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GCSE Biology Summary Notes Energy Transfers
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Summary Notes on the GCSE Biology topic Energy Transfers, specifically curated for the AQA Biology Exam Board.
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Energy TransfersKey Terms
Producer – organism that makes its own food via photosynthesis using light energy.
Primary Consumer – organism that eats other producers, the first consumer in the food
chain.
Secondary Consumer – organism that eats the primary consumer, the second consumer in
the food chain.
Herbivore – organism that eats plants.
Carnivore – organism that eats animals/ meat.
Omnivore – organism that eats plants and animals.
Autotroph – another word for producer, self-feeding, doesn’t have to eat anything else for
energy, only needs the sun’s energy.
Heterotroph – eats any type of consumer.
Tertiary Consumer – organism that eats the secondary consumer, the third consumer in the
food chain.
Apex Predator – the top of the food chain.
Decomposers – microorganisms, fungi or bacteria that cause decay.
Trophic Level – a feeding level in a food chain.
Food Chain
The arrow shows the transfer of energy.
Decomposers do extra-cellular digestion secrete enzymes out of their cells and absorb
nutrients.
Biomass
The mass of material in living organisms. Wet biomass includes the water mass and
dry biomass is true measure of biomass (not including water mass).
Biomass made by plants is passed on through food chains or food webs. It goes into the
animals that eat the plants. It then passes into the animals that eat other animals. But no
matter how long the food chain, the original source of biomass is usually photosynthesis.
, Only 1% of all the energy from light falling on earth is used in photosynthesis and
approximately only 10% of the biomass from each trophic level is transferred to the level
above it.
In a food chain, there are usually more producers than primary consumers and usually more
primary consumers than secondary consumers. But the number of organisms doesn’t
necessarily reflect what is happening to the biomass – the size of the organism matters as
well as the actual numbers.
Photosynthesis is important in the food chain as there would be no glucose produced for
consumer to survive off and for energy transfer down the chain, otherwise there’d be no
light absorption. It also releases oxygens which is beneficial to all organisms.
In producers when light is the wrong wavelength it is reflected, when it passes through the
leaf most absorbed energy is lost for photosynthesis, some absorbed energy is lost as heat
and some is converted to chemical energy.
Pyramid of Biomass
Label with trophic level/name.
Width depends on biomass.
Make is symmetrical.
Use a ruler.
Bars same height.
The length of each bar represents the amount of organic matter – biomass – at each trophic
level in a specified area. At each trophic level, the amount of biomass and energy available is
reduced, giving a pyramid shape.
As we go up the food chain biomass decreases and the energy decreases.
Biomass Loss
Part of biomass is used for cellular respiration which provides energy for living processes.
Some material such as CO2 or H2O is lost as waste products of respiration. So, energy is
transferred so the organism can maintain a constant temperature.
Biomass in as food.
Biomass lost as used to provide energy for movement and growth.
Biomass turned into new biomass.
Biomass lost as faeces. Herbivores can’t digest all the plant material e.g. the enzymes for
cellulose. So, they can’t be broken down and absorbed and are egested. Herbivores lose
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