1. Earth Cycles
Science

2. What is a cycle? A cycle is a series of repeating events. Examples?
The most important cycles for living things involve water, carbon and nitrogen.
In all of these cycles, matter moves continuously through the atmosphere, the land, and living things.

3. The Water Cycle
Movement of water through the atmosphere, the ground, and bodies of water, and living things is called the water cycle.

4. Evaporation
Evaporation is the change from a liquid (such as water) to a gas.
In the water cycle, evaporation occurs when the sun’s energy warms the water in oceans, lakes and soil.
Question: Where does the water vapor go when it is formed?

5. Transpiration
Transpiration is the process by which living things release water vapor into the atmosphere.
Plants and algae release most of the water vapor.

6. Quick Check
What are two processes that allow water to move into the atmosphere?

7. Condensation
Who has seen a “sweating” glass of ice water before?
Condensation is the process by which water vapor changes from a gas to a liquid.
This change occurs when the water vapor cools, which creates the liquid again.
When have we seen this happen?

8. Precipitation
Precipitation includes rain, snow, sleet, & hail.
-water moves from the atmosphere to the land and the ocean as precipitation
- this precipitation seeps into the ground, where it is stored in underground caverns or in porous rock
-groundwater supplies water to soil, streams, rivers, and oceans

9. Water Cycle
Condensation

10. Quick Check
Once the vapor goes up into the atmos-phere, how does it come back down?

11. Carbon Cycle
Another cycle that is very important to all organisms on Earth is the carbon cycle.
Since all living things are made up of molecules that contain carbon, this cycle is very important.
Carbon cycle is the movement of carbon from the nonliving environment into living things and back.

12. Photosynthesis
Photosynthesis is the process by which plants use carbon dioxide from the air to make sugars.
Most animals get the carbon they need by eating plants.
(Carbon bonds store energy allowing living organisms to move, eat, sleep, breath and repair – so important!)

13. Photosynthesis Equation
H2O + CO O2 + C6H12O6
H2O - water
CO2 - carbon dioxide
- from the sun
- with green chlorophyll
O2 - oxygen
C6H12O6 - glucose sugar
LIGHT ENERGY
LIGHT ENERGY

14. Photosynthesis
Photosynthesis usually occurs in the leaves of plants, specifically in the chloroplasts of each cell.
Do root cells have chloroplasts?
Only plants, algae, some protists, and some bacteria are photosynthetic producers.
Animals, fungi, and other protists and bacteria are consumers. They are not photosynthetic.

15. Cell Respiration Respiration
Respiration returns the carbon from plants and animals to the atmosphere.

16. Cell Respiration Equation
O2 + C6H12O6
ATP ENERGY
H2O + CO2 +
º Cell respiration occurs in the cells of all living
organisms.
º This process keeps it alive by creating energy in a
form that the cells can use.
º Without this ATP energy, the cell cannot perform
any of its vital functions (make/acquire food, break
it down, make DNA, reproduce, etc.).

17. Decomposition
Decomposition is the breakdown of dead organisms and organic wastes, which releases carbon dioxide.
Ex. When fungi and certain bacteria decompose organic matter, they return carbon to the soil and air.

18. Combustion
Carbon in coal, oil, and natural gas is returned to the atmosphere as carbon dioxide when these fuels are burned.

19. The Carbon Cycle

21. Sources of Carbon from
Human Activity:
• Burning wood or forests
• Cars, trucks, planes
• Burning fossil fuels such
as coal, oil and natural
gas to produce heat and
energy for our homes and
businesses
Natural Sources
of Carbon:
• Death of plants and
animals
• Animal waste
• Atmospheric CO2
• Weathering
• Methane gas from cows
(and other ruminants)
• Aerobic respiration from
terrestrial and aquatic life

22. Nitrogen Cycle
- movement of nitrogen from the nonliving environment into living things and back again

23. Nitrogen Cycle
About 78% of the Earth’s atmosphere is made up of nitrogen gas (N2).
All organisms need nitrogen to build protein and DNA , but cannot use N2 as it is.
Nitrogen fixation- nitrogen is changed into a usable form by certain bacteria in plant roots and soil (usable forms = ammonia, nitrates, nitrites)
Then, as animals eat plants they get the usable nitrogen.

24. Nitrogen Cycle - key points
Some bacteria help get usable nitrogen ready for animals.
Other types of bacteria help return the nitrogen to the atmosphere.
These bacteria break down dead organisms and animal wastes.

25. Nitrogen cycle

26. Pollution
Pollution is the presence of dangerous levels of substance in the environment.
The pollutants might be a solid, chemical, gas, or even energy.
When they enter the cycles, they disrupt the normal cycles.

27. Pollution Over time human activities have altered the cycles. How?
Pollution from our busy lives has affected our soil, water, and air quality.
We are using resources faster than they can be replaced.

28. Resource Depletion
Humans cause environmental problems by using up or depleting natural resources.
renewable resources can be used over and over again or has an unlimited supply
nonrenewable resources cannot be replaced (or can be replaced, but over thousands or millions of years)

29. Check for Understanding
What would happen to the water cycle, carbon cycle, and nitrogen cycle if most of the land on Earth were paved?
Predict what would happen if scientists would develop a crop with more nitrogen fixing bacteria in their roots.

30. Modifications of Earth Cycles
What are some things that alter the cycles?
Do these changes alter just one cycle or can they affect all of the cycles?

31. Quick Check What is the major reason that the cycles are altered?
Give some examples on how humans have changed specifically the nitrogen cycle?

32. Why is resource depletion bad for the Earth’s cycles?
If soil erosion continues, then the cycles will not continue the same.
-water washes away soil, what are the causes?
If air continues to be polluted, the cycles will not convert the air as before and C and N levels released will not be the same.

33. Why is resource depletion bad for the Earth’s cycles?
Habitat destruction is another way humans have modified air quality, soil, and water on Earth.
Our pollution is affecting where organisms live.
Forests and wetlands have been altered and affected by our pollution.
These changes have really affected the cycles of the Earth and will continue to alter the cycles.

34. Human Modification of Cycles can affect the balance of:
Producer-a photosynthetic organism
Primary Consumer -an animal that eats grass and other producers in a food chain; an herbivore
Secondary Consumer -an animal that feeds on smaller herbivores
Tertiary Consumer -an animal that feeds on secondary consumers
Decomposer -an organism, often a bacterium or fungus, that feeds on and breaks down dead plant or animal matter, thus making organic nutrients available to the ecosystem
An animal that feeds on secondary consumers in a food chain

35. Thought Questions -relate all answers to cycles-
What will happen if trees are not being replaced when used?
What will happen if soil erosion occurs?
What will happen to the nitrogen cycle if there are fewer healthy plants?
What will happen if nitrogen fixing bacteria are not present?

36. Questions for Assessment
Describe how human activities have modified soil and water.

37. Describe how human activities have modified soil and water
Predict results of modifying the Earth’s cycles; water, carbon & nitrogen and show that modification may disrupt the delicate balance of producers, consumers, and decomposers.
Modifications:
Volcanic eruption
Power plant
(burning fossil fuels)
Fertilizer run-off

38. What if:
a volcano erupted causing events of catastrophic proportions; draw and explain how this would affect the Earth’s cycles