 Photosynthesis – energy from the sun enters an ecosystem when a plant uses sunlight to make sugar molecules.  From Producers to Consumers ◦ A producer is an organism that makes its own food.  Also called autotrophs. ◦ A consumer is an organism that gets its energy by eating other organisms.  Also called heterotrophs. ◦ All organisms get their energy from the sun.  An exception to the rule: deep ocean ecosystems ◦ Exist in total darkness – photosynthesis does not occur  Bacteria – use hydrogen sulfide (thermal vents) to produce food.

 Herbivores – plant eaters – rabbit  Carnivores – flesh eaters – tiger  Omnivores – plant and flesh eaters – bear  Decomposers – break down dead organisms – bacteria and fungi

 The process of breaking down food to yield energy.  Reverse the equation for photosynthesis.  Sugar and oxygen yield carbon dioxide, water and energy.  Use this energy to walk, breathe, play sports, ride bikes  Excess energy is stored as fat.

 Each time an organism eats another organism, a transfer of energy occurs.  Food chain – a sequence in which energy is transferred from one organism to the next as each organism eats another organism.  Food Web – shows many feeding relationships that are possible in an ecosystem.  Trophic levels – each step through which energy is transferred in a food chain.

 Energy Pyramids – each layer represents one trophic level.  How Energy Loss Affects an Ecosystem 1.Because so much energy is lost = fewer organisms at higher trophic levels  Zebras and other herbivores outnumber lions on the African savanna by about 1,000 to 1. 2.Loss of energy limits number of trophic levels  Ecosystems rarely have more than 4 or 5 trophic levels

 Plants takes CO 2 from atmosphere and make carbohydrates during photosynthesis – consumers eat producers – undergo cellular respiration some carbon released back into atmosphere as CO 2. ◦ Fossil fuels are made up of carbon compounds from the bodies of organisms that died millions of year ago.  How Humans Affect the Carbon Cycle – burning fossil fuels leads to increased levels of CO 2 – global warming

 Nitrogen Cycle 1.Plants and animals need nitrogen to make protein.  Bacteria on the roots of plants change nitrogen in air to useful form for plant. 2.Living things die – decompose – nitrogen to nitrates 3.Nitrates left in soil – used by plants as source of nitrogen 4.Some nitrates in soil changed back into nitrogen gas by plants. Released into air. 5.Cycle repeats

 Ecological Succession – a gradual process of change and replacement of some or all of the species in a community. ◦ Primary Succession – occurs in places where an ecosystem has never existed.  Rocks or sand dunes ◦ Secondary Succession – the process that begins in an ecosystem when something has disturbed or destroyed the natural community.  Abandoned farmlands, burned or cut forests, heavily polluted streams, floods

◦ Pioneer species – first to establish itself at the start of succession.  Colonizes area – breaks down rock – forms soil – dies – adds nutrients to soil. ◦ Climax community – one that forms in last stages of succession  Oak-hickory forest of PA

 1988 – lightning strikes started fires ◦ Burned about 36% of forest – 2.2 million acres ◦ Secondary succession occurred

 Erupted in May 1980  Burned thousands of acres of surrounding forest.  Secondary succession