1. Topic 5: Cycles in the Environment
Grade 7 Unit 1
Topic 5: Cycles in the Environment

2. An Overview The Earth is made up of a finite amount of material.
In order for species to survive through the generations material needs to be recycled through the ecosystem.
The recycling of materials is referred to as cycles.

3. The Carbon Cycle The carbon cycle is necessary for all forms of life.
Plants use carbon dioxide in the air to make their own food.
Animals eat plants and other consumers therefore receive their carbon from what they eat and release carbon gas back into the air.
When plants and animals die the decomposers recycle the carbon so other organisms can reuse it.

4. The Carbon Cycle cont.
Carbon is constantly moving in an ecosystem that is why we call it the carbon cycle.

5. The Carbon Cycle cont.
Activity – Read and answer the « Looking Ahead » on page 49. Use the following information to help you with your answer.
Over time and under high pressures, the fossils of dead organisms formed fossil fuels. These fuels contain the same carbon that was in the original organisms.

6. The Water Cycle
Water is vital to life processes such as transporting food, in useable form, to the cells and to carrying wastes from those cells.

7. The Water Cycle cont.
The water cycle is the continuous circulation of water in an ecosystem.
Only 2% of the water is in a stable state (ice, ground water and water is inside organisms). So 98% of the Earth's water is continuously circulated between the Earth and the atmosphere.

8. The Water Cycle cont. This cycle comprises: Evaporation
Process by which a liquid becomes a gas/vapour.
Earth  atmosphere

9. The Water Cycle cont. Transpiration
Process by which water that is taken in through plant’s roots evaporates from the leaves, stem and flowers of a plant.
Earth  atmosphere

10. The Water Cycle cont. Condensation
Process by which water vapour turns into a liquid.
creates clouds, fog or dew

11. The Water Cycle cont. Precipitation
Process in which liquid water forms from condensation occurring inside clouds and then falls as rain, sleek, snow or hail
Atmosphere  Earth

12. The Water Cycle cont. The ground water: is the water in the soil
people can reach ground water by digging wells.

13. The Water Cycle cont. Water runoff:
water that runs off the ground into lakes and rivers.

14. Water cycle cont…
?Read « Did you know » on page 51 and fill in the blanks in the following diagram?

15. Water cycle cont…
The fact that the water particles that your great-great-great-great grandparents saw still exist it is not surprising because the material is still recycled.

16. Pollution in the Environment
Matter, energy, carbon, and water all constantly cycle through the ecosystem, but other more harmful substances can also cycle through:
Pollutants are substances that cause pollution. Many substances become pollutants when they are present in concentrations too high for the environment to absorb without negative effect.
Pollution is a degradation of the environment by introducing air, water or soil material that is not naturally present in the area.
It causes a disturbance of the ecosystem, the consequences can go to the migration or extinction of organisms unable to adapt to the changes.

17. Pollution in the Environment
Examples of the effects of pollutants:
Acid Rain:
Water with a pH below 5.6.
Occurs when waste gases (containing sulphur and nitrogen) released into the atmosphere by industries and automobiles are mixed with water vapour.

18. Pollution in the Environment

19. Pollution in the Environment cont.
The pH scale
Measures the acidity of liquids and ranges from 0 (very acidic) to 14 (alkaline/basic)
The pH scale measures the acidity of liquids, and ranges from 0 (very acidic) to 12 (not acidic)

20. The Movement of Pollution
There are many different pollutants moving through the environment including:
(a) PCBs polychlorinated biphenyls
• Compounds containing chlorine
• Used in many industrial processes, paints, packaging materials
• They were thrown into landfills and entered the air, water and ground. They breakdown very slowly so they remain in the ground and ground for years therefore causing harm to organisms.

21. The Movement of Pollution cont.
(b) Mercury
atomic element (liquid at room temperature)
in the past, the industry poured tons of mercury in landfills. The soil became infiltrated with mercury which dissolved into the ground water
It accumulates in the tissues of organisms and enters the food chain
Mercury attacks the nervous system
This bird has been damaged by mercury poisoning.

22. The Movement of Pollution cont.
(c) DDT (pesticides)
Dichloro-diphenyltrichloroéthane
• pesticide used in the 1940’s-1960’s
• Takes time to degrade
• Enters into the food chain
• Traces found in humans
Dr. Rachel Carson’s observations
in ecology led to studies that
showed DDT caused the death of
thousands of young eagles and
hawks.

23. ?Read « Did You Know » on page 53 and ?answer the following question
Why is DDT illegal in certain countries?

24. Bioaccumulation
The pollutants of a food web move from one level to another. Bioaccumulation is the movement of pollutants through levels of a food chain so that the greater quantities are retained with movement up the food chain.

26. Bioaccumulation 1
Mercury enters the water after leaking out of a waste-disposal site and settles on the bottom of the lake.

27. Bioaccumulation cont. 2
The mercury enters the systems of micro-organisms living in the sediment and the algae in the water.

28. Bioaccumulation cont. 3
Baby fish eat the micro-organisms and the algae, and the mercury accumulates in their systems.

29. Bioaccumulation cont. 4
Small, carnivorous fish eat the baby fish, and absorb the mercury contained in all of the baby fish. The mercury stays dissolved in the fatty tissue.

30. Bioaccumulation cont. 5
Larger, carnivorous fish eat the smaller fish, and absorb the mercury contained in all of the smaller fish. The mercury, again, stays dissolved in the fatty tissue.

31. Bioaccumulation cont. 6
The large fish are caught and eaten by a human. The human eats several fish over time and accumulates the mercury that was in all the fish eaten.