Biodiversity and Evolution

1. Biodiversity and Evolution Chapter 4 (Miller and Spoolman, 2010)

2. Core Case Study: Why Should We Care about the American Alligator? • Largest reptile in North America and plays a number of roles in the ecosystem. • Role is ecosystem is called a niche. • Gator holes • Nesting mounds • Predator • Keeps areas of open water free of invading vegetation • 1930s: Hunters and poachers • 1967: endangered species • 1977: comeback, reclassified as threatened species • Highlights how interactions between species affect the structure and function of ecosystems.

3. Figure 4-1 The American alligator plays an important role in its marsh and swamp habitats in the southeastern U.S. Since being classified as endangered in 1967, it has recovered enough to have its status changed from endangered to threatened—an outstanding success story in wildlife conservation.

4. 4-1 What Is Biodiversity and Why Is It Important?

5. 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.

6. Biodiversity Is a Crucial Part of the Earth’s Natural Capital (1) • Biological diversity, or biodiversity – the variety of the earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life. • Biodiversity is vital renewable resource important to sustainability. • Natural capital and natural services • Food, wood, fibers, energy, and medicines—hundreds of billions in natural services. • Preserved air and water quality and maintains fertility of soils. • Helps to dispose of wastes and control pest populations.

7. Biodiversity Is a Crucial Part of the Earth’s Natural Capital (2) • Species diversity • Genetic diversity • Ecosystem diversity • The variety of ecosystems are the storehouses of genetic and species diversity. • Functional diversity • The variety of processes such as matter cycling and energy flow in ecosystems as species interact with one another in food webs.

9. 4-2 Where Do Species Come From?

10. 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).

11. Biological Evolution by Natural Selection Explains How Life Changes over Time (1) • Biological evolution – process whereby earth’s life changes over time through changes in the genes of populations. • That life on earth had gone though changes had been around since the time of the ancient Greeks. • Not until 1858 when a mechanism was proposed independently by • Charles Darwin (1809-1882) • On the Origin of Species by Means of Natural Selection (1859) • Alfred Russel Wallace (1823-1913)

12. Biological Evolution by Natural Selection Explains How Life Changes over Time (2) • Natural selection – occurs when some individuals of a population have genetically based traits that enhance their ability to survive and produce offspring with the same traits. • A change in the genetic characteristics of a population from one generation to another is known as biological evolution, or simply evolution. • Life has evolved into six major groups of organisms—kingdoms . • Result is viewed as an ever branching tree of species diversity called the tree of life.

13. Figure 4.3Overview of the evolution of life on the earth into six major kingdoms of species as a result of natural selection.

14. Human Family Tree(From http://humanorigins.si.edu/evidence/human-fossils/species/human-family-tree

15. The Fossil Record Tells Much of the Story of Evolution • Fossils – mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks. • Physical evidence of ancient organisms • Reveal what their internal structures looked like • Fossil record is the world’s cumulative body of fossils. • Incomplete, why?

16. Figure 4.4Fossilized skeleton of a herbivore that lived during the Cenozoic era from 26-66 million years ago.

17. The Genetic Makeup of a Population Can Change • Populations—not individuals—evolve by becoming genetically different. • Genetic variability • First step in biological evolution • Occurs through mutations—random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring, i.e. in reproductive cells. • Most mutations are caused by random errors while DNA is copying, but others are cause by mutagens.

18. Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring (1) • Second step in biological evolution is natural selection which acts on individuals. • Natural selection occurs when some individuals of a population have genetically based traits (resulting from mutations) that enhance their ability to survive and produce offspring with these traits. • Adaptation – a heritable trait that enables a individual organism to survive through natural selection and reproduce more than other individuals under the prevailing environmental conditions. • Leads to differential reproduction • Examples: • Fur color and thickness in mammals and • Genetic resistance in bacteria

20. Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring (2) • Summary • Genes mutate, individuals are selected, and populations evolve that are better adapted to survive and reproduce under existing environmental conditions. • When environmental conditions change, populations • Adapt • Migrate • Become extinct

21. Figure 4.5Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria.

22. Case Study: How Did Humans Become Such a Powerful Species? • Like many species, humans have survived and thrived because we have certain traits that allow us to adapt to and modify parts of the environment to increase our survival chances. • Three human adaptations • Strong opposable thumbs • Walk upright • Complex brain

23. Adaptation through Natural Selection Has Limits • Would adaptations evolve by natural selection to cope with increasing UV light levels (skin), air pollutants (lungs), and other toxins (liver)? • The answer is no for two reasons: • Genetic change must precede change in the environmental conditions. • Reproductive capacity • Humans and other long-lived species do not reproduce rapidly. Thus, significant changes in populations genetic make-up takes long period of time (thousands to millions of years).

24. Three Common Myths about Evolution through Natural Selection • Myth 1: “Survival of the fittest” means “survival of the strongest” • Fitness is a measure of reproductive success, not strength. • Myth 2: Organisms develop traits out of need or want. • Myth 3: There is a grand plan of nature for perfect adaptation. • Evolutionary process by all accounts, appears to be a random, branching process that results in a great variety of species.

25. 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.

26. Geologic Processes Affect Natural Selection • Tectonic plates affect evolution and the location of life on earth. • Location of continents and oceans influence climate influences where plants and animals can live. • Allows species physically move, adapt to new environments, and form new species through natural selection • Earthquakes • Fissure can separate and isolate populations. • Volcanic eruptions • Destroys habitat, and reduces or wipes out populations.

27. Figure 4.6Over millions of years, the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species, as land areas split apart, and also in the rise of new species when isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago, all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right

28. Climate Change and Catastrophes Affect Natural Selection • Glacial and interglacial periods: Ice ages followed by warming temperatures. • Ice sheets and sea levels. • Long-term climate changes have a major effect on biological evolution by determining where different types of organisms can survive and by changing the locations of ecosystems such as deserts, grasslands and forests. • Collisions between the earth and large asteroids. • New species • Extinction

29. Figure 4.7Changes in ice coverage in the northern hemisphere during the past 18,000 years. Question: What are two characteristics of an animal and two characteristics of a plant that natural selection would have favored as these ice sheets (left) advanced? (Data from the National Oceanic and Atmospheric Administration)

30. Science Focus: Earth Is Just Right for Life to Thrive Life can thrive only within a certain temperature range. Dependence on water Average distance of orbit Rotation on its axis and revolution around the sun Enough gravitational mass Oxygen and CO2 levels.

31. 4-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity?

32. 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.

33. How Do New Species Evolve? • Speciation – process by which natural selection causes the formation of two new species from one. • Mechanisms of Speciation • Geographic isolation • Reproductive isolation • Humans are playing an increasing role in the process of speciation. • Selective breeding/artificial selection • Genetic engineering

34. Figure 4.8Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation.

35. Extinction is Forever • Extinction • Endemic species • Particularly vulnerable

36. Figure 4.9Male golden toad in Costa Rica’s high-altitude Monteverde Cloud Forest Reserve. This species has recently become extinct, primarily because changes in climate dried up its habitat.

37. Extinction Can Affect One Species or Many Species at a Time (1) • All species eventually become extinct. • Background extinction rate - low rate at which species have become extinct. • Annually: 1-5 species per million species. • Drastic changes in environmental conditions. • Mass extinction rate – catastrophic, widespread extinction of large groups of species. • Perhaps 25–70 % are wiped out in a geological periods lasting up to 5 years.

38. Extinction Can Affect One Species or Many Species at a Time (2) • There have been five mass extinctions. • Most recent was 65 mya. • 250 mya, 95 % of species disappeared. • A mass extinction provides an opportunity for the evolution of new species that can fill vacant ecological niches, or newly created ones • Humans have become a major force in the premature extinction of a growing list of species.

39. Science Focus: We Have Two Ways to Change the Genetic Traits of Populations Figure 4-A An example of genetic engineering. The 6-month-old mouse on the left is normal; the same-age mouse on the right has a human growth hormone gene inserted in its cells. Question: How do you think the creation of such species might change the process of evolution by natural selection. • Artificial selection • Genetic engineering, gene splicing • Consider • Ethics • Morals • Privacy issues • Harmful effects

40. 4-5 What Is Species Diversity and Why Is It Important?

41. 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.

42. Species Diversity: Variety and Abundance of Species in a Particular Place • Species diversity • Species richness – number of species • Species evenness – relative abundance • Diversity varies with geographical location. • In terrestrial ecosystems, highest in the tropics and declines as we move from equator toward poles. • Most species-rich communities • Tropical rain forests • Coral reefs • Ocean bottom zone • Large tropical lakes

43. Figure 4.10Variations in species richness and species evenness. A coral reef (left), with a large number of different species (high species richness), generally has only a few members of each species (low species evenness). In contrast, a grove of aspen trees in Alberta, Canada, in the fall (right) has a small number of different species (low species richness), but large numbers of individuals of each species (high species evenness).

44. Science Focus: Species Richness on Islands • Species equilibrium model, or theory of island biogeography • Species richness of an island reaches and equilibrium and depends on: • Rate of new species immigrating • Rate of species extinction • Two features of an island affect immigration and extinction rates. • Island size • Distance from the mainland • Theory is applied to habitat fragments and can be used to make management decisions.

45. Species-Rich Ecosystems Tend to Be Productive and Sustainable • How does species richness affect ecosystems? • Is productivity higher in species-rich ecosystems? • Does species richness enhance stability, or sustainability. • Most studies seem to support that species richness seems to increase productivity and stability or sustainability • More research is needed before these observations become accepted as theory. • One question new question: Just how much species richness is needed? • Evidence suggest that anything greater than between 10-40 producer species does not necessarily increase productivity.

46. 4-6 What Roles Do Species Play in Ecosystems?

47. 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.

48. Each Species Plays a Unique Role in Its Ecosystem • Ecological niche, or simply niche • Pattern of living, a roles in an ecosystem • Includes everything that affects a species’ survival • Generalist species • Broad niche • Can live in many different places, eat many things tolerate a wide range of environmental conditions. • Examples: Flies, rats, mice, rats, white-tailed deer, raccoons, and humans • Specialist species • Narrow niche • Can live in only certain habitats, use only few types of food, and tolerate a narrow range of environmental factors. • Example: Tiger salamander, giant panda • Better to be a generalist or a specialist?

49. Figure 4.11Specialist species such as the giant panda have a narrow niche (left) and generalist species such as a raccoon have a broad niche (right).

50. Figure 4.13Specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources.