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Edexcel Biology GCSE - Organisation of an Ecosystem Part 3

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This deck covers key concepts related to the organisation of ecosystems, including trophic levels, biomass, and energy transfer within food chains.

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The final trophic level is what?

The final level is perch, which is a carnivore and is often called the top or apex predator. Organisms at the tops of food chains have no predators.
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Key Terms

Term
Definition
The final trophic level is what?
The final level is perch, which is a carnivore and is often called the top or apex predator. Organisms at the tops of food chains have no predators.
What are producers?
Green plants - they make glucose during photosynthesis.
What are primary consumers?
Usually eat plant material - they are herbivores. For example rabbits, caterpillars, cows and sheep.
What are secondary consumers?
Eat animal material - they are omnivores or carnivores. For example cats, dogs and lions.
What are predators?
Kill for food. They are either secondary or tertiary consumers.
What are prey?
The animals that predators feed on.
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Edexcel Biology GCSE - Organisation of an Ecosystem Part 3
TermDefinition
The final trophic level is what?
The final level is perch, which is a carnivore and is often called the top or apex predator. Organisms at the tops of food chains have no predators.
What are producers?
Green plants - they make glucose during photosynthesis.
What are primary consumers?
Usually eat plant material - they are herbivores. For example rabbits, caterpillars, cows and sheep.
What are secondary consumers?
Eat animal material - they are omnivores or carnivores. For example cats, dogs and lions.
What are predators?
Kill for food. They are either secondary or tertiary consumers.
What are prey?
The animals that predators feed on.
What are decomposers?
Feed on dead and decaying organisms, and on the undigested parts of plant and animal matter in faeces.
Biomass
Biomass is living or recently dead tissues. The mass of your body is biomass because you are alive. Wood is considered biomass because it was recently a plant. Fossil fuels are not considered biomass because they are the remains of organisms that died millions of years ago and have been chemically changed from the original living tissue.
Pyramids of biomass
The amount of biomass can be measured at different trophic levels in a food chain. The total biomass of each trophic level is often represented as a modified bar chart called a pyramid of biomass. In a food chain from a healthy ecosystem the biomass at each trophic level must reduce. Pyramids of biomass are always perfectly shaped. If this is not the case, then the ecosystem is likely to be unhealthy and in danger.
Pyramids of biomass must be drawn with the:
bars equally spaced around the midpoint bars touching bar for the producer at the bottom length of each bar is proportional to the amount of biomass available at each trophic level
Calculating efficiency of biomass transfers
The efficiency of biomass transfer is a measure of the proportion of biomass transferred from a lower trophic level to a higher one. Usually around 10% of biomass is transferred between trophic levels in a healthy ecosystem and the remaining 90% is used by the organisms during life processes.
This is an example of a food chain: phytoplankton → zooplankton → herring → sea lion The total biomass within the phytoplankton is 14.6 kg. The total biomass within the zooplankton is 1.3 kg. What is the efficiency of this transfer?
To complete this calculation, divide the amount from the higher trophic level by the amount from the lower trophic level and multiply by one hundred. That is, divide the smaller number by the bigger one (and multiply by one hundred). percentage efficiency transfer = (biomass in higher trophic level / /biomas in lower trophic level) x 100 percentage efficiency transfer = (1.3kg/14.6) x 100 = 8.9%
Percentage efficiency transfer equation
percentage efficiency transfer = (biomass in higher trophic level / /biomas in lower trophic level) x 100
What is used for estimating the number of plants?
Quadrat
What is the name of the sampling square used in fieldwork?
Quadrat
A 0.25 m^2 quadrat was placed in a 100 m^2 field. Five daisy plants were counted in the quadrat. What is the estimated number of daisies in the field?
(5/0.25) x 100 = 2000 daisies in the field.
Energy for all food chains comes from what source?
Sun
Producers are usually what?
Plants
How is energy in food chains lost?
Respiration and heat
What happens to the biomass at each stage in a food chain?
Decreases
How do decomposers break materials down?
Using enzymes