transfer of energy

Pyramid of Energy

An energy pyramid is a diagram in which each trophic level is represented by a block and the blocks are stacked on top of one another, with the lowest trophic level on the bottom. The width of each block is determined by the amount of energy stored in the organisms at that trophic level. Because of the energy stored by the organisms at each trophic level is about 1/10th the energy stored by the organisms in the level below, the diagram takes the shape of a pyramid.

-third level

At the third level are secondary consumers, animals that eat other animals. These include carnivores and omnivores. Omnivores use the simple sugars and starches stored in plants as food, but they cannot digest cellulose.

decomposer

Bacteria and fungi are known as decomposers because they cause decay.

-second level

Herbivores are at the second level which are animals that eat plants or other primary producers. They are the primary consumers. A herbivore must be able to break down a plant's molecules into usable compounds. However, the ability to digest cellulose is a chemical feat that only a few organisms have evolved. Cellulose is a complex carb found in plants. Most herbivores rely on microorganisms such as bacteria and protists in their gut to help digest cellulose. Humans cannot digest cellulose because we lack these particular microorganisms.

food web

In most ecosystems, energy does not follow simple straight paths because individual animals often feed at several trophic levels. This creates a complicated, interconnected group of food chains called a food web.

Trophic levels-first level

The lowest trophic level of any ecosystem is occupied by the producers, such as plants, algae and bacteria. Producers use the energy of the sun to build energy-rich carbohydrates. Many producers also absorb nitrogen gas and other key substances from the environment and incorporate them into their biological molecules.

Pyramid of biomass

The number of individuals in a trophic level may not be an accurate indicator of the amount of energy in that level. Some organisms are much bigger than others and therefore use more energy. Because of this, the number of organisms often does not form a pyramid when one compares different trophic levels. Ex, caterpillars and other insect herbivores greatly outnumber the trees they feed on. To better determine the amount of energy present in trophic levels, ecologists measure biomass. Biomass is the dry weight of tissue and other organic matter found in a specific ecosystem. Each higher level on the pyramid contains only 10% of the biomass found in the trophic level below it.

food chain

The path of energy through the trophic levels of an ecosystem is called a food chain.

-fourth level

This level is composed of carnivores that consume other carnivores which are called tertiary consumers or top carnivores. Ex is a hawk that eats a snake. Very rarely do ecosystems contain more than 4 trophic levels.

producers

an organism that can make organic molecules from inorganic molecules; a photosynthetic or chemosynthetic autotroph that serves as the basic food source in an ecosystem (organisms that first capture energy, the producers, include plants, some kinds of bacteria and algae. Producers make energy-storing molecules)

omnivores

an organism that eats both plants and animals

herbivores

an organism that eats only plants

consumers

an organism that eats other organisms or organic matter instead of producing its own nutrients or obtaining nutrients from inorganic sources (those organisms that consume plants or other organisms to obtain the energy necessary to build their molecules)

consumers-secondary

animals that eat other animals

predator

animals that eat other animals for food

consumers-tertiary

carnivores that consume other carnivores or top carnivores

consumers-primary

consumers that eat plants

trophic pyramid

how the trophic levels are organized