Exploring Evolution: Theories, Evidence, and Genetics

1. Statement of Inquiry: AGENDA • DO NOW: • EPA Time • (Obj 1) SWBAT Summarize the Theory of Evolution by Natural Selection • (Obj 2) SWBAT interpret the evidence of evolution with examples   DATE HERE 10 min {Insert entrance instructions here} For example: Enter the classroom silently and find your seat. Write down homework in your planner. Do Now Wait silently for instructions

2. Objective of the day • (Obj 1) SWBAT Summarize the Theory of Evolution by Natural Selection • (Obj 2) SWBAT interpret the evidence of evolution with examples. • .

3. Statement of Inquiry/IB Trait STATEMENT OF INQUIRY: Humans use their understanding of scientific principles to look for patterns and evidence using models that can change the way we understand our current world. IB TRAIT: KNOWLEDGEABLE, COMMUNICATORS and INQUIRERS

4. Read pg. 176 – 182 Answer question on the side in notebook. Write the question and answer!! I will be coming around and checking off your posters as you read. Please have them out. Warm Up

5. Identify and summarize the 3 modes of selection. Warm up

6. Quiz next class over community structures and modes of selections. (10 questions) Write definitions for: taxonomy binomial nomenclature genus family order class phylum kingdom domain biological species phylogeny convergent evolution analogous character cladistics ancestral character derived character cladogram evolutionary systematics phylogenetic tree

7. Population Genetics

8. The Gene Pool • Members of a species can interbreed& producefertile offspring • Species have a shared gene pool • Gene pool – all of the alleles of all individuals in a population

9. The Gene Pool • Different species do NOT exchange genes by interbreeding • Different species that interbreed often produce sterile or less viable offspring e.g. Mule

10. Populations • A group of the same species living in an area • No two individuals are exactly alike (variations) • More Fit individuals survive & pass on their traits

11. Speciation • Formation of new species • One species may split into 2 or more species • A species may evolve into a new species • Requires very long periods of time

12. Modern Evolutionary Thought

13. Modern Synthesis Theory • Combines Darwinian selection and Mendelian inheritance • Population genetics - study of genetic variation within a population • Emphasis on quantitative characters (height, size …)

14. Modern Synthesis Theory • 1940s – comprehensive theory of evolution (Modern Synthesis Theory) • Introduced by Fisher & Wright • Until then, many did not accept that Darwin’s theory of natural selection could drive evolution S. Wright A. Fisher

15. Modern Synthesis Theory • TODAY’S theory on evolution • Recognizes that GENES are responsible for the inheritance of characteristics • Recognizes that POPULATIONS, not individuals, evolve due to natural selection & genetic drift • Recognizes that SPECIATION usually is due to the gradual accumulation of small genetic changes

16. Microevolution • Changes occur in gene pools due to mutation, natural selection, genetic drift, etc. • Gene pool changes cause more VARIATION in individuals in the population • This process is called MICROEVOLUTION • Example: Bacteria becoming unaffected by antibiotics (resistant)

17. Microevolution of Species

18. Causes of Microevolution • Genetic Drift • - the change in the gene pool of a small population due to chance • Natural Selection • - success in reproduction based on heritable traits results in selected alleles being passed to relatively more offspring (Darwinian inheritance) • - Cause ADAPTATION of Populations • Gene Flow • -is genetic exchange due to the migration of fertile individuals or gametes between populations

19. Causes of Microevolution • Mutation • a change in an organism’s DNA • Mutations can be transmitted in gametes to offspring • Non-random mating • - Mates are chosen on the basis of the best traits

20. Genetic Drift

21. Factors that Cause Genetic Drift • Bottleneck Effect • a drastic reduction in population (volcanoes, earthquakes, landslides …) • Reduced genetic variation • Smaller population may not be able to adapt to new selection pressures • Founder Effect • occurs when a new colony is started by a few members of the original population • Reduced genetic variation • May lead to speciation

23. Sources of Variation • Mutations • In stable environments, mutations often result in little or no benefit to an organism, or are often harmful • Mutations are more beneficial (rare) in changing environments  (Example:  HIV resistance to antiviral drugs) • Genetic Recombination • source of most genetic differences between individuals in a population • Co-evolution • -Often occurs between parasite & host and flowers & their pollinators

24. Loss of Genetic Variation • Cheetahs have little genetic variation in their gene pool • This can probably be attributed to a population bottleneck they experienced around 10,000 years ago, barely avoiding extinction at the end of the last ice age

26. Founder’s Effect

27. Bottom-Up and Top-Down Controls: Models based on relationship between adjacent trophic levels • The bottom-up modelof community organization proposes a unidirectional influence from lower to higher trophic levels • In this case, presence or absence of mineral nutrients determines community structure, including abundance of primary producers • The top-down model, also called the trophic cascade model, proposes that control comes from the trophic level above • In this case, predators control herbivores, which in turn control primary producers • Long-term experimental studies have shown that communities vary in their relative degree of bottom-up to top-down control

28. Concept: Disturbance influences species diversity and composition • Decades ago, most ecologists favored the view that communities are in a state of equilibrium • Recent evidence of change has led to a nonequilibrium model, which describes communities as constantly changing after being buffeted by disturbances (such as fire) (a) Soon after fire (b) One year after fire Yellow stone national park- 1988

29. Ecological Succession • Ecological succession is the sequence of community and ecosystem changes (colonized by a variety of species, gradually replaced by other species) after a disturbance: volcanic eruption or a glacier, strip away all the vegetation. • Primary succession occurs where no soil exists (lifeless area) when succession begins. Autotrophic and heterotrophic prokaryotes and protists. Lichens and moss will first colonize the land when soil develops gradually. Then grasses, shrubs, trees will sprout. • Secondary succession begins in an area where soil remains after a disturbance. Recolonization starts with herbaceous species. • Early-arriving species and later-arriving species may be linked in one of three processes: • Early arrivals may facilitate appearance of later species by making the environment favorable • They may inhibit establishment of later species • They may tolerate later species but have no impact on their establishment

31. Glacial retreat and primary succession at Glacier Bay, Alaska 1941 1907 2 Pioneer stage, with Pioneer stage-fireweed, liverworts, mosses 1 Dryas stage 0 5 10 15 Kilometers 1860 Glacier Bay Alaska 1760 4 3 Spruce stage Alder stage

32. 60 Successional stage • Retreating glaciers provide a valuable field-research opportunity for observing succession • Succession on the moraines in Glacier Bay, Alaska, follows a predictable pattern of change in vegetation and soil characteristics • Succession is the result of changes induced by the vegetation itself • On the glacial moraines,vegetation lowers thesoil pH(8.4-7-4.0) and • increases soil nitrogen • content. 50 40 Soil nitrogen (g/m2) 30 20 10 0 Pioneer Dryas Alder Spruce

33. Human Disturbance • Humans have the greatest impact on biological communities worldwide • Human disturbance to communities usually reduces species diversity • Humans also prevent some naturally occurring disturbances, which can be important to community structure • Logging and clearing for urban development, mining, farming, deep sea trawlers.

34. Concept: Community ecology is useful for understanding pathogen life cycles and controlling human disease • Ecological communities are universally affected by pathogens, which include disease-causing microorganisms and viruses. • Pathogens can alter community structure quickly & extensively (coral reef communities are being decimated by white-band disease - destroys habitats) • Human activities are trans-porting pathogens around theworld at unprecedented rates • Community ecology is neededto help study and combatthem

36. Guided Practice 1. Most organisms are either a predator or a prey, however not all of them have the adaptation of camouflage. What types of organisms do you think would not need camouflage as an adaptation? Explain your answer 2. In the graph below, which line represents the prey and which line represents the predator? How can you tell?

37. Modes of Natural Selection

38. Modes of Natural Selection • Directional Selection • Favors individuals at one end of the phenotypic range • Most common during times of environmental change or when moving to new habitats • Disruptive selection • Favors extreme over intermediate phenotypes • Occurs when environmental change favors an extreme phenotype

39. DirectionalSelection

40. Disruptive Selection

41. Modes of Natural Selection • Stabilizing Selection • Favors intermediate over extreme phenotypes • Reduces variation and maintains the cureent average • Example: Human birth weight

43. Variations in Populations

44. Geographic Variations • Variation in a species due to climate or another geographical condition • Populations live in different locations • Example: Finches of Galapagos Islands & South America

46. Heterozygote Advantage • Favors heterozygotes (Aa) • Maintains both alleles (A,a) instead of removing less successful alleles from a population • Sickle cell anemia • > Homozygotes exhibit severe anemia, have abnormal blood cell shape, and usually die before reproductive age. • > Heterozygotes are less susceptible to malaria

47. Sickle Cell and Malaria

49. Other Sources of Variation • Mutations • In stable environments, mutations often result in little or no benefit to an organism, or are often harmful • Mutations are more beneficial (rare) in changing environments  (Example:  HIV resistance to antiviral drugs) • Genetic Recombination • source of most genetic differences between individuals in a population • Co-evolution • -Often occurs between parasite & host and flowers & their pollinators

50. Coevolution