1. Biodiversity and Evolution Chapter 4

2. Core Case Study: Why Should We Care about the American Alligator?  Largest reptile in North America:  1930s: Hunters and poachers  Importance of gator holes and nesting mounds  1967: endangered species  1977: comeback, threatened species KEYSTONE SPECIES-- has a large effect on other species in the ecosystem

3. 4-1 What Is Biodiversity and Why Is It Important?  Concept 4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth.  Species diversity: variety of species Genetic diversity  Ecosystem diversity: variety of ecosystems Each contains huge genetic and species diversity  Functional diversity: variety of processes (nutrient cycling, energy flow)

4. Natural Capital: Major Components of the Earth’s Biodiversity

5. 4-2 Where Do Species Come From?  Concept 4-2A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations.  Concept 4-2B Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

6. Biological Evolution by Natural Selection Explains How Life Changes over Time  Biological evolution: process where life changes over time through changes in the genes of the populations  Natural selection-mechanism for evolution Charles Darwin-1859 On the Origin of the Species Major ideas Organisms produce more offspring than can survive Competition arises for resources Individuals with a characteristic that aids survival are more likely to survive Must lead to Differential Reproduction  “Survival of the Fittest” --fittest means best suited for a particular environment; not necessarily strongest

7. The Fossil Record Tells Much of the Story of Evolution  Fossils Physical evidence of ancient organisms Reveal what their internal structures looked like  Fossil record is incomplete: why?

8. The Genetic Makeup of a Population Can Change  Populations evolve by becoming genetically different  Genetic variations First step in biological evolution Occurs through mutations in reproductive cells-- change in DNA nitrogen base code  Adaptation (Adaptive Trait): heritable trait that enables an individual organism to survive through natural selection and to reproduce more than other individuals in the environment

9. Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring  When environmental conditions change, populations Adapt Migrate Become extinct

10. Evolution by Natural Selection: Genetic Resistance

11. Case Study: How Did Humans Become Such a Powerful Species?  Three human adaptations Strong opposable thumbs--allow us to grip objects Walk upright--can use arms better, do things while walking Complex brain--problem solving ability Will our complex brain help us solve the environmental problems we are creating?

12. Three Common Myths about Evolution through Natural Selection  “Survival of the fittest” is not “survival of the strongest”  Organisms do not develop traits out of need or want  No grand plan of nature for perfect adaptation

13. Animation: Change in moth population An example of Natural Selection

14. 4-3 How Do Geological Processes and Climate Change Affect Evolution?  Concept 4-3 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.  Tectonic plates affect evolution and the location of life on earth Location of continents and oceans Species physically move, or adapt, or form new species through natural selection  Earthquakes  Volcanic eruptions

15. Movement of the Earth’s Continents over Millions of Years

16. Climate Change and Catastrophes Affect Natural Selection  Ice ages followed by warming temperatures  Collisions between the earth and large asteroids New species appear Extinction of other species The 4 scientific principles of sustainability-- especially biodiversity-- have enabled life of earth to adapt to drastic changes in environmental conditions

17. Changes in Ice Coverage in the Northern Hemisphere During the last 18,000 Years

18. Science Focus: Earth Is Just Right for Life to Thrive  Certain temperature range -always 10-20ºC (50- 68ºF) average surface temperature  Dependence on water --water vapor can condense and form rain  Rotation on its axis --keeps all sides of Earth at correct temperature for water-based life  Revolution around the sun - correct distance from sun to allow water vapor to condense  Enough gravitational mass -keeps Fe and N in core molten and keeps atmosphere in place

19. 4-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity?  Concept 4-4A As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity.  Concept 4-4B Human activities can decrease biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.

20. How Do New Species Evolve?  SPECIATION: formation of 2 species from one species  Most common mechanism Geographic speciation: different groups of same population become physically Isolated from one another this leads to: Reproductive isolation: long-term geographic separation of members of a particular sexually reproducing species leads to the isolated populations becoming so different that they can’t reproduce

21. Geographic Isolation Can Lead to Reproductive Isolation

22. Extinction is Forever  Extinction: entire species ceases to exist  Endemic species-species found only in 1 area Particularly vulnerable Ex. Found on islands or tropical rain forests  Background extinction-species slowly become extinct as environmental conditions change over time-- constantly occuring  Mass extinction Catastrophic event with large number of species wiped out at once How numbered is debated: 3–5

23. Animation: Speciation on an archipelago

24. 4-5 What Is Species Diversity and Why Is It Important?  Concept 4-5 Species diversity is a major component of biodiversity and tends to increase the sustainability of ecosystems.  Species diversity: 2 components 1. Species richness-number of different species 2. Species evenness-relative abundance of individuals within each species  SPECIATION-EXTINCTION = BIODIVERSITY  Diversity varies with geographical location Most species-rich communities Tropical rain forests- Coral reefs Ocean bottom zone Large tropical lakes

25. Variations in Species Richness and Species Evenness Coral Reef: High Richness; Low Evenness Canadian Aspen Trees: Low Richness, High Evenness

26. Species Diversity  Shannon; Shannon-Wiener; Shannon-Weaver Index: Measures the amount of diversity in a habitat at a given time. Can be used in comparisons. 0 value = little diversity; 4 = high diversity H = Shannon’s diversity index S = Richness (number of species in community) P i = proportion of S made up of species “i” E = Evenness (equitability) the amount of diversity in a habitat at a given time. Can be used in comparisons. 0 value = little diversity; 4 = high diversity H = Shannon’s diversity index S = Richness (number of species in community) P i = proportion of S made up of species “i” E = Evenness (equitability) Don’t let the formula scare you:

27. Science Focus: Species Richness on Islands  Species equilibrium model, theory of island biogeography Rate of new species immigrating should balance with the rate of species extinction  Island size and distance from the mainland need to be considered

28. 4-6 What Roles Do Species Play in Ecosystems?  Concept 4-6A Each species plays a specific ecological role called its niche.  Concept 4-6B Any given species may play one or more of five important roles—native, nonnative, indicator, keystone, or foundation roles—in a particular ecosystem.

29. Each Species Plays a Unique Role in Its Ecosystem  Ecological niche, niche Pattern of living  Generalist species Broad niche Ex. Cockroach-live everywhere; high reproductive rate  Specialist species Narrow niche Ex. Tiger Salamander, Giant Panda

30. Specialized Feeding Niches of Various Bird Species in a Coastal Wetland

31. Niches Can Be Occupied by Native and Nonnative Species  Native species  Nonnative species; invasive, alien, or exotic species May spread rapidly Not all are villains

32. Indicator Species Serve as Biological Smoke Alarms  Indicator species Can monitor environmental quality Trout Birds Butterflies Frog  Case Study: Amphibians are Vanishing (p. 93)  Habitat loss and fragmentation Nonnative predators and competitors  Prolonged drought Overhunting  PollutionClimate change  Increase in UV radiationViral and fungal diseases  Parasites Importance of amphibians

33. Case Study: Why Are Amphibians Vanishing?  Importance of amphibians Sensitive biological indicators of environmental changes Adult amphibians Important ecological roles in biological communities Genetic storehouse of pharmaceutical products waiting to be discovered

34. Keystone, Foundation Species Determine Structure, Function of Their Ecosystems  Keystone species: Play a larger role in ecosystem than is expected from one species Pollinators Top predator Ex. Alligator, wolf, sea star  Foundation species: Create or enhance their habitats, which benefit others Elephants Beavers

35. Case Study: Why Should We Protect Sharks?  Keystone species Eat dead and dying fish in the ocean Strong immune systems Wounds do not get infected Almost never get cancer Could help humans if we understood their immune system