Biodiversity:

1. Evolution and Community Interactions Biodiversity:

2. Overview What is biodiversity? How did Earth get such a variety of life? What role does species interaction play? What are the benefits of biodiversity? How have humans impacted biodiversity? What is being done to maintain biodiversity?

3. Essential Questions Be able to describe how the earth is “just right” for life What is evolution? How has evolution lead to the current diversity of organisms? What is an ecological niche? How does it relate to adaptation to changing environmental conditions? How do extinction of species and formation of new species affect biodiversity?

4. Evolution: The Origin of Biodiversity What evolution is Descent with Modification A regular progression in the complexity of life forms on Earth Chemical vs Biological Chemical: How did the first life forms originate? Many theories, Little consensus Biological: How has life changed over time? Darwin and Natural Selection: Accepted by most scientists Evidence Fossils (Video clip) Anatomy Molecular

5. Earth: The Just Right Planet Temperature Distance from Sun Geothermal energy from core Temperature fluctuated only 10-20oC over 3.7 billion years despite 30-40% increase in solar output Waterexists in 3 phases Right size (=gravitational mass to keep atmosphere) Resilient and adaptive Each species here today represents a long chain of evolution and each plays a role in its respective ecosystem

6. Summary of Evolution of Life Chemical Evolution (1 billion years) Formation of the earth’s early crust and atmosphere Small organic molecules form in the seas Large organic molecules (biopolymers) form in the seas First protocells form in the seas Biological Evolution (3.7 billion years) Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas Variety of multicellular organisms form, first in the seas and later on land

7. Origins of Life on Earth4.7-4.8 Billion Year History Evidence from chemical analysis and measurements of radioactive elements in primitive rocks and fossils. Life developed over two main phases: Chemical evolution (took about 1 billion years) Organic molecules, proteins, polymers, and chemical reactions to form first “protocells” Biological evolution (3.7 billion years) From single celled prokaryotic bacteria to eukaryotic creatures to eukaryotic multicellular organisms (diversification of species)

8. KWL Musical Showoff Write down what you Know and Want to know about the following: Definition and relationship among: Evolution Natural Selection Adaptation Biodiversity = Speciation – Extinction Musical Circles Discuss what you Learned

9. Biological Evolution Modern humans (Homo sapiens) appear about 2 seconds before midnight Age of mammals Recorded human history begins 1/4 second before midnight Age of reptiles Insects and amphibians invade the land Origin of life (3.6–3.8 billion years ago) Plants invade the land Fossils become abundant Fossils present but rare Evolution and expansion of life

10. Fossil Record Most of what we know of the history of life on earth comes from fossils (SJ Gould) Give us physical evidence of organisms Show us internal structure Uneven and incomplete record of species We have fossils for 1% of species believed to have lived on earth Some organisms left no fossils, others decomposed, others have yet to be found. Other info from ancient rocks, ice core, DNA The whale as an exampleOther evidence here

11. Evidence of Environmental Effect:Convergent Evolution • Analogy • Similarity in body parts in different organisms • Attributable to similar environmental pressures

12. Evidence of Common Ancestry:Divergent Evolution • Homology • Similarity in body parts in different organisms • Attributable to descent from a common ancestor

13. Natural Selection Genetic Variation Variations are heritable Overproduction of Offspring Malthus Struggle for Existence Competition, Predation, etc… Differential Survival and Reproduction Fitness = # of offspring left to next generation

14. Darwinian Natural Selection Three conditions necessary for evolution by natural selection to occur: Natural variability for a trait in a population Trait must be heritable (has a genetic basis so that it can be passed onto offspring) Trait must lead to differential reproduction Must allow some members of the population to leave more offspring than other members of the population w/o trait) Grant’s Finches A heritable trait that enables organisms to survive and reproduce is called an adaptation (Lamark is wrong…)

15. Tutorial

16. What is Adaptation? Noun Result of Natural Selection Favorable trait that has accumulated in a species through years of natural selection Verb The process of accumulating favorable traits Occurs OVER TIME to the POPULATION AS A WHOLE (i.e., Individuals do not adapt, populations do)

17. Take Home #1 When faced with a change in environmental condition, a population of a species can: Adapt via natural selection Migrate (if possible) to an area with more favorable conditions (Mars & Atlantis?) Become extinct Natural selection can only act on inherited alleles already present in the population—do not think that the environment creates favorable heritable characteristics!

18. Steps of Evolution Genetic variation is added to genotype by mutation Mutations lead to changes in the phenotype Phenotype is acted upon by nat’l selection Individuals more suited to environment produce more offspring (contribute more to total gene pool of population) Population’s gene pool changes over time Speciation may occur if geographic and reproductive isolating mechanisms exist… Natural Selection in action ... A demonstration...

19. Predator Prey Cycles:Who Controls Whom? Historical Data The Lotka-Volterra Equations

20. Coevolution Interactions between species can cause microevolution Changes in the gene pool of one species can cause changes in the gene pool of the other Adaptation follows adaptation in something of a long term “arms race” between interacting populations of different populations The Red Queen Effect Can also be symbiotic coevolution Angiosperms and insects (pollinators) Corals and zooxanthellae Rhizobium bacteria and legume root nodules

21. Co-Evolution: Species affecting each other • The Red Queen Effect • "Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!" • Evolution is a continuous, never ending, ever changing process

22. Monarchs, Milkweed and Viceroys • Many Insects eat milkweed • Milkweed evolves a sticky latex that deters herbivory • Monarchs evolve an enzyme that thins the latex • Monarchs have a food source without competitors • The latex makes Monarchs distasteful to their predators • Viceroys look like Monarchs but taste fine • Batesian Mimicry = False Advertising

23. Orchids and Wasps Flowers using insects

24. Evolution The change in a POPULATION’S genetic makeup (gene pool) over time (successive generations) Those with the best phenotype and genotype survive to reproduce and pass on traits All species descended from earlier ancestor species Microevolution Small genetic changes in a population such as the spread of a mutation or the change in the frequency of a single allele due to selection (changes to gene pool) Not possible without genetic variability in a pop… Macroevolution Long term large scale evolutionary changes through which new species are formed and others are lost through extinction

25. Microevolution Changes in a population’s gene pool over time. Genetic variability within a population is the catalyst Four Processes cause Microevolution Mutation (random changes in DNA—ultimate source of new alleles) [stop little] Exposure to mutagens or random mistakes in copying Random/unpredictable relatively rare Natural Selection (best produce most offspring) Gene flow (movement of genes between pop’s) Genetic drift (change in gene pool due to random/chance events) Peppered moth of England; El Nino Galapagos

26. Gene Flow and Genetic Drift Gene Flow Flow of alleles Emigration and immigration of individuals Genetic Drift Random change in allele frequencies over generations brought about by chance In the absence of other forces, drift leads to loss of genetic diversity

27. Genetic Drift Magnitude of drift is greatest in small populations

28. Three types of Natural Selection Directional Allele frequencies shift to favor individuals at one extreme of the normal range Only one side of the distribution reproduce Population looks different over time Peppered moths and genetic resistance to pesticides among insects and antibiotics in bacteria Stabilizing Favors individuals with an average genetic makeup Only the middle reproduce Population looks more similar over time (eliminates extremes) Diversifying (Disruptive) Environmental conditions favor individuals at both ends of the genetic spectrum Population split into two groups

29. Directional Change in the Range of Variation • Directional Selection • Shift in allele frequency in a consistent direction • Phenotypic Variation in a population of butterflies

30. The Case of the Peppered Moths Industrial revolution Pollution darkened tree trunks Camouflage of moths increases survival from predators Directional selection caused a shift away from light-gray towards dark-gray moths

31. Directional Selection Pesticide Resistance Pest resurgence Antibiotic Resistance Grant’s Finch Beak Data With directional selection, allele frequencies tend to shift in response to directional changes in the environment

32. Selection Against or in Favor of Extreme Phenotypes • Stabilizing Selection • Intermediate forms of a trait are favored • Alleles that specify extreme forms are eliminated from a population • Clutch size in birds • Shell size in turtles

33. 20 100 70 50 30 15 20 percent of population percent of mortality 10 10 5 5 3 2 1 2 3 4 5 6 7 8 9 10 11 birth weight (pounds) An Example of Stabilizing Selection

34. Selection Against or in Favor of Extreme Phenotypes • Disruptive Selection • Both forms at extreme ends are favored • Intermediate forms are eliminated • Bill size in African finches

35. 60 50 Number of individuals 40 30 20 10 10 1.12 15.7 18.5 Widest part of lower bill (millimeters) Fig. 18.9, p. 289

36. Special Types of Selection • Balancing selection • Balanced polymorphism • Sickle-Cell Anemia • Malaria Distribution of Malaria Sickle Cell Trait

37. What is a Species? Morphological Species Concept Based on appearance alone Biological Species Concept A species is one or more populations of individuals that are interbreeding under natural conditions and producing fertile offspring, and are reproductively isolated from other such populations

38. Key Concepts: A species consist of one or more populations of individuals that can interbreed and produce offspring Populations of a species have a shared genetic history Speciation is the process by which daughter species evolve from a parent species

39. Key Concepts: Geographic barriers can start the process of speciation Allopatric speciation A species can form within the range of a parent species Sympatric speciation

40. Speciation Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Northern population Arctic Fox Spreads northward and southward and separates Different environmental conditions lead to different selective pressures and evolution into two different species. Early fox population Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Southern population Gray Fox

41. Speciation Two species arise from one: As a population of organisms exploits new niches they become reproductively isolated from the parent population leading to adaptive radiation Requires Reproductive isolation: Any heritable feature of body, form, functioning, or behavior that prevents breeding between one or more genetically divergent populations Geographic: Physically separated Temporal: Mate at different times Behavioral: Bird calls / mating rituals Anatomical: Picture a mouse and an elephant hooking up Genetic Inviability: Mules Allopatric Speciation that occurs when 2 or more populations of a species are geographically isolated from one another The allele frequencies in these populations change Members become so different that that can no no longer interbreed See animation Sympatric Populations evolve with overlapping ranges Behavioral barrier or hybridization or polyploidy

42. The Case of the Road-Killed Snails Study of neighboring populations of snails Genetic variation is greater between populations living on opposite sides of the street Color - 3 alleles of a gene

43. Allopatric Speciation • Physical barrier prevents gene flow between populations of a species • Archipelago hotbed of speciation

44. Island Biogeography

45. Adaptive Radiation • Evolution of new species from a common ancestral stock • Taking advantage of opportunity • Result of selective pressure reducing competition

46. Pre-Zygotic Isolation Mating or zygote formation is blocked Temporal Isolation Behavioral Isolation Mechanical Isolation Ecological Isolation Gamete Mortality

47. Temporal Isolation in Apple Maggots

48. Fig. 18.10, p. 290

49. Post-Zygotic Isolation Hybrids don’t work Zygotic mortality - Egg is fertilized but zygote or embryo dies Hybrid inviability - First generation hybrid forms but shows low fitness Hybrid infertility - Hybrid is fully or partially sterile

50. Extinctions - End of The Line Background extinction Local changing conditions Role of Humans? Mass extinction Catastrophic global event Temperature changes Asteroids Mass extinctions Reduce competition Open niches to exploitation by new species Leads to adaptive radiation