Section 13-3

Food Chains: sequence of organisms related to one another as food and consumer

Food Webs: interconnecting food chains in an ecological community

Organisms need more than just energy to survive; they also need nutrients

Nutrients: substances organisms use to build living tissue and to grow

Primary producers (Autotrophs)use solar energy and elements in soil to

make their own nutrients Consumers (Heterotrophs)

cannot make their own nutrients they MUST eat other organisms to obtain

them: Herbivores: plants Carnivores: meat Omnivores: plants & meat Decomposers: dead/decaying plant & animal

matter Parasites: live in/on “host” organism

Used to show how energy flows through ecosystem

As move up each level:Only 10% energy is

available for next levelThe # organisms

decreasesThe Biomass (total

weight of living matter) decreases

1. What is a population? 2. Name two factors that effect

population.

Only available in fixed amounts

Must be recycled throughout biosphere

Nutrient Cycle: path along which nutrients are passed from one organism to another and from one part of the biosphere to another

1) Water evaporates from earth into atmosphere (water vapor)

2) Water is cooled, and condenses (liquid)3) Clouds form from water & particles in the

air4) Water falls back to earth as precipitation (rain, snow, etc.)

Nitrogen Fixation: bacteria convert nitrogen in atmosphere to usable form1) Nitrogen is used to make amino acids

(proteins) for plants2) Heterotrophs eat plants, die, and

decompose3) Nitrogen returned to atmosphere by

bacteria and photosynthesis

1) Atmospheric CO2 is used by plants during photosynthesis

2) CO2 is produced by all organisms during cellular respiration