NAME____________________
CHAPTER 3- ENERGY AND ECOSYSTEMS
STUDY GUIDE
DEFINITIONS:
photosynthesis- the process which by plants make food, using energy from the sun
producer- an organism that makes its own food
consumer- an animal that eats plants or other animals
decomposer-an organism that breaks down the remains of dead plants and animals.
herbivore- an animal that eats only producers
carnivore- an animal that eats other consumers (animals)
omnivore- an animal that eats producers and consumers (plants and animals)
food chain- the transfer of food energy between organisms in an ecosystem.
food web- a diagram that shows the relationship between many food chains
energy pyramid- a diagram that shows how much food energy is passed from each level in a food
chain to the next.
SCIENCE CONCEPTS:
1. What is the source of all energy on Earth?
The sun. Plants use this energy to perform photosynthesis.
2. What percentage of energy is passed on to the organisms at each level of an energy pyramid?
10%
3. Be able to explain the stages in the nitrogen cycle. (Draw a diagram below)
Nitrogen is fixed by bacteria in the soil or by lightning.
Plants use the nitrogen to grow.
Animals eat the plants and get the nitrogen.
Animals and plants die, they decay, and the nitrogen is returned to the soil and the
cycle starts again.
4. What does a plant use to perform photosynthesis (what does the plant need)? What does the
plant give off as part of this process?
Plants need CO2, water, sunlight, and chlorophyll to perform photosynthesis.
Plants produce sugars (for the plant) and give off oxygen as a byproduct.
5. Draw a simple food chain that includes a producer, a first-level consumer, a second-level
consumer, and a third level consumer. Be sure the arrows show the flow of energy.
grass------- mouse-------fox--------hawk
6. Explain what happens to animals in a food web if one of the species of animals decreases in
number.
The animals that eat that animal will decrease because they will not have enough
food. The organisms that the first animal eats will increase because nothing will
be eating them.
7. Where do decomposers fit into the food chain? What is their job? What are some examples of
decomposers?
Decomposers are at the end of the food chain. They connect the end back to the
beginning because they put nutrients back into the soil that the producers use to grow.
Examples of decomposers include mushrooms, fungi, and bacteria.