1. Cycling of Matter In this presentation you will:
Decomposers release nutrients into the soil
Death and decay
Plants take up the nutrients in the soil
In this presentation you will:
explore energy flow through living systems
explore recycling of matter in living systems
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2. Introduction
An ecosystem is a collection of living things that interact with each other and their environment.
The plants and animals within an ecosystem depend on each other for survival.
In just one ecosystem, there are lots of food chains. A food chain can be used to show the transfer of energy from one organism to another, through the ecosystem, by the process of feeding.
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3. The Origin of Energy
Nearly all of the energy found in the different ecosystems on Earth can be traced back to the Sun. Without energy from the Sun, life could not exist on the planet as we know it.
The Sun gives off energy in the forms of heat and light. Energy from the Sun is known as solar energy.
Plants depend on solar energy.
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4. Photosynthesis Producers are organisms that produce their own food.
Green plants are producers – they convert sunlight into energy (food).
Radiant Energy
They do this by a series of chemical reactions, where radiant energy from the sun reacts with water and carbon dioxide to form chemical energy.
This process is called photosynthesis.
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5. Radiant energy (sunlight)
Producers
Carbon dioxide and water are the “ingredients” for photosynthesis, and sugar (glucose) is formed, along with oxygen.
The plants then use these products to carry out the life processes that enable them to survive.
Water
6 H2O
Carbon dioxide
6 CO2
Radiant energy (sunlight)
Glucose
C6H12O6
Oxygen
6 O2 + +
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6. Energy Transfer
The sugars are rich in chemical energy, and by eating the plants, animals take in the energy from the sugars.
As other organisms, such as snails, feed upon the plants, some of this energy gets transferred to them.
In the same way, the energy from the snail can get transferred to another animal if it is eaten.
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7. Question 1 Where does solar energy come from? A) The Sun
B) Food chains
C) The Moon
D) Plants
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8. Question 1 Where does solar energy come from? A) The Sun
B) Food chains
C) The Moon
D) Plants
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9. Consumers
Consumer organisms cannot make their own food. They need to get their energy by feeding on other organisms.
Some consumers feed only on producers (plants). These consumers are called herbivores.
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10. Consumers
Other consumers feed only on other consumers. These are called carnivores.
Depending on how the different consumers feed, they can be arranged into a food chain, to illustrate how energy gets transferred through the ecosystem.
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11. Producers are at the lowest trophic level of a food chain.
Trophic Levels
The different stages of a food chain are called trophic levels. The levels are arranged in order of who feeds on who.
Producers are at the lowest trophic level of a food chain.
Secondary consumer
Primary consumers are the level above the producers.
Primary consumer
Producer
Secondary consumers occupy the level above the primary consumers.
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12. Trophic Levels
Tertiary consumers are found on the level above the secondary consumers.
Tertiary consumer
Secondary consumer
There are rarely more than five levels in a food chain. The consumer at the highest level is also known as the top predator.
Primary consumer
Producer
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13. Question 2
In a food chain, which of the following would you find on the trophic level immediately above producers?
A) Carnivores
B) The Sun
C) Secondary consumers
D) Primary consumers
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14. Question 2
In a food chain, which of the following would you find on the trophic level immediately above producers?
A) Carnivores
B) The Sun
C) Secondary consumers
D) Primary consumers
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15. Food Chains Arrows in a food chain mean ‘are eaten by’.
When one organism is eaten by another, chemical energy is transferred between them. The direction of the arrow shows the direction of the energy flow.
For example, berries are eaten by small birds. The berries give the birds the energy they need.
A food chain
Small birds are eaten by larger birds of prey. Some energy obtained by small birds, from the berries, gets passed to the larger bird.
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16. Question 3 Look at the food chain picture. Energy is passed from:
A) small bird to berries
B) bird of prey to small bird
C) berries to small bird
D) No energy is passed along the food chain
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17. Question 3 Look at the food chain picture. Energy is passed from:
A) small bird to berries
B) bird of prey to small bird
C) berries to small bird
D) No energy is passed along the food chain
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18. Food Webs
A food web consists of many different food chains. This web contains five food chains that each contain three trophic levels.
Minnows
Dragonfly larvae
Ducks
Tadpoles
Water fleas
Snails
Mosquito larvae
Food webs show the feeding relationships of more species than a food chain does.
Algae on stones
Floating algae
Therefore, they give a more complete view of how energy can move through ecosystems.
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19. Food Webs
Often, if one organism disappears from a food web, other organisms can survive by feeding from different organisms.
Minnows
Dragonfly larvae
Ducks
Tadpoles
Water fleas
Snails
Mosquito larvae
This will, however, affect the number of organisms elsewhere in the web.
Algae on stones
Floating algae
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20. Question 5
Which of the following provides the most complete view of the feeding relationships in an ecosystem?
A) A food chain
B) A food web
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21. Question 5
Which of the following provides the most complete view of the feeding relationships in an ecosystem?
A) A food chain
B) A food web
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22. Number Pyramids
Grass (100,000)
Grasshoppers (50)
Mice (15)
Wild cats (2)
A number pyramid shows the number of organisms that make up each trophic level in a food chain.
In this food chain, the producer is grass.
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23. Number Pyramids
Grass (100,000)
Grasshoppers (50)
Mice (15)
Wild cats (2)
There are many individual grass plants in this food chain. They occupy the largest section of the pyramid.
The broken lines show that the pyramid is not drawn to scale.
As you travel up through the food chain, the number of organisms at each trophic level usually decreases as the organisms increase in size.
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24. Number Pyramids Not all number pyramids have regular pyramid shapes.
Blackbirds (20)
Ladybugs (200)
Greenfly (6000)
Oak tree (1)
Not all number pyramids have regular pyramid shapes.
In this case, a massive single producer (the oak tree) can support many thousands of greenfly.
However, there are fewer ladybugs than greenfly and even fewer blackbirds, so the top of the diagram is still pyramid shaped.
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25. Energy Pyramids
Along the way through a food chain, a large percentage of the energy (about 90%) is lost from one trophic level to the next.
This is because:
Not every living part of an organism is eaten, such as animal skeletons, so the energy contained within these parts cannot be used.
Chemical energy is used by an organism for movement, growth, digestion, reproduction and a number of other processes.
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26. Energy Pyramids
Energy pyramids show the amount of chemical energy that is available at each trophic level of a food chain.
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27. Energy Pyramids
Orange 10,000 J
Oriole 1,000 J
Hawk 100 J
Bobcat 10 J
Energy pyramids take into account the energy production in a food chain.
Each bar represents the amount of energy (measured in joules, J) in each trophic level.
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28. Energy Pyramids
Orange 10,000 J
Oriole 1,000 J
Hawk 100 J
Bobcat 10 J
As so much energy is lost at each trophic level, food chains usually consist of no more than four or five trophic levels.
The most energy is found at the first trophic level, which contains all the producers in the chain. This is therefore the largest section of the pyramid.
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29. Energy Pyramids
Orange 10,000 J
Oriole 1,000 J
Hawk 100 J
Bobcat 10 J
On the way up the food chain, the amount of energy at each trophic level decreases. The top predator in the food chain contains the least energy.
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30. The Recycling of Energy
When a plant or animal dies, it becomes dead organic matter.
Dead organic matter (biomass) contains stored energy and nutrients of the living organism. This is returned to the food chain through the process of decomposition or decay.
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31. The Recycling of Energy
Bacteria and fungi (together known as decomposers) break down the tissues of the dead organism, releasing stored energy and nutrients back into the soil.
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32. Composting
These released nutrients, for example, as nitrates and phosphates, can then be re-used by plants at the beginning of another food chain.
Nutrients
Decaying Matter
Decomposers release nutrients into the soil
Death and decay
Plants take up the nutrients in the soil
Plants take in the nutrients through their roots and use them for growth, repair and in the making of food.
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33. Composting
Gardeners can make use of the decay process by encouraging the process in controlled conditions.
Nutrients
Decaying Matter
Decomposers release nutrients into the soil
Death and decay
Plants take up the nutrients in the soil
This process is called composting.
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34. Composting
In a small area, as a heap or in a container, dead organic matter is gathered and left to decompose.
The process of decay requires oxygen, and moisture. Gardeners often carefully control these things, by turning the materials and adding measured amounts of water.
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35. Composting
After a year or more, the contents become a dark, sweet smelling material that is very rich in nutrients.
This nutrient-rich material is then added to soils as a fertilizer.
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36. Question 6
Which of the following groups of organisms break down dead matter and release nutrients into the soil?
A) Consumers
B) Decomposers
C) Herbivores
D) Producers
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37. Question 6
Which of the following groups of organisms break down dead matter and release nutrients into the soil?
A) Consumers
B) Decomposers
C) Herbivores
D) Producers
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38. Summary In this presentation you have seen:
how energy enters and flows through ecosystems
how energy is recycled between food chains
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