Cycles in Nature 13.2

A. Water Cycle Evaporation – takes place when water changes into water vapor, which is a gas, and enters the atmosphere

B. Types of Evaporation water evaporates from the surface of lakes, streams, puddles and oceans water vapor enters the atmosphere from plant leaves in a process known as transpiration animals release water vapor into the air when they exhale water also returns to the environment from animal wastes

C. Condensation Condensation – the process of changing from a gas to a liquid Water vapor that has been released into the atmosphere comes in contact with colder air Temperature of the water vapor drops Water will eventually cool enough to change back into liquid water (which is called condensation) Example: Cold drink sweating like a soda

Water vapor condenses on particles of dust in the air, forming tiny droplets At first, the droplets clump together to form a cloud When they become large and heavy enough, they fall to the ground as rain or other precipitation

D. Water Use The amount of water people take from reservoirs, rivers, and lakes for use in households, businesses, agriculture, and power production reduce the amount of water that evaporates into the atmosphere Why would this be a concern? Because the less water that there is to evaporate, the less water there is to create rain and come back to the earth. It also takes away water for plants and animals in nature.

E. Nitrogen Cycle Nitrogen is a necessary ingredient of proteins Proteins are required for the life processes that take place in the cells of all organisms Nitrogen is also an important part of the DNA in organisms

Nitrogen is the most available gas in the atmosphere (78% of the air), but most organisms cannot use nitrogen directly from the air For plants, nitrogen must be combined with other elements to form nitrogen compounds Nitrogen fixation – a process in which some types of soil bacteria can form the nitrogen compounds that plants need Plants absorb the nitrogen compound through their roots

Animals obtain nitrogen they need by eating plants or other animals When dead organisms decay, the nitrogen in their bodies returns to the soil or to the atmosphere Nitrogen cycle – the transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere

F. Soil Nitrogen The nitrogen cycle can be affected by humans When farmers grow crops, the plants take in the nitrogen from the ground, but the plants don’t decay in the same place so the nitrogen is moved to a different location If the nitrogen compounds are not replaced, the soil could become infertile

Fertilizers can be used to replace soil nitrogen in crop fields, lawns, and gardens Compost and animal manure also contain nitrogen compounds that plants can use and be added to improve fertility

Farmers will also grow nitrogen-fixing crops such as peas, clover, and beans like soybeans These plants have nitrogen-fixing bacteria that grow on their roots The nitrogen compounds are supplied to the plants and the soil

G. The Carbon Cycle Carbon cycle – describes how carbon molecules move between the living and nonliving world Carbon atoms are found in the molecules that make up living organisms Carbon is an important part of soil humus and it’s found in the atmosphere as carbon dioxide gas

Carbon cycle starts when producers remove carbon dioxide from the air during photosynthesis They use carbon dioxide, water, and sunlight to produce energy rich sugar molecules and energy is released from these molecules during respiration

Respiration uses oxygen and releases carbon dioxide Photosynthesis uses carbon dioxide and releases oxygen These two processes help recycle carbon on Earth

H. Harmful Carbon Dioxide Release Human activities also release carbon dioxide into the atmosphere Using fossil fuels as gasoline, coal, and heating oil These fuels are made up energy-rich, carbon-based molecules When these are burned, carbon dioxide is released into the atmosphere as a waste product

Wood is used for building or burning and this wood comes from trees that can no longer remove carbon dioxide from the atmosphere This causes an increase of carbon dioxide not being removed as quickly as it is being created. More heat is trapped in the atmosphere, helping to cause Global Warming

Review 1. Why is evaporation an important process? 2. How do animals release water vapor? 3. What is an unusual way water vapor is released into the atmosphere? 4. How does the process of condensation work?

5. How is a cloud formed? 6. What are ways that people take Earth’s water? 7. Why do people need to be careful how quickly and how much water is used on Earth? 8. What is a necessary ingredient for proteins? 9. Why are proteins important?

10. How do plants get the necessary nitrogen compound to survive. 11 10. How do plants get the necessary nitrogen compound to survive? 11. How is nitrogen used and returned back to the earth? 12. How can the nitrogen cycle be affected by humans? 13. What would happen if nitrogen compounds are not returned back to the earth?

14. What are the 3 ways that humans can replace nitrogen compounds back to Earth? 15. How can planting certain crops help replace nitrogen compounds to the earth? 16. Where are carbon atoms found? 17. How does the carbon cycle start? 18. What two processes help replace carbon on Earth?

19. How are humans causing Global Warming. 20 19. How are humans causing Global Warming? 20. Why is Global Warming dangerous?