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What type of organism is present at the first trophic level in a food chain?
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What type of organism is present at the first trophic level in a food chain?
The first trophic level contains producers. These are mainly plants that produce their own carbon compounds through photosynthesis.
Define the term producer.
A producer is an organism that can produce its own carbon compounds, e.g. glucose, by chemical processes such as photosynthesis.
Define the term primary consumer.
A primary consumer is an organism that eats producers. Primary consumers are also known as herbivores.
True or False?
The second trophic level of a food chain contains secondary consumers.
False.
The second trophic level contains primary consumers, which are herbivores that feed on producers. Secondary consumers are found at the third trophic level.
Define the term secondary consumer.
A secondary consumer is an organism that eats primary consumers.
True or False?
Herbivores are secondary consumers.
False.
Herbivores are primary consumers. Secondary consumers eat primary consumers, making them carnivores.
What type of organism is present at the third trophic level of a food chain?
The third trophic level contains secondary consumers, which are carnivores or omnivores that feed on primary consumers.
Define the term tertiary consumer.
Tertiary consumers are organisms that feed on secondary consumers. They are carnivores and are present at the fourth trophic level of food chains.
Define the term decomposer.
Decomposers are organisms that break down dead and waste material, e.g. bacteria and fungi
True or False?
Decomposers can feed on dead and waste material from any level of the food chain.
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.
What do food chains show?
Food chains show the transfer of energy from one organism to the next.
True or False?
The source of all energy in a food chain is the sun.
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.
What do food webs show?
Food webs show networks of interconnected food chains that show the interdependence between organisms in an ecosystem.
What effect might an increase in the population of primary consumers have on a food web?
An increase in a population of primary consumers in a food chain might have the following effects:
A decrease in the population of any producers eaten by the population
An increase in the population of any secondary consumers that feed on the population
A decrease in the population of any other primary consumer populations within the food web
What do pyramids of numbers show?
A pyramid of numbers shows how many organisms are present at each level of a food chain.
True or False?
Pyramids of numbers are always pyramid-shaped.
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.
What do pyramids of biomass show?
Pyramid of biomass show the mass of living material present at each stage of a food chain.
True or False?
Pyramids of biomass are always pyramid-shaped.
True.
Pyramids of biomass are always pyramid-shaped, regardless of what the pyramid of numbers for that food chain looks like.
What does a pyramid of energy illustrate?
A pyramid of energy illustrates the stored chemical energy contained within the biomass of organisms at each trophic levels of a food chain.
What rules should be followed when drawing a pyramid of numbers, biomass or energy?
Rules that should be followed when drawing pyramids of numbers, biomass or energy include:
The producers should always be at the base, with each subsequent trophic level in order above this
Each box should be labelled with its trophic level and species
If graph paper is provided then boxes should be drawn to scale
How does energy enter food chains?
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,
How is energy transferred up food chains?
Energy is transferred up food chains when organisms consume the tissues of other organisms.
True or False?
When a primary consumer eats a plant all of the chemical energy stored in the plant is transferred to the biomass of the primary consumer.
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
What happens to the biological molecules, e.g. proteins, in the tissues of a primary consumer when they are eaten by a secondary consumer?
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 what percentage of the energy stored at each trophic level is passed on to the next?
Approximately 10 % of the stored chemical energy at each trophic level is passed on to the next.
What are some reasons for energy loss at each trophic level of a food chain?
Energy is lost at each trophic level because:
Organisms rarely eat every part of the consumed organism
Some tissues cannot be fully digested by consumer so any undigested material is egested in faeces
Energy released from consumed tissues may be used for, e.g. movement, meaning that it is eventually transferred to the environment as heat
Energy is lost in metabolic waste, e.g. urea in urine
True or False?
Energy is lost from food chains when organisms transfer energy to new biomass.
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.
Why are food chains rarely made up of more than five trophic levels?
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 or False?
Pyramids of biomass and energy are always pyramid-shaped due to energy losses between trophic levels.
True.
Energy losses at each trophic level mean that each subsequent trophic level will contain less stored energy in the form of biomass.