2. Evolution Unit 12 p. 7-14, 417-428, 499-515

3. Darwin and Natural Selection  Beagle Expedition: found unique species that looked similar to species from other parts of the world.  Noticed changes in form among members of the same and closely related species.

4. Voyage of the HMS Beagle

5. The Origin of the Species  On The Origin of Species by Means of Natural Selection Nov. 1859 Charles Darwin  He avoided the term "evolution”  “light will be thrown on the origin of man and his history".  "endless forms most beautiful and most wonderful have been, and are being, evolved."

6. Natural Selection  Natural selection: mechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce, and pass these variations on to the next generation (those with less favorable traits are less likely to survive).  Referred to by Darwin as “decent with modification”

7. Evolution of Humans  The Descent of Man, and Selection in Relation to Sex Charles Darwin 1871  Darwin outlined sexual selection to explain the evolution of humans

8. 4 Tenets of Natural Selection  All populations have genetic variation.  The environment presents challenges to successful reproduction.  Individuals tend to produce more offspring than the environment can support.  Individuals that are better fit their environment tend to live longer, reproduce more, and spread their genes throughout the population.

9. Darwin’s 4 Facts  Exponential Growth of Populations  Factors will prevent Exponential Growth(Steady State)  Variability among species  Traits are inheritable (NOT AQUIRED)

10. Darwin’s 2 Inferences  Competition for resources  Individuals most fit for their environment will survive.

11. Natural Selection  Natural Selection is accepted as the driving force for evolution. What is a the difference between a scientific hypothesis, law, and theory? What is a the difference between a scientific hypothesis, law, and theory?

12. Hypothesis, Theory, Law  Hypothesis- explanations that are testable through experimentation or observation.  Theory- comprehensive explanation of facts, laws, and reasoning that is supported by many observations and multiple lines of evidence. A working model of a natural phenomena. Theories are accepted by the scientific community. (ex. Modern Atomic Theory, Cell Theory, Theory of Evolution)  Law- short, usually mathematical, explanation of a scientific relationship. (ex. Law of Conservation of Matter/Energy, Gas Laws, Law of Gravity, Thermodynamics, Newton’s, Kepler’s)

13. Evolution Terms  Species- group of organism capable of breeding to produce fertile offspring.  Population- a particular species in a given area that is interbreeding.  Changes happen to individuals, populations of species evolve.

14. Evolution Terms  Reproductive Fitness- Advantage of a particular genotype to survive and reproduce at a greater rate.  Fitness is specific to a particular environment. (Consider both the biotic and abiotic environment).  As the environment changes, so do the fitness values of the genotypes.  Fitness is a property of a genotype, not of an individual or a population.  Individuals with the same genotype share the same fitness within the same environment.  Fitness is measured over one generation or more.  The concepts of fitness and adaptation are relevant ONLY in a particular ecological context. There is no such thing as fitness in an absolute sense.

15. Evolution Terms  Adaptation- a genetically determined characteristic that improves an organism’s ability to survive and reproduce in a particular environment.  Adapt- the evolutionary process by which organisms become better suited to their environments

16. Evolution Terms  Structural Adaptations: Can change the size and/or shape of a body part Can change the size and/or shape of a body part For example: thorns, wings, mimicry (copy the appearance of another species), camouflage (blend in with environment) For example: thorns, wings, mimicry (copy the appearance of another species), camouflage (blend in with environment) Change within a population over time (anywhere from 100 years to millions of years) depending on type of adaptation, rate of reproduction and environmental factors Change within a population over time (anywhere from 100 years to millions of years) depending on type of adaptation, rate of reproduction and environmental factors  Physiological Adaptations: Help populations overcome chemicals they encounter (antibiotics, pesticides, herbicides, etc) Help populations overcome chemicals they encounter (antibiotics, pesticides, herbicides, etc) Develop rapidly (example: bacterial resistance to penicillin) Develop rapidly (example: bacterial resistance to penicillin)

17. Evolution Terms  Genetic variation- small differences among individuals within a population  Genetic Variation must be present for evolution to occur.  Polymorphic- the presence of two or more alleles (variations) of a gene in a gene pool.

18. Sources of Genetic Variation  Mutation/Translocation- change in DNA sequence that can slowly introduce new alleles to a population (can be harmful, beneficial or have no significance)  Crossing Over- exchange of homologous chromosome segments.  Independent Assortment- random alignment of chromosomes.  Sexual Reproduction (fertilization)- combination of alleles of two individuals  Immigration- incoming alleles to a gene pool

19. Mutation = a heritable change in the nucleotide sequence of DNA, resulting in an alteration in the products coded for by the gene. (about 0.5% of DNA bases are variable)

20. Consider how the amount of genetic divergence (change) forms a continuum: Microevolution Macroevolution small changes large changes Microevolution = adaptation Macroevolution = speciation

21. Microevolution vs. Macroevolution  Microevolution- changes within a species that can occur over dozens or hundreds of generations.  Macroevolution- evolution over long periods of time that involve origin of new species.

22. Microevolution  Population genetics- change in the genetic composition of populations. Uses Mendel’s Law of inheritance, Biochemical analysis of genes and proteins, and Mathematical models to understand microevolution. Uses Mendel’s Law of inheritance, Biochemical analysis of genes and proteins, and Mathematical models to understand microevolution. Gene Pool- all the genes of a population of organisms. (refers to a single population, not the entire species) Gene Pool- all the genes of a population of organisms. (refers to a single population, not the entire species)

23. Hardy-Weinberg  Idealized mathematical model of allele frequencies in gene pools.  Hardy Weinberg uses allele frequency to calculate the genotype frequency.  Assumptions Organism is diploid Organism is diploid Generations do not overlap Generations do not overlap Population size is large Population size is large Mutation is negligible Mutation is negligible Random Sexual Reproduction Random Sexual Reproduction Migration is negligible Migration is negligible Natural Selection does not operate Natural Selection does not operate  Under these assumptions, allele frequencies remain stable over time.

24. Hardy-Weinberg  p- frequency of one allele  q- frequency of another allele  p 2 - frequency of homozygous p genotype  2pq- frequency of heterozygous genotype  q 2 - frequency of homozygous q genotype  p + q = 1  p 2 + 2pq + q 2 = 1

25. Mechanisms for Evolutionary Change  Natural Selection  Artificial Selection  Gene Flow  Genetic Drift  Founder Effect  Genetic Bottleneck

26. Microevolution in Large Populations  Natural selection is the main factor that changes the gene pool of large populations.  Peppered Moth (p.423)  Malaria/ Sickle Cell Anemia (p.423-424) http://www.pbs.org/wgbh/evolution/library/01/2/l_01 2_02.html http://www.pbs.org/wgbh/evolution/library/01/2/l_01 2_02.html http://www.pbs.org/wgbh/evolution/library/01/2/l_01 2_02.html http://www.pbs.org/wgbh/evolution/library/01/2/l_01 2_02.html  Gene Flow  Mutation

27. Gene flow = introduction or loss of new alleles into the population through immigration or emigration.

28. Microevolution in Small Populations  Genetic Drift  Founder Effect  Inbreeding  Genetic Bottleneck (Population Bottleneck)  Inbreeding Depression

29. Genetic drift = random shifts in allele frequencies in small populations

30. Founder’s Effect  Small number of individuals of a large populations migrate and start a new population.  Gene pools of new population can change greatly from the original population if the new population is small.  Causes a loss of genetic variation.  Can cause inbreeding- the rise of homozygosity within a population.

31. Genetic Bottleneck  The number of organisms in a population is drastically reduced (hunting, disease, loss of habitat, etc.)  Large populations can become inbred  Inbreeding can lead to the increase of the frequency of harmful recessive alleles in the gene pool.  Inbreeding Depression- increased homozygosity of a population leads to reduction os fertility and survival.

32. Speciation = Origin of a new Species  Species = group of organisms that look alike and have the ability to interbreed and produce fertile offspring in nature  Speciation occurs when Interbreeding is prevented Interbreeding is prevented Production of fertile offspring is prevented Production of fertile offspring is prevented

33. Speciation  Species organisms that can reproduce successfully.  Genetic Isolation causes speciation- populations gene pools become so different, they can no longer interbreed.  Prezygotic Isolation mechanisms keep members of different populations from fertilizing each other.  Postzygotic isolation mechanisms keep populations from producing viable or fertile offspring.

34. Prezygotic Isolation  Geographic Isolation- barrier (mountains, canyons, oceanns, etc.) keep members from meeting each other.  Ecological Isolation- populations do not crossbreed because their habitats differ adaptive radiation.  Behavioral/ Reproductive isolation- differences in courtship and/or mating season  Chemical isolation: sperm may not be attracted to an egg or may not penetrate the egg when they find it.

35. Adaptive Radiation  Adaptive radiation is rapid evolutionary change characterized by an increase in the morphological and ecological diversity of a single, rapidly diversifying lineage. Phenotypes adapt in response to the environment, with new and useful traits arising. This is an evolutionary process driven by natural selection.

36. Natural Selection leads to Adaptive Radiation and Speciation

37. Geographic Isolation

38. Postzygotic Isolation  Zygotes may not develop properly.  Odd chromosome numbers in hybrids (mules, ligers, zonies, etc.) complicate meiosis.  Plants can become polyploid, making mating difficult with plants having the parental # of chromosomes.

39. Pace of Evolution  Gradualism- speciation can occur at a slow but constant accumulation of changes.  Punctuated Equilibrium- species experience long periods of no change between short bursts of change. Has been proven by evolution of E coli bacteria in nutrient-poor growth conditions. Has been proven by evolution of E coli bacteria in nutrient-poor growth conditions. Explains gaps in the fossil record between related species, short transition leads to little chance for fossils. Explains gaps in the fossil record between related species, short transition leads to little chance for fossils.

40. Types of Natural Selection  Stabilizing Selection - favors average traits (average sized spiders fair better than both large and small)  Directional Selection - favors one extreme of a trait (the longer the beak the better)  Disruptive Selection - favors both extremes of a trait (intermediate at disadvantage - often eliminated)

42. Types of Evolution  Divergence (ex: adaptive radiation); Single populations splits to adapt to different environments Single populations splits to adapt to different environments  Convergence Unrelated species become similar as they adapt to a similar environment. Unrelated species become similar as they adapt to a similar environment. Analogous structures Analogous structures Same use, different formSame use, different form Not evidence of a common evolutionary ancestorNot evidence of a common evolutionary ancestor

43. Evidence for Evolution  Fossils  Anatomical relationships  Embryological development  Genetic comparisons

44. Fossil Record  Fossils can help provide a record of the history of life and shows evolutionary change. Shows physical record or extinct organisms. Shows physical record or extinct organisms. Shows organisms before and after divergence of species. Shows organisms before and after divergence of species. Shows the rate of evolutionary change. Shows the rate of evolutionary change.  Radiometric dating- use of the ratio of radioactive isotopes, can be used to put a relative date on a fossil.  The record is incomplete - there are large gaps - therefore each and every step of evolution can not be followed.  Paleontologists look for intermediate species to provide a step by step sequence of evolution.

45. Anatomical Comparisons  Homologous structures Same form, different use Same form, different use Indication of common evolutionary ancestor Indication of common evolutionary ancestor  Vestigial structures Evolutionary remnants of structures that were important in a past ancestor Evolutionary remnants of structures that were important in a past ancestor

46. Embryological Development  There are noted similarities between the embryological development of all vertebrates (fish, chicken, rabbit, human, etc) Presence of gills and tails in all supports evidence that gill-breathing vertebrates preceded air-breathing, terrestrial species Presence of gills and tails in all supports evidence that gill-breathing vertebrates preceded air-breathing, terrestrial species

47. Genetic Comparisons  All living things use DNA.  All living things use the same genetic code.  Can show relationships between species (human and chimpanzee DNA are 99% identical and are closer than chimpanzees are to apes)  Can help reveal when species diverged from their ancestral types