ECOSYSTEMS Chapter 47

Levels of Organization Ecologists recognize a hierarchy of organization in the environment: Biosphere Ecosystem Community Population Organism

Levels of Organization The Biosphere The broadest, most inclusive level of organization is the biosphere, the volume of Earth and its atmosphere that supports life. Ecosystems The biosphere is composed of smaller units called ecosystems. An ecosystem includes all of the organisms and the nonliving environment found in a particular place.

Levels of Organization Communities, Populations, and Organisms A community is all the interacting organisms living in an area. Below the community level of organization is the population level, where the focus is on the individual organisms of a single species.

Ecosystem Components Biotic and Abiotic Factors BIOTIC Both biotic (living) factors and abiotic (nonliving) factors influence organisms. BIOTIC Living, or once living, parts of the ecosystem Examples: rabbits, trees, decomposing logs, etc. ABIOTIC Nonliving parts of the ecosystem Examples: Climate, Precipitation, Terrain, Minerals, Nutrients, etc.

The Niche A niche is a way of life, or a role in an ecosystem. Includes an organism’s: Habitat Food sources Predators Competing species Other resources necessary for life

Producers Measuring Productivity Most producers are photosynthetic and make carbohydrates by using energy from the sun. Measuring Productivity Gross primary productivity is the rate at which producers in an ecosystem capture the energy of sunlight by producing organic compounds. Net Primary Productivity: The rate at which biomass accumulates is called net primary productivity. It is equal to the difference between the rate at which the plants in an ecosystem produce useful chemical energy and the rate at which they use some of that energy during respiration.

Consumers Consumers obtain energy by eating other organisms and include herbivores, omnivores, carnivores, detritivores, and decomposers.

Energy Flow Food Chains and Food Webs A single pathway of energy transfer is a food chain. A network showing all paths of energy transfer is a food web.

Energy Transfer Ecosystems contain only a few trophic levels because there is a low rate of energy transfer between each level. The energy transfer from one trophic level to the next is about 10%. About 50% of the food is not digested About 40% of the energy of the food is lost from as heat or used by the organism for cellular respiration making energy for daily life. Only 10% of the food eaten is used for growth and is available as energy to the next trophic level in the food chain.

Trophic Level Trophic levels are the feeding position in a food chain such as primary producers, herbivore, primary carnivore, etc. Green plants form the first trophic level, the producers. Herbivores form the second trophic level, while carnivores form the third and even the fourth trophic levels.

BIOLOGICAL CYCLES The law of conservation of matter, states matter cannot be created/destroyed, although it may be rearranged. Environmental Cycles: A natural process in which elements are continuously cycled in various forms between different compartments of the environment.

The Water Cycle The water cycle traces the pathway that H2O can take through the environment. Key processes in the water cycle are evaporation, transpiration, and precipitation.

The Carbon Cycle The carbon cycle is the series of reactions that move carbon from one place to another in the environment. Photosynthesis and cellular respiration are the two main steps in the carbon cycle.

Nitrogen Cycle Nitrogen-fixing bacteria are important in the nitrogen cycle because they change nitrogen gas into a usable form of nitrogen for plants. The Nitrogen cycle follows the pathway of nitrogen through the environment.

Phosphorus Cycle The phosphorous cycle follows the pathway of phosphorous through the environment. In the phosphorus cycle, phosphorus moves from phosphate deposited in rock, to the soil, to living organisms, and finally to the ocean.