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Understanding Biodiversity: Key Species Interactions and Population Control Mechanisms

This chapter delves into the intricate world of biodiversity, emphasizing crucial species interactions, such as competition, predation, parasitism, mutualism, and commensalism. It explores case studies, including the endangered Southern sea otter, a keystone species whose presence influences the health of kelp forest ecosystems. The chapter also addresses factors that limit population growth, including biotic potential and environmental resistance, highlighting the delicate balance of ecosystems. Through this exploration, we gain insight into the importance of conserving biodiversity for ecological stability and resilience.

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Understanding Biodiversity: Key Species Interactions and Population Control Mechanisms

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  1. 13e ENVIRONMENTALSCIENCE CHAPTER 5:Biodiversity, Species Interactions, and Population Control

  2. Fig. 5-1, p. 79

  3. Fig. 5-1, p. 79

  4. Homeworkwatch video • http://www.youtube.com/watch?v=Wcy-i_IJH9Y

  5. Core Case Study: Endangered Southern Sea Otter (1) • Santa Cruz to Santa Barbara shallow coast • Live in kelp forests • Eat shellfish • ~16,000 around 1900 • Hunted for fur and because considered competition for abalone and shellfish

  6. Core Case Study: Endangered Southern Sea Otter (2) • 1938-2008: increase from 50 to ~2760 • 1977: declared an endangered species Keystone species: plays a role affecting many other organisms in ecosystem specificallysea otters eat sea urchins that would otherwise destroy kelp forests Kelp forests provide essential habitat for entire ecosystem

  7. Science Focus: Sea Urchins Threaten Kelp Forests (1) • Kelp forests • Can grow two feet per day • Require cool water • Host many species – high biodiversity • Fight beach erosion • Algin

  8. Science Focus: Sea Urchins Threaten Kelp Forests (2) • Kelp forests threatened by • Sea urchins • Pollution • Rising ocean temperatures • Southern sea otters eat urchins • Keystone species

  9. Fig. 5-A, p. 82

  10. 5-1 How Do Species Interact? • Concept 5-1 Five types of species interactions affect the resource use and population sizes of the species in an ecosystem.

  11. Species Interact in 5 Major Ways • Interspecific competition • Predation • Parasitism • Mutualism • Commensalism

  12. In Class Assignment:What are the 5 major ways species interact?Define each • Interspecific competition • Predation • Parasitism • Mutualism • Commensalism

  13. Interspecific Competition • No two species can share vital limited resources for long • Resolved by: • Migration • Shift in feeding habits or behavior • Population drop • Extinction • Intense competition leads to resource partitioning

  14. Blackburnian Warbler Black-throated Green Warbler Cape May Warbler Bay-breasted Warbler Yellow-rumped Warbler Resource Partitioning of 5 species of insect eating warblers Stepped Art Fig. 5-2, p. 81

  15. Predation (1) • Predator strategies • Herbivores can move to plants • Carnivores • Pursuit • Ambush • Camouflage • Chemical warfare

  16. Predation (2) • Prey strategies • Evasion • Alertness – highly developed senses • Protection – shells, bark, spines, thorns • Camouflage

  17. Predation (3) • Prey strategies, continued • Mimicry • Chemical warfare • Warning coloration • Behavioral strategies – puffing up

  18. Ways in which prey species avoid their predators Camouflage (a) Span worm (b) Wandering leaf insect Fig. 5-3, p. 83

  19. Chemical Warfare Warning coloration (c) Bombardier beetle (d) Foul-tasting monarch butterfly Fig. 5-3, p. 83

  20. Chemical warfare; warning coloration Mimicry (e) Poison dart frog (f) Viceroy butterfly mimics monarch butterfly Fig. 5-3, p. 83

  21. Deceptive looks Deceptive behavior (h) When touched, snake caterpillar changes shape to look like head of snake. (g) Hind wings of Io moth resemble eyes of a much larger animal. Fig. 5-3, p. 83

  22. Coevolution • Predator and prey • Intense natural selection pressure on each other • Each can evolve to counter the advantageous traits the other has developed • Bats and moths

  23. Fig. 5-4, p. 83

  24. Parasitism • Live in or on the host • Parasite benefits, host harmed • Parasites promote biodiversity

  25. Fig. 5-5, p. 84

  26. Fig. 5-5, p. 84

  27. Relationships often more complicated than they first seem • Mistletoe a parasite and a keystone species? • http://news.nationalgeographic.com/news/2007/12/071224-mistletoe-research.html

  28. Mutualism • Both species benefit • Nutrition and protection • Gut inhabitant mutualism

  29. Fig. 5-6, p. 85

  30. Fig. 5-6, p. 85

  31. Commensalism • Benefits one species with little impact on other

  32. Fig. 5-7, p. 85

  33. 5-2 What Limits the Growth of Populations? • Concept 5-2 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

  34. Limits to Population Growth (1) • Biotic potential is idealized capacity for growth • Ex. With no controls on pop growth a species of bacteria that can reproduce every 20 minutes would generate enough offspring to form a layer 1 foot deep over the entire earth’s surface in just 36 hrs • Intrinsic rate of increase (r):rate at which a population could grow if it had unlimited resources • Nature limits population growth with resource limits and competition • Environmental resistance: the combination of all factors that act to limit the growth of a population • Carrying capacity: the max pop of a given species that a particular habitat can support indefinitely

  35. Limits to Population Growth (1) • Exponential growth- starts slowly but then accelerates as the pop increases because the base size of the pop is increasing (J shaped curve) • Logistic growth- growth rate decreases as the pop becomes larger and faces environmental resistance ; over time , the pop size stabilizes at or near the carrying capacity of its environment which results in a sigmoid (S shaped) population growth curve

  36. Overshoot and Dieback • Population not transition always smooth from exponential to logistic growth • Overshoot carrying capacity of environment • Caused by reproductive time lag (the time needed for the birth rate to fall and the death rate to rise in response to resource overconsumption) • Dieback (Population Crash), unless excess individuals switch to new resource

  37. Different Reproductive Patterns • r-Selected species • Many, usually small offspring, give them little parental care or protection • These species overcome massive losses of offspring by producing so many that a few will likely survive to begin to reproduce again • K-selected species • Slowly reproducing, reproduce later in life, ex. Mammals offspring develop inside mother’s body’s where they are safe, parents devote much time to care of young • Most species’ reproductive cycles between two extremes

  38. 5-3 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? • Concept 5-3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

  39. Ecological Succession: gradual change in species composition in a given area • Primary succession-involves the gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem • Secondary succession- contains soil or sediment • Disturbances create new conditions

  40. Succession’s Unpredictable Path • Successional path not always predictable toward climax community • Communities are ever-changing mosaics of different stages of succession • Continual change, not permanent equilibrium

  41. Inertia, persistence (the ability of a living system such as a forest or grassland to survive moderate disturbances) • Resilience the ability of a living system to be restored thru secondary succession after a more severe disturbance • Ecological tipping point • Tropical rain forests vs less diverse tropical grasslands

  42. Succession at Mt. St. Helens • http://news.nationalgeographic.com/news/2005/05/0513_050513_mountsthelens.html • http://ngm.nationalgeographic.com/2010/05/mount-st-helens/funk-text

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