Biology Unit 10: Energy Flows in Ecosystems

source

Unit 10 Energy Flows in Ecosystems

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.

As you go up a trophic level, energy is lost. For example, we have this chain:

mahogany tree → caterpillar → song bird → hawk

The mahogany tree gets the biggest amount of energy from the Sun. When the chain reaches the hawk, the hawk gets a very small amount of energy from the song bird. This is because energy is lost throughout the chain due to heat loss. Only about 10% of energy gets passed on to the next species in the chain. 

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.

As said above, only 10% of energy gets passed on from each species in the chain. If the chain were to continue, eventually there would be no energy to pass on. This is why food chains have a limit of around five trophic levels.

6. Describe the carbon cycle.

The carbon cycle is the cycle of which carbon travels around the Earth's atmosphere.

source

7. Discuss the effects of the combustion of fossil fuels and the cutting down of forests on the oxygen and carbon dioxide concentrations in the atmosphere.

Combustion of fuels results in carbon dioxide and nitrous oxides being released into the atmosphere. These contribute to overall global warming. Deforestation increases the amount of carbon dioxide in the atmosphere; this is because there are no more trees to use carbon dioxide for photosynthesis.