1. Science 7 - Unit A: Interactions and Ecosystems
Topic 5: Cycles in the Environment

2. Cycles in the Environment
There are numerous cycles in the environment that recycle materials, nutrients, and a small part of the energy of an ecosystem.
Remember that almost all of the energy captured by producers is lost keeping the different organisms alive.

3. The Carbon Cycle
All organisms contain carbon. Fossil fuels, which are the remains of dead plant and animal matter are also made of carbon.
When organisms die, and their remains are pressurized for a long time, fossil fuels, such as oil are created. These fuels all contain carbon.
Carbon also exists as carbon dioxide in an ecosystem. Carbon dioxide is necessary for plants to undergo photosynthesis.

4. The Carbon Cycle

5. The Water Cycle
Water is necessary for life. The human body itself is 60% water.
Water is necessary for all of life’s functions: eating, reproducing, eliminating wastes, etc.
The water cycle is the continuous movement of water through an ecosystem. It involves four main processes:
1. Evaporation
2. Transpiration
3. Condensation
4. Precipitation

7. Pollution
Any chemical that is added too quickly or too heavily into an ecosystem so that it cannot be recycled is a pollutant.
Pollutants can be everyday chemicals such as carbon dioxide (a greenhouse gas).
Other pollutants include nitrogen and sulfur compounds which, when mixing with water vapour form acid rain.

8. Acid Rain
Has a pH of 5.6 or less. (5.6 is about as acidic as a pop drink).
Can destroy lakes and other wetland ecosystems by making the groundwater too acidic for plants and animal species (fish).
Acid rain can also damage buildings and other structures.

9. How do pollutants move?
Harmful chemicals such as PCBs, CFCs, and heavy metals take a long time to break down. If they leak or are released into the ecosystem they will be there for generations.
Problems such as holes in the ozone layer, mercury poisoning, and the death of peregrine falcons are the result of pollutants.

10. Bioaccumulation
Bioaccumulation is the gradual build-up of pollutants in organisms as they travel up a food web.
Eg. A small fish eats a shrimp with one unit of mercury inside it. However the small fish needs to eat two shrimp a day to survive. Now it has two units of mercury in it a day.
A big fish eats two small fish a day to survive. This fish has now four units of mercury pollution inside its body each day.
A bear eats two big fish a day to survive. Each day, it adds 8 units of mercury to its body.