Roles of Living Things All organisms need energy to live. In ecosystem, energy moves in ONE direction: Sun Organisms Energy from sun enters ecosystem via PHOTOSYNTHESIS! Organisms gather food by: Producing, Consuming, Decomposing Producers Producers: organisms that make their own food using the suns energy. Produce sugar using carbon dioxide, sunlight and water (in a process called Photosynthesis). Examples: plants, algae, some bacteria. Consumers Consumers: organisms that cannot make their own food. Must eat other organisms. Examples: fungi, many protists and bacteria, animals. 4 ways consumers gather food: 1.Herbivores 2. Carnivores 3. Omnivores 4.Scavengers Herbivores: only eat plants; called primary consumers. Examples: many insects and birds, grazing animals (cows, buffalo, antelope). Carvivores: eat herbivores or other carnivores (eat animals); called secondary or tertiary consumers. Examples: lions, snakes, hawks, spiders. Omnivores: eat plants and animals; could be primary, secondary or tertiary consumers. Examples: humans, bears, chimpanzees. Scavengers: feed on the bodies of dead plants or dead animals; secondary, tertiary or higher consumer. Return nutrients to the environment. Examples: vultures, hyenas, many insects. Decomposers Decomposers: bacteria and fungi that consume the bodies of dead plants and animals or other organic waste. Recycle nutrients back into environment. Trophic Levels Trophic Level: a layer in the structure of feeding relationships in an ecosystem. Levels get smaller and smaller. Producers Autotrophs: make their own food. Puts energy into the ecosystem. Consumers Heterotrophs: cannot make own food, must obtain nourishment by eating other organisms. Interdependence when organisms depend on each other Changes in population of one organism affect all other organisms in the ecosystem. Food Chain: a series of organisms that transfer food between the trophic levels of an ecosystem. Producers herbivores carnivores decomposers Food Web: a network of food chains representing feeding relationships among organisms in an ecosystem. More complex and more realistic. Show interdependence of organisms. Biological Magnification Humans affect environment-add pollution. This is magnified in a food web. The higher up the trophic levels you look, the more pollution you will find (it accumulates). Example: DDT and bald eagles. Biological Magnification: the increasing concentration of a pollutant in organisms at higher trophic levels in a food web. Energy in the Ecosystem Energy from sun enters ecosystem via photosynthesis. Energy then passed from producers to consumers. No food = no survival. Amount of energy available limits the structure of the food web. Energy and Food Producers absorb only 1% of sunlight that reaches earth. Energy used to make cells. Biomass: total amount of organic matter present in a trophic level. Much of energy in each level is lost before it can reach following level (power the animal, in the form of heat, to make shells, fibers, bones, etc) Only 10% energy transfer. Limits the length of food chains. Ecological Pyramids Ecological Pyramid: diagram that shows amount of energy in different trophic levels in ecosystem. Can show energy, biomass, number of organisms in each level. Producers are on the bottom (largest level). Tertiary consumer are on the top (smallest level). Growth of producers limited by lack of elements (carbon, hydrogen, nitrogen, oxygen) not by energy from the sun. Chemical Cycles Most important elements: oxygen, carbon, hydrogen, nitrogen. Elements must be in form cells can use. Three important cycles: 1. Water Cycle 2. Carbon Cycle 3. Nitrogen Cycle Water Cycle Movement of water between ocean, the atmosphere, and the land. Parts of the water cycle: Evaporation (Transpiration) Condensation Precipitation Runoff Evaporation: movement of water into the atmosphere as it changes from liquid to gas. Transpiration: evaporation of water from leaves of plants. Condensation: change of water from gas to water as it cools; leads to formation of clouds. Precipitation: the product of condensation falling to the earth in the form of rain, snow, sleet, hail, etc. Runoff: water flowing downhill and eventually returning to the ocean. Carbon Cycle Movement of carbon from the atmosphere, into the food chain, into the environment and back into the atmosphere. Photosynthesis and Respiration are the most important parts. Photosynthesis uses carbon dioxide and sunlight to make sugars. Respiration breaks down the sugars to remake carbon dioxide and energy. Ocean and rocks are another good source of carbon. Nitrogen Cycle Organisms need nitrogen to make amino acids. Movement of nitrogen from the atmosphere, into the food chain and back into the atmosphere. Steps: Nitrogen-fixing bacteria use nitrogen to make ammonia. Ammonia gets consumed by more bacteria to make nitrogen compounds plants can use. Animals get the nitrogen we need from proteins in the plants we eat. Decomposers return nitrogen to the soil in the form of ammonia.