13a ecology

Click here to load reader

Post on 14-May-2015




3 download

Embed Size (px)


  • 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 forcoevolution
    • 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 anecosystem

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
  • Successionis the process of an ecosystem moving to aclimax communityafter 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 arepioneer 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 movein- 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, calledsymbiotic 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 toniche 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 fishSkimmer- 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
    • http://www.youtube.com/watch?v=z3bWqlPLpMg&feature=BF&list=PLD91727B50EF35272&index=2

18. 19. Predation

  • When one animal eats another
  • Parasitismis 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: doesnt 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 speciesare 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 dont 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 areproducers , because they produce food

30. Role of Organisms

  • Heterotrophs: need a source of organic nutrients, release CO2
  • Calledconsumers , 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


  • 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