Biology Unit 10: Energy Flows in Ecosystems

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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.

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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. 

Biology Unit 11: Human Influences on the Ecosystem

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Unit 11 Human Influences on the Ecosystem

1. List the undesirable effects of deforestation (to include extinction, loss of soil, flooding, carbon dioxide build up).

• Trees serve has habitats for animals; if they are cut down animals lose their homes and become more vulnerable to predators. The species will die out because they don't have a place to live

• Without trees, land is vulnerable to weather conditions that cause erosion

• Flooding will become easier because the land has no barriers that stop the water

• Trees use carbon dioxide in photosynthesis, and without trees the carbon dioxide levels in the atmosphere will rise

2. Describe the undesirable effects of overuse of fertilisers (to include eutrophication of lakes and rivers).

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3. Describe the undesirable effects of pollution to include: 

• water pollution by sewage and chemical waste, 

• air pollution by greenhouse gases (carbon dioxide and methane) contributing to global warming.

If chemical waste and rubbish flow into our seas, this basically makes the water unclean and makes it difficult for aquatic life to survive.

Carbon dioxide and methane are both greenhouse gases; greenhouse gases are the gases that absorb heat and reflect it back into the atmosphere, causing the world temperature to increase. This is bad for the environment as heat will cause ice at the Poles to melt, raising average sea levels.

4. Discuss the causes and effects on the environment of acid rain, and the measures that might be taken to reduce its incidence.

When sulphur dioxide and nitrogen oxides are released into the atmosphere, they mix with oxygen, water, and other chemicals. This causes acid rain. 

To reduce buildup that leads to acid rain, the burning of fossil fuels should be reduced. This is because combusting fossil fuels release both sulphur dioxide and nitric oxides. 

5. Explain how increases in greenhouse gases (carbon dioxide and methane) are thought to cause global warming.

This is similar to second point of point 3.

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6. Describe the need for conservation of: 

• species and their habitats, 

• natural resources (limited to water and non-renewable materials including fossil fuels).

Species need to me conserved because all specie are part of the food chain. If the food chain is disrupted, all species of the food chain will be affected, including humans. Their habitats must also be conserved to ensure they are able to survive.

Natural resources must be conserved because the Earth has only a limited amount. If all resources were to be used up, there would be none left for future generations. While fossil fuels can be produced again, it would take millions of years, and humanity doesn't have that much time to wait!