feeding relationships

The first trophic level contains producers. These are mainly plants that produce their own carbon compounds through photosynthesis.

A producer is an organism that can produce its own carbon compounds, e.g. glucose, by chemical processes such as photosynthesis.

A primary consumer is an organism that eats producers. Primary consumers are also known as herbivores.

False. The second trophic level contains primary consumers, which are herbivores that feed on producers. Secondary consumers are found at the* third* trophic level.

A secondary consumer is an organism that eats primary consumers.

False. Herbivores are primary consumers. Secondary consumers eat primary consumers, making them carnivores.

The third trophic level contains secondary consumers, which are carnivores or omnivores that feed on primary consumers.

Tertiary consumers are organisms that feed on secondary consumers. They are carnivores and are present at the fourth trophic level of food chains.

Decomposers are organisms that break down dead and waste material, e.g. bacteria and fungi

True. Decomposers do not fit into any particular trophic level, as they can feed on waste or dead organisms from any part of a food chain.

Food chains show the transfer of energy from one organism to the next.

True. Producers absorb light energy from the sun, converting it into stored chemical energy which passes up the food chain. There are one or two very unusual exceptions to this rule, e.g. food chains that gain energy from chemicals.

Food webs show networks of interconnected food chains that show the interdependence between organisms in an ecosystem.

An increase in a population of primary consumers in a food chain might have the following effects:

A pyramid of numbers shows how many organisms are present at each level of a food chain.

False. Pyramids of numbers are not always pyramid-shaped. This is because large producers, e.g. trees may be present in small numbers at the base of a food chain.

Pyramid of biomass show the mass of living material present at each stage of a food chain.

True. Pyramids of biomass are always pyramid-shaped, regardless of what the pyramid of numbers for that food chain looks like.

A pyramid of energy illustrates the stored chemical energy contained within the biomass of organisms at each trophic levels of a food chain.

Rules that should be followed when drawing pyramids of numbers, biomass or energy include:

Energy enters food chains by the process of photosynthesis; light energy from the sun is converted into stored chemical energy in the tissues of producers,

Energy is transferred up food chains when organisms consume the tissues of other organisms.

False. While some of the chemical energy stored in the producer is transferred to the biomass of the primary consumer when it is eaten, much of it is transferred elsewhere, e.g. to the environment as heat or in waste products

The biological molecules in the tissues of a primary consumer are broken down during digestion, after which some of them may be used to build the biomass of the secondary consumer and some will be lost in waste products.

Approximately 10 % of the stored chemical energy at each trophic level is passed on to the next.

Energy is lost at each trophic level because:

False. When energy is transferred to new biomass it is stored in the tissues; this stored chemical energy is available to the next trophic level.

Food chains are rarely made up of more than five trophic levels because of the energy losses at each trophic level; the total energy available eventually becomes too small to support another trophic level.

True. Energy losses at each trophic level mean that each subsequent trophic level will contain less stored energy in the form of biomass.