Feeding Relationships (Edexcel IGCSE Science (Double Award): Biology): Flashcards
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- FrontTrophic Levels
Define trophic level.
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Cards in this collection (42)
Define trophic level.
The position of an organism within a particular food chain.
Name the four trophic levels in order.
Producers
Primary consumers
Secondary consumers
Tertiary consumers
Define producer.
An organism at the first trophic level, such as a plant or alga, that converts light energy into chemical energy stored in glucose by photosynthesis.
Define primary consumer.
An organism at the second trophic level that eats producers, transferring chemical energy from plant tissues into its own.
Define secondary consumer.
An organism at the third trophic level that eats primary consumers and gains energy from their tissues.
Define tertiary consumer.
An organism at the fourth trophic level that eats secondary consumers and gains energy from their tissues.
Define decomposer.
An organism, such as bacteria or fungi, that breaks down dead organisms and waste, recycling nutrients back into the ecosystem.
Where do decomposers get their energy from?
From the waste produced at any trophic level, and from organisms that die.
Can one organism occupy more than one trophic level?
Yes. Within a food web an organism can be in several food chains and have a different trophic level in each.
Organisms at the first trophic level are called ＿＿＿＿＿＿＿＿.
Organisms at the first trophic level are called producers.
Bacteria and fungi that break down dead matter are called ＿＿＿＿＿＿＿＿.
Bacteria and fungi that break down dead matter are called decomposers.
True or False?
Producers convert light energy into chemical energy.
True.
They store it as chemical energy in glucose during photosynthesis.
True or False?
A primary consumer eats secondary consumers.
False.
A primary consumer eats producers. It is the secondary consumer that eats primary consumers.
Define food chain.
A diagram showing the energy flow between organisms in an ecosystem. The arrows represent the transfer of energy between trophic levels.
Why do all food chains start with producers?
Because producers convert energy into a form other organisms can use — for example plants convert light energy into chemical energy.
Define food web.
A network of interconnected food chains, showing the complexity of feeding relationships in an ecosystem.
Why can a change in one population affect many others?
Because populations in a food web are interconnected — a change in one alters the food available to, or the predation pressure on, several others.
Give an example of one population change affecting another.
If the number of rabbits falls, the foxes that eat them have less food, so the fox population decreases too.
What does a pyramid of numbers show?
How many organisms are present at each trophic level. The size of each bar indicates the number present.
Why is a pyramid of numbers not always pyramid-shaped?
Because in some food chains many small organisms feed on few large ones — for example many caterpillars on one oak tree.
What does a pyramid of biomass show?
The mass of living organisms present at each trophic level of a food chain.
Why is a pyramid of biomass always pyramid-shaped?
Because the available biomass always decreases at higher trophic levels.
What does a pyramid of energy show, and what shape is it?
The stored energy within the biomass at each trophic level.
It is always pyramid-shaped, because energy is lost at each level.
Give four conventions for drawing a food pyramid.
Keep the trophic levels in food-chain order, with producers at the bottom
Label each bar with its trophic level
Make the bar length reflect the number, biomass or energy
Keep the bars the same height, and draw to scale if graph paper is given
The arrows in a food chain represent the transfer of ＿＿＿＿＿＿＿＿ between trophic levels.
The arrows in a food chain represent the transfer of energy between trophic levels.
A network of interconnected food chains is called a food ＿＿＿＿＿＿＿＿.
A network of interconnected food chains is called a food web.
True or False?
A pyramid of biomass can be an irregular shape.
False.
Pyramids of biomass and energy are always pyramid-shaped. Only pyramids of number can be irregular.
True or False?
A decrease in rabbits could increase grass growth.
True.
With fewer rabbits feeding on it, grass growth increases — which can then increase populations of other grass-eaters such as caterpillars and earthworms.
How does energy enter the first trophic level of a food chain?
Light energy from the sun is converted by producers into chemical energy, stored in carbon-containing compounds within their biomass.
How are energy and substances transferred between trophic levels?
A consumer eats the level below, breaks down the carbon compounds in its biomass, and uses the energy and substances released to build new biomass in its own tissues.
Roughly how much energy is transferred between trophic levels?
Only about 10% of the energy available at each level is converted into biomass at the next.
Why are food chains short?
Because so much energy is lost at each level that the energy available eventually becomes too small to support another trophic level.
Why is energy lost because of what consumers do not eat?
Organisms rarely eat every part of their prey — many predators leave the bones, fur, teeth or claws, so the energy in those parts is never transferred.
Why is energy lost in faeces?
Because not all ingested material is digested and absorbed — plant material in particular is hard to digest and passes out as faeces.
Name three ways absorbed energy fails to become biomass.
Heat loss during respiration and movement
Excretion, for example of urea
Death and decomposition
Give the equation for percentage efficiency of biomass transfer.
percentage efficiency = (biomass in higher trophic level ÷ biomass in lower trophic level) × 100
1450 kg of clover supports 138 kg of snails. What is the efficiency?
(138 ÷ 1450) × 100 = 9.52% to 3 significant figures.
Why can energy efficiency be calculated the same way as biomass?
Because energy is stored within the biomass of an organism, so a loss of energy means a loss of biomass at each trophic level.
Only about ＿＿＿＿＿＿＿＿ of the energy at one trophic level becomes biomass at the next.
Only about 10% of the energy at one trophic level becomes biomass at the next.
Undigested material is lost from a food chain when it is egested as ＿＿＿＿＿＿＿＿.
Undigested material is lost from a food chain when it is egested as faeces.
True or False?
All the energy in one trophic level passes to the next.
False.
Only around 10% is converted into biomass at the next level; the rest is lost as heat, in faeces, in excretion, or in uneaten parts.
True or False?
Respiration causes energy to be lost from a food chain as heat.
True.
Heat lost during respiration and movement is one of the main reasons absorbed energy does not become biomass.
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