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Ecology

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  1. Ecology IB Biology January 2007

  2. What is a species and how many are there? • A species is a group of organisms that resemble one another in appearance, behavior, chemistry, and genetic make-up • The true test to determine if two individuals are members of the same species is to see whether or not viable (fertile) offspring can be produced under natural conditions • We don’t know how many exist on earth • 1.5 to 1.8 million identified • Estimates (save bacteria) are 3 to 100 million • Most common are insects and plants

  3. Each species has a niche • Niche: “role” in the biological community • Includes • range of tolerance to abiotic factors • Types and amounts of resources it uses • Interactions with other species • Habitat: physical location; “address” • Generalist species (broad niche) • Can live in variety of habitats, eat a variety of things, tolerate a wide array of conditions • Flies, cockroaches, deer, raccoons, humans • Specialist species (narrow niche) • Can live in only one or a few habitats, narrow diet, tolerate a narrow range of conditions • More vulnerable to extinction (giant panda)

  4. Lower limit of tolerance Upper limit of tolerance No organisms Few organisms Few organisms No organisms Abundance of organisms Population size Zone of intolerance Zone of physiological stress Optimum range Zone of physiological stress Zone of intolerance Low Temperature High Range of Tolerance Concept

  5. World Vegetation

  6. World Biomes

  7. Basic Climate Pattern

  8. Biotic interactions between species • Inter vs. Intraspecific competition (-,-) • Inter=between species • Intra=within species • Strategies to avoid competition=resource partitioning (eg warblers) • Predation (+,-) • Why is predation important? • Parasitism (+,-) • Parasite usually smaller, gradually weakens host over time, rarely kills its host (why?) • Mutualism (symbiosis) (+,+) • Commensalism (+, no effect) • Epiphytic plants (eg. Orchids)

  9. Fig. 4-1, p. 65 Resource Partitioning in Warblers

  10. Fig. 4-2, p. 66 Mutualism/Symbiosis Coral Reef is another great example

  11. Fig. 4-3, p. 66 Commensalism

  12. Biotic factorWhat’s causing this pattern? High Paramecium aurelia Relative population density Paramecium caudatum Low 0 2 4 6 8 10 12 14 16 18 Days Both species grown together

  13. Biotic factorWhat’s causing this pattern?

  14. Abiotic factorWhat’s causing this pattern?

  15. Energy and Matter Flow:Food Chains and Food Webs • A sequence of organisms, each of which is a source of food for the next, is a food chain • Food Web=network of interconnected food chains • Trophic level=feeding level • e.g., producers=1st trophic level and primary consumer = 2nd trophic level

  16. Heat Abiotic chemicals (carbon dioxide, oxygen, nitrogen, minerals) Heat Solar energy Heat Decomposers (bacteria, fungus) Producers (plants) Consumers (herbivores, carnivores) Heat Heat Ecosystem Components

  17. First Trophic Level Second Trophic Level Third Trophic Level Fourth Trophic Level Primary consumers (herbivores) Secondary consumers (carnivores) Tertiary consumers (top carnivores) Producers (plants) Heat Heat Heat Heat Solar energy Heat Heat Heat Detritvores (decomposers and detritus feeders) Food Chains in Action Why do food chains rarely have more than four trophic levels?

  18. Humans Blue whale Sperm whale Killer whale Elephant seal Crab eater seal Leopard seal Emperor penguin Adélie penguins Petrel Squid Fish Carnivorous plankton Herbivorous zooplankton Krill Phytoplankton Example of a Food Web Note: Arrows Go In Direction Of Energy Flow

  19. Ecological Efficiency • Each trophic level in a food chain or web contains a certain amount of biomass (the dry weight of all organic matter) • In a food chain/web, chemical energy stored in biomass is transferred from one trophic level to the next • The percentage of usable energy transferred as biomass from one trophic level to another is called ecological efficiency • Ranges between 5-20% (i.e., 95 to 80% of energy is lost from one level to the next) • The more trophic levels or steps in a food chain the greater the cumulative loss of usable energy

  20. Heat Heat Tertiary consumers (human) Decomposers Heat 10 Secondary consumers (perch) Heat 100 Primary consumers (zooplankton) 1,000 Heat 10,000 Usable energy Available at Each tropic level (in kilocalories) Producers (phytoplankton) Fig. 2-21, p. 34 Pyramid Of Energy Flow

  21. Energy Input: 1,700,000 kilocalories Incoming solar energy not harnessed 1,679,190 (98.8%) Energy Transfers 20,810 (1.2%) Producers Waste, remains Metabolic heat, export 4,245 3,368 13,197 Herbivores 720 383 2,265 Carnivores 90 21 272 Top carnivores 5 16 Decomposers, detritivores Energy Output Total Annual Energy Flow 20,810 + 1,679,190 1,700,000 (100%) Top carnivores Decomposers/detritivores 21 Carnivores 5,060 383 Herbivores 3,368 Producers 20,810

  22. Why you should eat veggie

  23. Primary and Net Productivity • The RATE at which producers convert solar energy into chemical energy as biomass is the ecosystem’s gross primary productivity (GPP) • But producers also consume energy in order to stay alive (metabolism) • GPP – E consumed by producer = NPP (net primary productivity) • NPP is available for use as food by other organisms in an ecosystem • Measured in grams carbon per meter squared per year (gC/m2/yr) or in kilocalories per meter squared per year (kcals/m2/yr)

  24. NPP of Ecosystems

  25. Primary SuccessionHow is each stage different?

  26. Secondary SuccessionHow is this both similar and different from primary succession?

  27. Early Successional Species Rabbit Quail Ringneck pheasant Dove Bobolink Pocket gopher Midsuccessional Species Elk Moose Deer Ruffled grouse Snowshoe hare Bluebird Late Successional Species Turkey Martin Hammond’s Flycatcher Gray squirrel Wilderness Species Grizzly bear Wolf Caribou Bighorn sheep California condor Great horned owl Ecological succession