B10 Energy Flow in Ecosystems
Animals, plants and where they live
What you need to know...
(the numbers in bold are the points from the curriculum...)
1 State that the Sun is the principal source of energy input to biological systems.
2 Define the terms:
food chain as a chart showing the flow of energy (food) from one organism
to the next beginning with a producer (e.g. mahogany tree → caterpillar → song bird → hawk),
food web as a network of interconnected food chains showing the energy flow through part of an ecosystem,
producer as an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis,
consumer as an organism that gets its energy by feeding on other organisms,
herbivore as an animal that gets its energy by eating plants,
carnivore as an animal that gets its energy by eating other animals.
3 Describe energy losses between trophic levels.
4 Define the terms:
decomposer as an organism that gets its energy from dead or waste organic matter,
ecosystem as a unit containing all of the organisms and their environment, interacting together, in a given area, e.g. decomposing log or a lake,
trophic level as the position of an organism in a food chain or food web.
5 Explain why food chains usually have fewer than five trophic levels.
6. Describe the carbon cycle
7. Discuss the effects of combustion of fossil fuels and the cutting down of forests on the oxygen and carbon dioxide concentrations in the atmosphere
But what happens when different organism need the same things? Thats when it starts to get really interesting, but first a quick introduction to see how life fits together and to look at some of the definitions of key words that we need to understand and use in this unit...
Food Chains and Food Webs
Most types of organisms (including organisms) need to get their energy by consuming other plants and animals, these organisms are known as ____________ .
Important words we need to know
Some quick questions
You can think of the word habitat as the address where an animal or plant lives. Name the habitat for:
- Polar bear
What is the difference between a population and a community?
An ecosystem consists of a ___________ and _____________.
A specific part of an ecosystem where one particular type of organism lives is called its ________.
Can you identify the producers, herbivores, carnivores from this diagram?
- Plants are called producers because they make (produce) their own food - glucose molecules.
- Here is a quick reminder of how its done, AND why its so important for organisms that depend on them (like us)
- Consumers are organisms that eat/consume other organisms
- They do not produce their own food.
- Herbivores, carnivores and omnivores are all types of consumers.
Food webs in action
Below is a diagram of a food web, fill in the the arrows to show how energy is moved from producers through to the top carnivores.
Don't forget that the arrows are used to show the flow of energy, so they must point in the direction that the energy moves
They release the nutrients locked inside material such as;
- Leaves and sticks that have fallen from plants and trees
- Dead organisms
Without decomposers so many nutrients would be lost from the environment, watch the short video clip below to find out more...
Five trophic levels
- Energy is lost from each level of the food chain, as energy is used in life processes such as movement, digestion, respiration, faeces.
- Energy is lost as thermal energy from mammals to their surroundings.
- Energy is lost in faeces and urine
- Ultimately, all energy is lost as thermal energy produced by the movement, respiration (and other chemical reactions) and through faeces
All this energy loss means that the higher up the food web you go the less energy is available, this is why food webs can not sustain more than five trophic levels.
Try an exam style question
All energy originally comes from the sun...
Plants use some of this energy, and energy is lost from each level of the food chain
Only about 10% of energy is passed on from each trophic level
Food chains and food webs
The Carbon Cycle
- The carbon cycle shows how carbon containing compounds move around our biosphere.
- Carbon dioxide in the atmosphere is used by plants in photosynthesis, the carbon atoms from CO2 are used to make carbohydrates
- These carbohydrates are then eaten by primary consumers such as herbivores, and also by omnivores. The carbon atoms are now used in respiration to make energy and carbon dioxide. The same carbon atoms are exhaled back into the atmosphere.
- When an organisms dies it is broken down by decomposers. The decomposers use the carbohydrates from the dead organisms in respiration and release the carbon atoms back into the environment as CO2.
- Not all organisms will be broken down by decomposers. Some organisms will decay over millions of years to eventually form fossil fuels. Fossil fuels are a major source of energy and when they undergo combustion they release the carbon that has been trapped for millions of years back into the atmosphere as CO2.
Some of this CO2 is used by plants in photosynthesis and the cycle continues....
How do you think the carbon cycle is affected by deforestation?
- Deforestation increases (so there are less trees doing photosynthesis)
- Combustion increases (more fossil fuels are being burned)
EVERYTHING BELOW IS TRIPLE AWARD ONLY!!!
Coral Reef Ecosystem
Ecological Pyramids (triple award only)
Pyramid of biomass shows the weight (g/m2) of the organisms at each trophic level.
How can we find out about the environment?
We can use a data logger to test various conditions from the environment such as
- carbon dioxide
- levels of oxygen are changing,
- amount of light
- Salinity (how much salt there is in solution)