1. Cycles in Nature
7th Grade Science

2. Think!
What is a cycle? What are some cycles you know about in the world we live in?

3. What is a cycle?
A single complete execution or a periodically repeated phenomenon.
What does that mean?
Single – it happens one time
Complete – it is the entirety of the steps involved in the cycle (Example: egg – larva – pupa – adult)
Periodically repeated – it goes on over and over again

4. Examples of Cycles
Life Cycle of a Butterfly

5. Discuss
Imagine a world where your cycle did not take place. What would be the result?

6. What is matter?
Matter is anything that has mass and takes up space

7. What is energy The capacity or power to do work
There are different forms of energy. Examples include: electrical, mechanical, chemical, thermal, or nuclear
Energy can be transferred or transformed. It also can be stored in different forms.

8. Example
During cellular respiration, energy stored as chemical energy in glucose is converted into ATP, a type of energy that is usable by the organism
This is then used by the organism for growth or life functions
Cellular respiration occurs in all cells. That means it occurs in plants and animals but also occurs in all cells (not just digestive cells) of a multicellular organism

9. Water Cycle
the cycle of processes by which water circulates between the earth's oceans, atmosphere, and land, involving precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation and transpiration
Why is this considered a cycle?
Is this the cycling of energy, matter, or both in nature?

11. Nitrogen Cycle
Interconverted – to convert into each other
the series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms, including nitrogen fixation and decomposition.
One of the most important parts to understand about the nitrogen cycle is that despite the fact that nitrogen is the most abundant gas in our atmosphere (making up 78% of the air we breathe), organisms do not get nitrogen by breathing it in. This is because of the strong bond between the two nitrogen atoms. Only lightning and nitrogen fixing bacteria are strong enough to break these bonds. Plants therefore get nitrogen (needed for chlorophyll) from compounds made by the nitrogen-fixing bacteria in the soil. Animals get nitrogen by eating plants. We need nitrogen because it is an important part of DNA and other amino acids used in our bodies to form hair, muscles, skin, and other tissues.
Why is this considered a cycle?
Is this the cycling of energy, matter, or both in nature?

13. Carbon Cycle
the series of processes by which carbon compounds are interconverted in the environment, chiefly involving the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms, and the burning of fossil fuels.
Carbon is important because it is a major part of organic compounds including carbohydrates (like glucose), lipids, nucleic acids, and proteins. These are used in our bodies to obtain energy and also to make up different parts of the body.
Why is this considered a cycle?
Is this the cycling of energy, matter, or both in nature?

15. So what about food?
With your group, develop a model to show how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through the organism. You may use materials from this room or that you have at home. We will share and critique these models next class, so be sure you are ready.

16. So what is the big deal when it comes to these cycles?
Without the continuation of these cycles life would not be possible.
Matter and Energy never disappears, it is just transformed or rearranged into some other form of matter or energy.
Matter and Energy can be (and often are) cycled together. How can you tell the difference?