Notes: Chapter 6 Ecological Communities

1. Notes: Chapter 6 Ecological Communities Competition Evolution Symbiosis Trophic Structure Disturbances Response to Disturbances Biomes

6. Hierarchy of Systems • Biosphere • Biome • Ecosystem (Abiotic & Biotic • Community • Population • Individual

7. Community Ecology - • A study of the interactions between populations of different species and same species in an ecosystem

8. Why we study Ecological Communities • Capture energy and nutrients. Change inorgainic molecules into organic molecules CO2 H2O NO3 O2 Carbohydrates , Protein • Distribute energy and nutrients (Food Web) • Recycle nutrients (matter, not energy) • Control Populations

9. Niche vs. Habitat • Niche- Role or function • The functional role in an ecosystem • “What the organism does for the Community • Ex: Producer, Decomposer, agent of transpiration, • Habitat- Conditions • Where the organism lives • The biotic and abiotic conditions • The landscape • Ex: Tall trees, Rocky mountains, dry

10. Community Structure • Trophic Levels • Producers, Autotrophs • Consumers, Heterotrophs • Primary, Secondary, Tertiary

11. Trophic Levels

12. Producers: the first trophic level • Autotrophs (“self-feeders”) = organisms that capture solar energy for photosynthesis to produce sugars • Green Plants • Cyanobacteria • Algae • Chemosynthetic bacteria use the geothermal energy in hot springs or deep-sea vents to produce their food

13. Energy is converted to biomass • Productivity = rate at which ecosystems generate biomass • Primary production = conversion ofsolar energy to chemical energy by autotrophs • Gross primary production (GPP) = assimilation of energy by autotrophs • Net primary production(NPP) = energy remaining after respiration, and is used to generate biomass • Available for heterotrophs • Secondary production = biomass generated by heterotrophs

14. Consumers: organisms that consume producers Primary consumers = second trophic level • Organisms that consume producers • Herbivores consume plants • Deer, grasshoppers • Secondary consumers = third trophic level • Organisms that prey on primary consumers • Carnivores consume meat • Wolves, rodents

15. Consumers occur at even higher trophic levels • Tertiary Consumers = fourth trophic level • Predators at the highest trophic level • Consume secondary consumers • Are also carnivores • Hawks, owls • Omnivores = consumers that eat both plants and animals

16. Detritivores and decomposers • Organisms that consume nonliving organic matter • Enrich soils and/or recycle nutrients found in dead organisms • Detritivores = scavenge waste products or dead bodies • Millipedes • Decomposers = break down leaf litter and other non-living material • Fungi, bacteria • Enhance topsoil and recycle nutrients

17. Food Web/Energy Web

18. Food webs show relationships and energy flow • Food chain = the relationship of how energy is transferred up the trophic levels • Food web = a visual map of feeding relationships and energy flow • Includes many different organisms at all the various levels • Greatly simplified; leaves out the majority of species

19. Pyramids • Energy Pyramid • Biomass Pyramid • Pyramid of Numbers • GPP/NPP • 10% Rule

20. Pyramids of energy, biomass, and numbers

21. Pyramid of Numbers

22. Sometimes Pyramids are not regular

23. Irregular Pyramid of Numbers

24. Comparison of Pyramids

25. Energy, biomass, and numbers decrease • Most energy organisms use is lost as waste heat through respiration • Less and less energy is available in each successive trophic level • Each level contains only 10% of the energy of the trophic level below it • There are far fewer organisms at the highest trophic levels, with less energy available A human vegetarian’s ecological footprint is smaller than a meat-eater’s footprint

26. Niche • Fundamental Niche- the niche a population of one species could fill if there is no competition. • Realized Niche- the niche a population of one species ends up filling after competition. • Resource Partitioning- adaptations that enable competing species to divide a resource in order to reduce the energy required for direct competition. (Galapagos Island Finch Beaks, becoming nocturnal)

27. Niche: an individual’s ecological role • Fundamental niche = when an individual fulfills its entire role by using all the available resources • Realized niche = the portion of the fundamental niche that is actually filled • Due to competition or other species’ interactions

28. Resource partitioning • Resource partitioning = when species divide shared resources by specializing in different ways • Ex: one species is active at night, another in the daytime • Ex: one species eats small seeds, another eats large seeds

31. Niche • Competitive Exclusion Principle • Resource Partitioning • Video describing the historic change of the competitive exclusion paradigm into the resource partitioning paradigm • http://www.youtube.com/watch?v=LBFnJtTkV4c&safe=active

32. Competition and Evolution • Competition leads to evolution and adaptations- • Random mutations enable some species to compete more successfully and those “mutants” survive and reproduce in greater numbers.

33. Natural selection • Natural selection leads to evolution of adaptations that make predators better hunters • Individuals who are better at catching prey: • Live longer, healthier lives • Take better care of offspring • Predation pressure: prey are at risk of immediate death • Prey develops elaborate defenses against being eaten

34. Organisms evolve defenses against being eaten

35. Coevolution • Coevolution = hosts and parasites become locked in a duel of escalating adaptations • Has been called an “evolutionary arms race” • Each evolves new responses to the other • It may not be beneficial to the parasite to kill its host

36. Keystone Species • Keystone species have a greater and far reaching impact on the community • Keystone species are usually top predators • Removal of a keystone species has a ripple effect called “Trophic Cascade”

37. Some organisms play big roles • Keystone Species =has a strong or wide-reaching impact far out of proportion to its abundance • Removal of a keystone species has substantial ripple effects • Alters the food chain

38. Species can change communitieshttp://www.youtube.com/watch?v=_IWw8Ruz8Uo&safe=active 4min • Trophic Cascade = predators at high trophic levels can indirectly affect populations of organisms at low trophic levels by keeping species at intermediate trophic levels in check • Extermination of wolves led to increased deer populations, which led to overgrazed vegetation and changed forest structure • Ecosystem engineers = physically modify the environment • Beaver dams, prairie dogs, fungi

39. Types of Community Relationships • The term symbiosis (from the Greek sym, meaning "together" and bios, meaning "life") refers to the members of two different species (i.e., two populations) having some sort of ecological interaction that affects both populations

40. Co-existence (Symbiosis) • Exploitation/Antagonistic (- +) • Predation • Herbivory • Parasitism • Mutualism (+ +) • Commensalism (+ 0) • Neutralism (0 0) • Amensalism (- 0)

41. Competition • Interspecific Competition- Competition between different species • Intraspecific Competition- competition between members of the same species • Competitive Exclusion- When competition results in one species competing so successfully that the competing species is killed off or leaves the ecosystem.

42. Effects of predation on populations • Increased prey populations increases predators • Predators survive and reproduce • Increased predator populations decrease prey • Decreased prey population causes starvation of predators • Decreased predator populations increases prey populations • Negative Feedback Loop

43. Effects of zebra mussels • Zebra mussels eat phytoplankton and zooplankton • Both populations decrease in lakes with zebra mussels • They don’t eat cyanobacteria • Cyanobacteria Population increases in lakes with zebra mussels • Zebra mussels are becoming prey for some North American predators: • Diving ducks, muskrats, crayfish, flounder, sturgeon, eels, and carp populations are increasing.

44. Parasites • Parasitism = a relationship in which one organism (parasite) depends on another (host) for nourishment or other benefit • Does not kill the host (That’s why is isn’t a predator-prey) • Some species live within the host • Disease, tapeworms • Others are free-living, and have infrequent contact with their hosts • Ticks, sea lampreys Obligate – requires the host for some part of its life cycle Facultative – doesn’t require the host

46. Herbivory • Exploitation in which animals feed on the tissues of plants • Widely seen in insects • May not kill the plant, but affects its growth and survival • Defenses against herbivory include • Chemicals: toxic or distasteful parts • Physical: thorns, spines, or irritating hairs • Other animals: protect the plant

47. Disturbances in Communities

48. Types of Disturbances: • Floods • Storms and Hurricanes • Fires • Glaciers • Volcanoes • Invasive Species • Human Developments • Erosion • Toxic Spills • ETC.

49. Invasive Species • Species that are native to another community. • These species usually don’t have natural predators or other limiting factors found in their native habitat so they can easily overpopulate and take over the niche of native species, causing biodiversity loss. • 5 worst invasive species 10 min http://www.youtube.com/watch?v=ai33osYTwyI&safe=active

50. Case Study: Zebra Mussels