WATCH THIS VIDEO ON Energy Transfer:
Ecosystems are influenced by a combination of biological & physical factors:
–Biological (living) influences are called biotic factors
–Physical (nonliving) influences are called abiotic factors
The area where an organism lives is called its habitat (includes both biotic & abiotic factors).
Autotrophsare organisms that can capture energy from sunlight and use it to produce its own food.Because they make their own food, autotrophs are also called producers. Heterotrophsare organisms that rely on other organisms for their energy and food supply (must EAT).Because they must eat to get energy, heterotrophs are also called consumers.
Energy flows through an ecosystem IN ONE DIRECTION, from the sun to autotrophs (producers) and then to various heterotrophs (consumers).
•The energy stored by producers can be passed through an ecosystem along food chains and food webs.
•A food chain is a series of steps in which organisms transfer energy by eating and being eaten.
•A food web links all of the food chains in an ecosystem together.
Each step in a food chain or web is called a trophic level(trophic means “food or nourishment”).
•Producers make up 1st trophic level – photosynthesis occurs here.
•Consumers make up secondary, tertiary, and higher trophic levels – cell respiration occurs here.
•Each consumer depends on the trophic level below for energy.
•Energy flows in one direction only!
•Only about 10% of the energy available within 1 trophic level is transferred to organisms at the next trophic level – the rest is used up or lost as heat.
The amount of energy or matter in an ecosystem can be represented by an ecological pyramid
•An energy pyramid is a diagram that shows the relative amounts of energy contained within and transferred to each trophic level in a food chain or food web.
Populations in nature are often controlled by predation.
•The regulation of a population by predation takes place within the predator-prey relationship (one of the best known mechanisms of population control).
•In general, the size of the predator population is influenced by the size of the prey population and vice versa.
•If more food is available the predator population will grow, and as the prey population decreases the predator population decrease.