as imperfections of an idealized form. –Which characteristics of an organism are most important for placing it in the hierarchy? –How much variation should be viewed as normal within a species?

5. Suggested that CHANGE in organisms took place by “Inheritance of Acquired Characteristics”. –Characteristics acquired during an organism’s life were passed on to offspring. –Giraffe Necks became longer and longer as each generation stretched higher into the trees for food. Problem… Jean-Baptiste de Monet de Lamarck

6. Lamarck’s hypothesis was never supported by experiments & has long since been DISPROVED. Why? …An environmentally-induced phenotype cannot be passed on to the next generation…only genotype can! Lamarck still remembered for this mistaken hypothesis, but still contributed many innovative ideas. Jean-Baptiste de Monet de Lamarck

7. Charles Darwin 5 year voyage (1831-1836) Lots of DATA! 1. Geologic He saw first hand what Hutton had suggested (Gradualism), and agreed with Lyell’s premise that the Earth must be very old. He examined many fossils – some resembling modern (current) organisms, but not exactly. –Saw the possibility for Descent with Modification (modern forms having descended from now-extinct forms), and for organisms changing over time.

8. Charles Darwin …DATA 2. Biogeography He found similar organisms in far-reaching places, but in similar habitats. –Suggested that organisms may be adapting to the same types of environment, despite the distance between them. He found slight variations in organisms found in slightly different habitats (but separated from each other … Finch Bills, Tortoise Necks, etc.) –Suggested that a common ancestor gave rise to the different varieties, which each adapted to slightly different environments.

9. Charles Darwin Returned from the voyage and…PUBLISHED! Saw that adaptation to environment was indeed real, and eventually formulated a mechanism for it, but… –He did not want to jeopardize his scientific status, so didn’t publish it. Along came Alfred Russel Wallace…

10. Alfred Russel Wallace (1823-1913) Naturalist Studied and admired Darwin’s work. Wrote Darwin to see what he thought about a hypothesis regarding a mechanism for adaptation to the environment. This hypothesis was virtually the same as Darwin’s (unpublished) ideas about how change could take place!

11. Darwin & Wallace 1858 -- Presented their hypotheses at a meeting of the Linnaean Society (London): "The Variation of Organic Beings under Domestication and in their Natural State" "On the Variation of Organic Beings in the State of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and true Species"

12. Darwin Later (1859) published his famous essay: “I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.” - Charles Darwin, The Origin of Species

13. Evolution by Natural Selection: 5 KEYS 1.VARIATION Variation is inherent in populations of organisms (members of a population are not all the same). This Variation is Heritable – able to be passed from generation to generation. Elaphe obsoleta

14. 2.More offspring are born than survive. Differential reproduction and survival. “Survive” = Live long enough to reproduce. Evolution by Natural Selection: 5 KEYS

15. 3.Differences occur between surviving offspring and those not surviving. Advantageous Varations = Certain characteristics found in surviving offspring that afford them a survival advantage. Sometimes called “Adaptations” (but this implies a goal, and Natural selection is NOT goal- oriented). Evolution by Natural Selection: 5 KEYS

16. 4.More individuals with advantageous adaptations occur in succeeding generations of organisms. Their variations are beneficial, therefore they survive & reproduce. Individuals without beneficial variation do not survive to reproductive age. Individuals Evolution by Natural Selection: 5 KEYS

17. 5.Results in a population that is well- adapted to its environment. Population as a whole is becomes fitted to its particular environment. Evolution by Natural Selection: 5 KEYS

18. NATURAL SELECTION “Struggle for Existence” –Limited Resources are available for a population, leading to Competition. Some survive, some don’t Sometimes this is random –The “Struggle” is for the resources, not as much direct competition between individuals.

19. “Survival of the Fittest” –The most FIT organisms survive & reproduce. –Fitness = how well an organism fits into its environment Securing resources Avoiding predators Finding food –What determines Fitness? Varies with organism, but ultimately….ENVIRONMENT This is always changing – what is most fit one month, may not be the next. NATURAL SELECTION

20. Environment is important! –In Artificial Selection, humans select for survival & reproduction. –In Natural Selection, nature selects for survival & reproduction. Habitat Climate Food & Shelter Availability Etc. NATURAL SELECTION

21. Not goal-oriented, no particular goal. –Environmental conditions are always changing. –Organisms’ needs are always changing. –Genotype is heritable, not phenotype. NATURAL SELECTION

22. Populations Evolve, NOT individuals. –Groups of individuals belonging to the same species and occupying the same given area, and being similar in form, behavior, and physiology. –Inheritance of acquired characteristics (Lamarck) does NOT occur. NATURAL SELECTION

24. Microevolution We know…. AllelesFormPhenotypeGenotype Adaptation to Environment, Evolution

25. Agents of Microevolutionary Change Processes that elicit changes in allele frequencies in populations: 1.Mutation 2.Gene Flow 3.Non-Random Mating 4.Genetic Drift 5.Natural Selection

26. 1.Mutation: A random heritable change in the DNA. –Only source of NEW alleles in a population. –Actually rather common! –Can be: Harmful (most – we’re complex), these do not remain in the gene pool and so are rare (selected against!). Neutral (many), masked, occur in genes not essential for survival, often passed on. Beneficial (rare – we’re complex), these are the key to better-adapting to changing environments. Agents of Microevolutionary Change

27. 2.Gene Flow: New individuals enter or exit a population (Migration). Introduces the possibility of new allele combinations. Often has a homogenizing (mixing) effect on the population – offering stability.

28. 3.Non-Random Mating: Mating & offspring production by individuals with specific phenotypes (genotypes). A.K.A. “Assortive Mating” or “Preferential Mating” (Not random). Results in accumulation of certain traits in the population (sometimes reduction of heterozygotes). Examples: Mate selection in white-tailed deer (“Sexual Selection”), tall Men & tall women, Agents of Microevolutionary Change

29. 4.Genetic Drift: Changes in allele frequency due to chance. Often due to natural disasters or major catastrophes. Especially in small populations. Bottleneck Effect: loss of certain alleles as a population dwindles, reduction in allelic diversity with a smaller and smaller population. Founder Effect: small population with a specific and limited gene pool is separated from the main population. Agents of Microevolutionary Change

30. 5.Natural Selection: Differential survival & reproduction of individuals in a population. 1.Stabilizing (the extremes of the population are selected against in favor of the average/most common) 2.Disruptive (the average/most common individuals of the population are selected against in favor of the extremes) 3.Directional (one extreme or the other of the population are selected against)

31. Agents of Microevolutionary Change 5.Natural Selection (Peppered Moths)