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13a ecology

13a ecology






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    13a ecology 13a ecology Presentation Transcript

    • Lecture 13a: Ecology Ecology
    • 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
    • Communities
      • Definition: assemblage of populations of multiple species within a single environment
        • Ex: Fallen log
        • Ex: Forest
        • Fairly broad- can be small or large
    • 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
    • Coevolution
    • Interactions
      • Communities do not exist in a vacuum- the organisms interact with each other and with the environment-- this is an ecosystem
    • 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
    • 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
    • Primary Succession Occurs when ‘new’ land becomes available- starts from bare rock or sand after glacier retreats, lava flows, etc.
    • Secondary Succession Occurs after a disturbance- fire, agriculture, etc- there is already soil present
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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!
    • Commensalism
      • Relationship when one organism benefits and the other is neutral
        • Ex: One animal transports another
        • Ex: Sea anemones and clown fish
    • Fish: gets protection from predators Anemone: doesn’t care
    • Name That Relationship! Microhylid frog + tarantula?
    • Name That Relationship! Hermit crab + sea anemone
    • Name That Relationship! Ants + acacia trees
    • Name That Relationship! Cerambycid beetle + pseudoscorpion
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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)
    • 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
    • Another way to see it
      • Biomass: it takes 10,000 g of grass to support 10g of snake
    • 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
    • Rainforest
    • Tundra