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Transcript
Introduction to Ecology • Organisms • Populations – actually interbreeding organisms • Communities – interacting species • Ecosystems – interacting species and their inorganic environment • Biosphere – The thin skin of living space on the earth What sustains Life on Earth? • One-way flow of energy THERE ARE NO ENERGY CYCLES ON EARTH!!!!! Energy has a oneway trip from the sun, through the biosphere and out into space • Cycling of Matter Bucky Fuller was right! We live on a spaceship. There will be no more materials added. Spaceship Earth • Buckminster Fuller coined the term “spaceship earth” • We are on a lightpowered spaceship – Nothing is added but energy – Implication is that resources are finite The Sun is the source of Energy that drives the biosphere • Ultimate source is thermonuclear reactions in sun • The sun is a huge, self- sustaining hydrogen bomb • Good thing that is it 93,000,000 miles away 1 What Happens to Solar Energy Reaching the Earth? • Most is reflected back into space • The rest is used to drive materials (biogeochemical) cycles • Constant energy input from sun keeps biosphere functioning Energy Transfer Within the Biosphere Ray Lindeman • Applied the ideas of physics to ecology • Organisms transfer energy – But energy is lost at each step • Result is food chain Representative Food Chain Food chain – Animals and plants pass energy between each other – Plant gets energy from sun • Fixes Carbon to make sugar • Primary producers (1st trophic level) – Animals get energy from plants • Primary Consumers (2nd trophic level, herbivores) • Secondary Consumers (3rd trophic level, carnivores) • Tertiary Consumers (4th trophic level, top carnivores) – Detritivores eat the left-overs Decomposers and Detritivores Recycle Materials About 10% of the Energy from one trophic level is available to the next level The other 90% is lost as heat This is ecological efficiency 2 Antarctic Ocean Food Web Illinois Forest Food Web • Food Webs are more likely than food chains • The trophic status story still holds Pyramid of Energy Flow • 2nd Law of Thermodynamics says that energy is lost at every transfer • Less and less biomass as you go up the food chain Implications of Pyramid of Energy • You can support more humans as vegetarians than as carnivores – You don’t lose as much energy to lower trophic levels • Food Chains tend to be short • It is easier to exploit low trophic level organisms than high trophic level ones – High trophic level organisms are more likely to be hunted to extinction Feeding Humpback Whales Biogeochemical Cycling Whales are large animals that feed low on the food chain 3 All Material Cycles in Biosphere • Biogeochemical Cycling causes chemicals to turn up in unexpected places • Nutrients – Nitrogen – Phosphorus – Sulfur – Methyl Mercury and Minamata disease – Discharges of methyl mercury taken up by fishes – Caused horrible disease in people and cats • Toxicants also cycle – Dioxin – DDT – Mercury – Lead Species Minamata Bay Mercury Concentrations In sediment from Minamata Bay Robert MacArthur • Biological Species Concept - Interbreeding or potentially interbreeding populations • Ecological Niche – What a species does in the environment • Demonstrated that each species has its own ecological niche • MacArthur’s Warblers 4 MacArthur’s Warblers • All Live together in the same woods • They do different things • Species are selected to do different things in the environment • Fill an ecological niche Ecological Niche • The total way of life or role of a species in an ecosystem. It includes all physical, chemical, and biological conditions as species needs to live and reproduce • Species have environmental tolerances • They “fit” particular environments • If you change the environment, you may cause the species to go extinct The ecological niche of an organism depends not only on where it lives but also on what it does. By analogy, it may be said that the habitat is the organism’s “address”, and the niche is its “profession”, biologically speaking E.P. Odum • You can see the ecological niche as a species role in an ecosystem • Niches may be “broad” or “narrow” – Broad – Rats – Narrow • Red Cockaded Woodpecker • Spotted Owl • Panda 5 Biodiversity • Earth is home to a wide range of species • They keep ecosystems functioning • Why is Biodiversity important – Natural world provides us with food, fiber, energy – Free recycling – Water and Air purification – Natural Pest control Problem of Loss of Biodiversity • Threatens “ecosystem services” • Airplane rivets analogy • Extinction and species endangerment are real problems • So, is the problem of endangered species one that we should worry about??? Winds on a Rotating Earth Earth Ecosystems Climatic Zones of the Earth Biological Communities on Earth organized into “Biomes” • Groups of organisms with similar environmental requirements live together 6 Lots of Different Kinds of Biomes Deciduous Forest Populations Illinois Praire Lake Tundra Rainforest • Population growth could be very fast – There are more babies of most animals (and plants) born than could ever be accomodated on earth • Exponential growth – Can’t continue forever • Limits to growth – Space – Food – Nest Sites • Sheep in Tasmania – Illustrate population growth – Initial exponential growth – Reach a carrying capacity Does this Apply to Humans? Is there a limit to human population growth? 7