1. Natural Selection Depending on what environment & conditions the organism is located, the following types of natural selection can occur: – Disruptive Selection – Stabilizing Selection – Directional Selection

2. The Bell Shaped Curve This is the standard distribution of traits in most populations.

3. Selection that favors both extremes over intermediates is called ____________ selection. 14. disruptive

4. Selection that favors the intermediate phenotype over the extremes is called _______________ selection. Stabilizing

5. Types of Selection Selection that favors individuals of one extreme phenotype usually during environmental change is called ______________ selection. 12. directional ANTIBIOTICS

6. IV. MECHANISMS OF EVOLUTION

7. Independent Assortment During Meiosis

8. Genetic variations in populations – Contribute to evolution Figure 23.1

9. Gene Pools and Allele Frequencies A population – Is a localized group of individuals that are capable of interbreeding and producing fertile offspring MAP AREA ALASKA CANADA Beaufort Sea Porcupine herd range Fairbanks Whitehorse Fortymile herd range NORTHWEST TERRITORIES ALASKA YUKON Figure 23.3

10. Let’s Go Swimmin’ The gene pool – Is the total amount of genes in a population at any one time – Consists of all gene loci in all individuals of the population

11. The total amount of genes within a population is called the ________ ________. 1. gene pool Eye color Blood type intelligence Diabetes Cysic fibrosis Caucasians

12. Two processes: – mutation and sexual recombination – Produce the variation in gene pools that contributes to differences among individuals

13. Mutation Mutations – Are changes in the nucleotide sequence of DNA – Cause new genes and alleles to arise Figure 23.6

14. Sexual Recombination In sexually reproducing populations, sexual recombination – Is far more important than mutation in producing the genetic differences that make adaptation possible

15. A. How variations provide material for natural selection Natural selection – Accumulates and maintains favorable genotypes in a population

16. Of all the agents that lead to microevolution the one that best adapts a gene pool to a changing environment is ______________ ______________. 11. naturalselection

17. Genetic Variation Genetic variation – Occurs in individuals in populations of all species – Is not always heritable Figure 23.9 A, B (a)Map butterflies that emerge in spring: orange and brown (b)Map butterflies that emerge in late summer: black and white

18. Three major factors that cause genetic variation and bring about most evolutionary change – Natural selection – Genetic drift – Gene flow

19. Natural Selection “Survival of the Fittest”

20. Genetic Drift Statistically, the smaller a sample – The greater the chance of deviation from a predicted result – Describes how allele frequencies can fluctuate unpredictably from one generation to the next – Tends to reduce genetic variation Figure 23.7 CRCRCRCR CRCWCRCW CRCRCRCR CWCWCWCW CRCRCRCR CRCWCRCW CRCWCRCW CRCWCRCW CRCRCRCR CRCRCRCR Only 5 of 10 plants leave offspring CWCWCWCW CRCRCRCR CRCWCRCW CRCRCRCR CWCWCWCW CRCWCRCW CWCWCWCW CRCRCRCR CRCWCRCW CRCWCRCW Only 2 of 10 plants leave offspring CRCRCRCR CRCRCRCR CRCRCRCR CRCRCRCR CRCRCRCR CRCRCRCR CRCRCRCR CRCRCRCR CRCRCRCR CRCRCRCR Generation 2 p = 0.5 q = 0.5 Generation 3 p = 1.0 q = 0.0 Generation 1 p (frequency of C R ) = 0.7 q (frequency of C W ) = 0.3

21. If a group of organisms within a large population become isolated, they may not represent the entire gene pool, thus leading to changes or ______________ __________________. 15. GENETICDRIFT

22. TWO TYPES OF GENETIC DRIFT Bottleneck Bottleneck & Founder Effect

23. This process can lead to a change in allele frequencies within a population? Bottleneck Effect

24. The Bottleneck Effect In the bottleneck effect – A sudden change in the environment may drastically reduce the size of a population – The gene pool may no longer be reflective of the original population’s gene pool Original population Bottlenecking event Surviving population Figure 23.8 A (a) Shaking just a few marbles through the narrow neck of a bottle is analogous to a drastic reduction in the size of a population after some environmental disaster. By chance, blue marbles are over-represented in the new population and gold marbles are absent.

25. Understanding the bottleneck effect – Can increase understanding of how human activity affects other species Figure 23.8 B (b) Similarly, bottlenecking a population of organisms tends to reduce genetic variation, as in these northern elephant seals in California that were once hunted nearly to extinction.

26. The Founder Effect The founder effect – Occurs when a few individuals become isolated from a larger population – Can affect allele frequencies in a population

27. B. The role of geographic isolation in speciation

28. SPECIATION Organisms that can interbreed and produce fertile offspring make up a species.

29. ISOLATING MECHANISMS 21. BEHAVORIAL ISOLATION

30. 22. Geographic

31. Some examples of geographic variation occur as a cline, which is a graded change in a trait along a geographic axis Figure 23.11 EXPERIMENT Researchers observed that the average size of yarrow plants (Achillea) growing on the slopes of the Sierra Nevada mountains gradually decreases with increasing elevation. To eliminate the effect of environmental differences at different elevations, researchers collected seeds from various altitudes and planted them in a common garden. They then measured the heights of the resulting plants. RESULTS The average plant sizes in the common garden were inversely correlated with the altitudes at which the seeds were collected, although the height differences were less than in the plants’ natural environments. CONCLUSION The lesser but still measurable clinal variation in yarrow plants grown at a common elevation demonstrates the role of genetic as well as environmental differences. Mean height (cm) Atitude (m) Heights of yarrow plants grown in common garden Seed collection sites Sierra Nevada Range Great Basin Plateau

32. Allopatric and Sympatric Speciation: A Summary In allopatric speciation – A new species forms while geographically isolated from its parent population In sympatric speciation – The emergence of a reproductive barrier isolates a subset of a population without geographic separation from the parent species

33. C. The importance of the environment in selecting adaptations Organisms must adapt to their environment to survive. This has led toward the following types of evolution: Convergent Evolution Divergent Evolution Adaptive Radiation

34. Sugar glider AUSTRALIA NORTH AMERICA Flying squirrel Figure 22.17 Some similar mammals that have adapted to similar environments – Have evolved independently from different ancestors 1 2.4 3.14 5.18 6 7.15 XX19 13.1710.169.12 8.11 12.193.84.165.146.7 XX 15.18 13.17 11.12 9.10 Figure 23.10

35. When different species began to look alike because they develop similar adaptations this is called _______________ ___________________ 24. CONVERGENT EVOLUTION

36. When a species moves into new environment and becomes less similar to the original species this is called _______ evolution. 25. DIVERGENT EVOLUTION

37. Adaptive Radiation Adaptive radiation – Is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities Figure 24.11

38. ADAPTIVE RADIATION

39. The Hawaiian archipelago – Is one of the world’s great showcases of adaptive radiation Figure 24.12 Dubautia laxa Dubautia waialealae KAUA'I 5.1 million years O'AHU 3.7 million years LANAI MOLOKA'I 1.3 million years MAUI HAWAI'I 0.4 million years Argyroxiphium sandwicense Dubautia scabra Dubautia linearis N

40. V. APPLICATIONS (PESTICIDE AND ANTIBIOTIC RESISTANCE) Evolution can be seen today : In Disease Resistance In Pesticide Resistance

41. A. Discuss the evolutionary selection of resistance to antibiotics and pesticides in various species. The Evolution of Drug-Resistant HIV – In humans, the use of drug selects for pathogens that through chance mutations are resistant to the drugs’ effects – Natural selection is a cause of adaptive evolution- the HIV adapts to the drugs. – Researchers have developed numerous drugs to combat HIV – But using these medications selects for viruses resistant to the drugs

42. So What! The ability of bacteria and viruses to evolve rapidly – Poses a challenge to our society – Puts us at risk of contracting a disease that can no longer be cured.

43. Artificial Selection In the process of artificial selection – Humans have modified other species over many generations by selecting and breeding individuals that possess desired traits Figure 22.10 Terminal bud Lateral buds Brussels sprouts Cabbage Flower cluster Leaves Cauliflower Flower and stems Broccoli Wild mustard Kohlrabi Stem Kale