Biodiversity, Species Interactions, and Population Control

1. Biodiversity, Species Interactions, and Population Control Chapter 5

2. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? • Hunted nearly to extinction in native California coast habitat • Partial recovery • Why care about sea otters? • Ethics • Keystone species in kelp forests • Tourism dollars

3. Science Focus: Why Should We Care about Kelp Forests? • Kelp forests: biologically diverse marine habitat • Renewable resource: harvested for algin, a thickening agent used in toothpaste, cosmetics, ice cream, etc. • Major threats to kelp forests • Sea urchins (main food source for dwindling sea otter populations) • Pollution from water run-off • Global warming

4. Southern Sea Otter

5. Purple Sea Urchin

6. Science Focus: Why Are Protected Sea Otters Making a Slow Comeback? • Otters are k-selected and face several limiting factors: • Low biotic potential • Prey for orcas • Cat parasites • Thorny-headed worms • Toxic algae blooms • PCBs and other toxins • Oil spills

7. Population Size of Southern Sea Otters Off the Coast of So. California (U.S.)

8. 5-1 How Do Species Interact? • Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.

9. Species Interact in Five Major Ways • Interspecific Competition • Predation • Parasitism • Mutualism • Commensalism • Interactions helps limit population growth (principle of sustainability)

10. Most Species Compete with One Another for Certain Resources • Competition • Greater niche overlap=greater competition • Niche overlap- two species complete with one another for the same resource • Competitive exclusion principle- no two species can occupy the same niche for very long, especially in the same ecosystem

11. Most Consumer Species Feed on Live Organisms of Other Species (1) • Predators may capture prey by • Walking • Swimming • Flying • Pursuit and ambush • Camouflage • Chemical warfare **predators stalk and kill there prey! Different from parasites!**

12. Most Consumer Species Feed on Live Organisms of Other Species (2) • Prey may avoid capture by • Camouflage • Chemical warfare • Warning coloration • Mimicry • Deceptive looks • Deceptive behavior

13. Most Consumer Species Feed on Live Organisms of Other Species (3) • Edward O. Wilson • If it is small and strikingly beautiful, it is probably poisonous • If it is strikingly beautiful and easy to catch, it is probably deadly • Prey Adaptations • Warning coloration • Mimicry

14. (a) Span worm (b) Wandering leaf insect (c) Bombardier beetle (d) Foul-tasting monarch butterfly (f) Viceroy butterfly mimics monarch butterfly (e) Poison dart frog (g) Hind wings of Io moth resemble eyes of a much larger animal. (h) When touched, snake caterpillar changes shape to look like head of snake. Stepped Art Fig. 5-2, p. 103

15. Predator and Prey Species Can Drive Each Other’s Evolution • Intense natural selection pressures between predator and prey populations • Prey organisms will experience natural selection in their traits that keep them from getting eaten • Predator organisms will experience natural selection in traits that make them better hunters/stalkers • Co-evolution- changes in the gene code of one species lead to changes in another species • Constant race

16. Coevolution: A Langohrfledermaus Bat Hunting a Moth

17. Some Species Feed off Other Species by Living on or in Them • Parasitism • Increases Species Richness • Keeps host populations in check • Parasite-host interaction may lead to co-evolution • Ex: malaria parasites have developed a defense against being swept into the spleen (thousands of different version of a sticky protein)

18. Parasitism: Tree with Parasitic Mistletoe, Trout with Blood-Sucking Sea Lampreys

19. In Some Interactions, Both Species Benefit • Mutualism • Nutrition and protection relationship • Gut inhabitant mutualism

20. Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish

21. In Some Interactions, One Species Benefits and the Other Is Not Harmed • Commensalism • Epiphytes or “air plants” attach to tree trunks or branches (solid surface, more sunlight), without leaching nutrients from the tree • Birds nesting in trees

22. Commensalism: Bromiliad Roots on Tree Trunk Without Harming Tree

23. 5-2 How Can Natural Selection Reduce Competition between Species? • Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.

24. Some Species Evolve Ways to Share Resources • Resource partitioning- species competing for the same resource find a way to share it • Reduce niche overlap • Use shared resources at different • Times • Places • Ways

25. Competing Species Can Evolve to Reduce Niche Overlap

26. Sharing the Wealth: Resource Partitioning

27. Specialist Species of Honeycreepers

28. 5-3 What Limits the Growth of Populations? • Concept 5-3 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

29. Populations Have Certain Characteristics (1) • Populations differ in • Distribution • Numbers • Age structure • Population dynamics-study of how these factors change in response to environmental conditions

30. Populations Have Certain Characteristics (2) • Changes in population characteristics due to: • Temperature • Presence of disease organisms or harmful chemicals • Resource availability • Arrival or disappearance of competing species

31. Most Populations Live Together in Clumps or Patches (1) • Population distribution • Clumping • Uniform dispersion • Random dispersion • Why clumping? • Species tend to cluster where resources are available • Groups have a better chance of finding clumped resources • Protects some animals from predators • Packs allow some to get prey • Temporary groups for mating and caring for young

32. Populations Can Grow, Shrink, or Remain Stable (1) • Population size governed by • Births • Deaths • Immigration • Emigration • Population change = (births + immigration) – (deaths + emigration)

33. Populations Can Grow, Shrink, or Remain Stable (2) • Age structure • Pre-reproductive age • Reproductive age • Post-reproductive age • Should be able to predict population changes for the future based on age structure • ***review age structure shape of rapid growth, slow, growth, stable population, from biology (also in Chapter 6)

34. No Population Can Grow Indefinitely: J-Curves and S-Curves (1) • Biotic potential- capacity for growth • Low (large animals) • High (tiny organism—microbes) • Intrinsic rate of increase (r)- The rate at which a pop would grow with unlimited resources • Individuals in populations with high r • Reproduce early in life • Have short generation times • Can reproduce many times • Have many offspring each time they reproduce

35. No Population Can Grow Indefinitely: J-Curves and S-Curves (2) • Size of populations limited by • Light • Water • Space • Nutrients • Exposure to too many competitors, predators or infectious diseases

36. No Population Can Grow Indefinitely: J-Curves and S-Curves (3) • Environmental resistance- combinations of all factors that limit population growth • Carrying capacity (K)- maximum population of a species a habitat can sustain • Biotic potential + Environmental Resistance • Exponential growth (J) • Logistic growth (S)

37. No Population Can Continue to Increase in Size Indefinitely

38. Logistic Growth of a Sheep Population on the island of Tasmania, 1800–1925

39. When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash • Carrying capacity is not static—changes as resource availability changes! • Reproductive time lag may lead to overshoot • Dieback (crash) • Births decrease • Deaths increase • Damage may reduce area’s carrying capacity

40. Exponential Growth, Overshoot, and Population Crash of a Reindeer

41. Species Have Different Reproductive Patterns • r-Selected species, opportunists • Reproduce early in life, small org., large numbers, no parenting , short life spans • K-selected species, competitors • Reproduce later in life, large org., small numbers, parenting, long life spans

42. Carrying capacity K K species; experience K selection Number of individuals r species; experience r selection Time Fig. 5-14, p. 112

43. Genetic Diversity Can Affect the Size of Small Populations • Founder effect- individuals of a population colonize new area • Demographic bottleneck- few individuals survive a catastrophe • Genetic drift- random changes in genes that can lead to unequal reproductive success • Inbreeding- individuals of a small population mate with one another • Minimum viable population size- an estimate of the number of individuals needed for long term survival

44. Under Some Circumstances Population Density Affects Population Size • Density-dependent population controls • Predation • Parasitism • Infectious disease • Competition for resources

45. Several Different Types of Population Change Occur in Nature • Stable • Irruptive • Cyclic fluctuations, boom-and-bust cycles • Top-down population regulation- predation • Bottom-up population regulation – scarcity of a resource. • Irregular

46. Population Cycles for the Snowshoe Hare and Canada Lynx

47. Humans Are Not Exempt from Nature’s Population Controls • Ireland • Potato crop in 1845 • Bubonic plague • Fourteenth century • AIDS • Global epidemic

48. Case Study: Exploding White-Tailed Deer Population in the U.S. • 1900: deer habitat destruction and uncontrolled hunting • 1920s–1930s: laws to protect the deer • Current population explosion for deer • Lyme disease • Deer-vehicle accidents • Eating garden plants and shrubs • Ways to control the deer population

49. 5-4 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? • Concept 5-4 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

50. Communities and Ecosystems Change over Time: Ecological Succession • Natural ecological restoration • Primary succession • Starting from scratch • Secondary succession • Soil in existence (“natural re-purposing”) • Ecosystem has been: • Disturbed (human development spreads) • Removed (draining wetlands) • Destroyed (forest fire)