Energy, Trophic Levels, and Food Webs

producer

(autotrophs) are typically plants or algae. Plants and algae do not usually eat other organisms, but pull nutrients from the soil or the ocean and manufacture their own food using photosynthesis.

decomposer

(bacteria and fungi) break down dead plant and animal material and wastes and release it again as energy and nutrients into the ecosystem for recycling.

consumer

(heterotrophs) are species that cannot manufacture their own food and need to consume other organisms.

how energy is lost after an organism produces or consumes food - what happens to this energy? why does this mean every ecosystem must have a source of energy?

A part of the energy received by primary consumers, herbivores, is converted to body heat (an effect of respiration), which is radiated away and lost from the system. Energy loss also occurs in the expulsion of undigested food. Some energy is lost from the system, since energy which the primary consumers had used for respiration and regulation of body temperature cannot be utilised by the secondary consumers. Most energy is lost, so every ecosystem needs their own energy in case they aren't passed on enough energy

secondary consumer

Carnivores that eat herbivores

tertiary consumer

Carnivores that eat other carnivores

how trophic levels relate to food chains

Food chains start at trophic level 1 with primary producers such as plants, move to herbivores at level 2, predators at level 3 and typically finish with carnivores or apex predators at level 4 or 5.

primary consumer

Plants and algae make their own food

the flow of energy in ecosystems

The energy is passed on from trophic level to trophic level and each time about 90% of the energy is lost, with some being lost as heat into the environment (an effect of respiration) and some being lost as incompletely digested food (egesta). Therefore, primary consumers get about 10% of the energy produced by autotrophs, while secondary consumers get 1% and tertiary consumers get 0.1%. This means the top consumer of a food chain receives the least energy, as a lot of the food chain's energy has been lost between trophic levels.

compare and contrast how autotrophs and heterotrophs obtain food

autotrophs (producers, primary consumer) pull nutrients from the soil or the ocean and manufacture their own food using photosynthesis. Heterotrophs (consumer) Animals that eat primary producers (like plants). Animals that eat other animals. Animals that eat both plant and other animals.

the original source of energy for nearly all ecosystems is and how this energy is captured and converted by all organisms

the sun which is required for photosynthesis