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13a ecology


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  • 1. Lecture 13a: Ecology Ecology
  • 2. Ecology
    • Definition: the study of interactions between all of the living and non-living components in an environment
    • So, discussion of ecology can include
      • Animals and plants
      • Soil and water qualities
      • Climate
      • Human impacts
  • 3. Communities
    • Definition: assemblage of populations of multiple species within a single environment
      • Ex: Fallen log
      • Ex: Forest
      • Fairly broad- can be small or large
  • 4. Communities
    • Because the organisms in a community have lived together over a long period of time, opportunity for coevolution
      • When an evolutionary change in one organism influences an evolutionary change in another organism
        • Ex: Many flowers and their pollinators
  • 5. Coevolution
  • 6. Interactions
    • Communities do not exist in a vacuum- the organisms interact with each other and with the environment-- this is an ecosystem
  • 7. Community Composition
    • Species richness : what species make up a community- basically just a list
    • Diversity : richness plus species distribution and relative abundance within the ecosystem
      • If different species spread throughout, more diverse than if only one is abundant
  • 8. Succession
    • Communities change over time- but can take decades to see the changes
    • Succession is the process of an ecosystem moving to a climax community after a disturbance
      • Each particular environment will lead to a stable climax community-a specific assemblage of plants and animals best suited to that environment
  • 9. Primary Succession Occurs when ‘new’ land becomes available- starts from bare rock or sand after glacier retreats, lava flows, etc.
  • 10. Secondary Succession Occurs after a disturbance- fire, agriculture, etc- there is already soil present
  • 11. Succession
    • In either case, first species are pioneer species - small, short-lived, and quick to mature (i.e. weeds)
      • First in primary are lichens and mosses- lichens help break down rocks into soil
    • Gradually, more equilibrium species move in- both plants and animals
  • 12. Ecological Niche
    • Niche : the specific ‘role’ of the organism in the ecosystem, including what it eats, where it lives, when it is active, how it interacts with others
    • Habitat : the part of the ecosystem that the organism in question lives in
      • Ex: Ecosystem for hippos is African savanna, habitat is the river and surrounding shorelines
  • 13. Interactions
    • Organisms interact with each other constantly, both within and outside of their species
    • Interactions, called symbiotic relationships , can be either positive or negative for each
  • 14. Competition
    • Competition can be for food, space, nutrients
    • Competitive exclusion principle : no two species can occupy the same niche at the same time
      • Leads to niche specialization , a way to reduce competition where different species use different resources, even though both could potentially use the same one
  • 15. Competition
    • Character displacement - organisms that have partitioned resources will evolve to suit their acquired niche, and thus the characteristics in question will become more different over time
      • Ex: bird beaks in birds that eat different foods
  • 16. Character displacement Spoonbill-uses bill like a shovel in sand Pelican- catches fish under water Heron- stabs larger fish Skimmer- uses bottom bill to scoop fish from surface
  • 17. Mutualism
    • A relationship in which both members benefit
    • Also very important
      • Ex. plants and pollinators
      • Ex. lichens (algae and fungus, living together)
      • Ex. Ants and caterpillars
  • 18.  
  • 19. Predation
    • When one animal eats another
    • Parasitism is a form of predation in which the predator lives in or on the prey, called the host
    • Ex: cheetahs and gazelles
    • Ex: owls and moles
    • Ex: hookworm and humans!
  • 20. Commensalism
    • Relationship when one organism benefits and the other is neutral
      • Ex: One animal transports another
      • Ex: Sea anemones and clown fish
  • 21. Fish: gets protection from predators Anemone: doesn’t care
  • 22. Name That Relationship! Microhylid frog + tarantula?
  • 23. Name That Relationship! Hermit crab + sea anemone
  • 24. Name That Relationship! Ants + acacia trees
  • 25. Name That Relationship! Cerambycid beetle + pseudoscorpion
  • 26. Community Stability
    • Really, communities are fragile, not stable- stability is hard to achieve because of natural disasters, human encroachment, etc.
    • Keystone species are species that help to stabilize community, other species’ survival can depend on this one species
      • Frequently not abundant
      • Ex: grizzly bears
      • Ex: bats in tropical forests
  • 27. Keystone Species: Sea Otter
    • Sea otters live in kelp forests
    • Eat lots of sea urchins, keep populations low so urchins don’t eat all the kelp
    • However, fishermen want to remove otters because they also eat abalone
    • But, if all otters are gone kelp forest will be gone and abalone will be gone because urchins will eat all the kelp and destroy the ecosystem
  • 28.  
  • 29. Role of Organisms
    • How an organism feeds is part of its niche:
      • Autotrophs: take in inorganic nutrients (CO2, minerals) and outside energy source
        • Plants, algae
    • These organisms are producers , because they produce food
  • 30. Role of Organisms
    • Heterotrophs: need a source of organic nutrients, release CO2
    • Called consumers , because they consume food
    • Four types:
      • Herbivores: eat plants
      • Carnivores: eat other animals
      • Omnivores: eat both plants and animals
      • Detritivores: decompose wastes and dead material
  • 31. Energy and Chemical Flow
    • Solar energy enters ecosystem through plants
    • Plants convert this into chemical energy via photosynthesis
    • Chemical energy is used by animals
  • 32.
    • At each level, some energy is used, some lost as heat
    • Less energy is available to the next level
  • 33. Chemical Cycles
    • Plants use nutrients in the soil to make organic compounds
    • Animals eat the plants and use those compounds
    • When animals die or eliminate waste, nutrients are broken down by detritivores and returned to soil, available to plants again
  • 34.  
  • 35. Food Webs and Energy/ Chemical Flow
    • Food webs represent energy flow from Producers to Primary Consumers to Secondary and Tertiary Consumers
    • Can also be drawn to represent detrital food webs, showing what eats waste
    • Important to realize where energy is stored- may be in living matter (rainforests) or in dead materials (temperate forests)
  • 36.  
  • 37.  
  • 38. Trophic Levels
    • There are always fewer consumers than there are producers, because energy is always lost as heat and used for cellular respiration and growth in every organism
    • As a general rule, only 10% of energy in one level is available to the next
  • 39.  
  • 40. Another way to see it
    • Biomass: it takes 10,000 g of grass to support 10g of snake
  • 41. Primary Productivity
    • Rate at which producers capture and store energy
    • Depends on species, temperature, moisture, soil
    • Highest in tropical environments, lowest at high altitudes, tundra, desert
    • Think of how this relates to high species richness and diversity in tropical rainforest vs. tundra
  • 42. Rainforest
  • 43. Tundra