1. Chemical Cycles

2. What is a cycle? cy·cle n. A periodically repeated sequence of events. cy·cle n. A periodically repeated sequence of events.

3. Why are chemical cycles necessary for life to exist? 1. Nutrients such as carbon, oxygen, and nitrogen are needed for organisms to live and grow. 2. These elements, along with all others, are not constantly replenished from an outside source. Remember that the energy cycle has a constant input of energy from the sun. Remember that the energy cycle has a constant input of energy from the sun.

4. The three cycles 1. The carbon cycle—the movement of carbon through the environment. 2. The nitrogen cycle—the pathway by which nitrogen moves through the environment. 3. The water cycle—the continual movement of water from the Earth’s surface to the atmosphere and back to the surface again.

5. The Carbon Cycle Carbon is the building block atom of all organic compounds. Carbon is the building block atom of all organic compounds. Carbon-based compounds move through air or water, through living things, and back to air or water again. Carbon-based compounds move through air or water, through living things, and back to air or water again. The driving forces behind the carbon cycle are: The driving forces behind the carbon cycle are: 1. photosynthesis 2. and cellular respiration

6. Photosynthesis CO 2 + H 2 0 + energy → C 6 H 12 0 6 + O 2 The process by which autotrophs convert sunlight into a useable form of energy (glucose). The process by which autotrophs convert sunlight into a useable form of energy (glucose). Occurs in the chloroplasts of plant cells (an organelle). Occurs in the chloroplasts of plant cells (an organelle).

7. Cellular Respiration C 6 H 12 O 6 + O 2 → CO 2 + H 2 0 + energy res·pi·ra·tion n. The act or process of inhaling and exhaling; breathing. res·pi·ra·tion n. The act or process of inhaling and exhaling; breathing. Cellular respiration is the process by which glucose is broken down to release energy. Cellular respiration is the process by which glucose is broken down to release energy. Occurs in in the mitochondria of ALL cells (another organelle). Occurs in in the mitochondria of ALL cells (another organelle).

8. Photosynthesis—the construction of glucose to store energy. CO 2 + H 2 0 + energy → C 6 H 12 0 6 + O 2 Photosynthesis—the construction of glucose to store energy. CO 2 + H 2 0 + energy → C 6 H 12 0 6 + O 2 Cellular Respiration—the breakage of glucose to release energy Cellular Respiration—the breakage of glucose to release energy C 6 H 12 O 6 + O 2 → CO 2 + H 2 0 + energy C 6 H 12 O 6 + O 2 → CO 2 + H 2 0 + energy

10. Humans and the carbon cycle Humans have begun to interfere with the carbon cycle by: Humans have begun to interfere with the carbon cycle by: 1. Cutting down forests 2. Burning fossil fuels (energy-rich organic materials that are formed from geological processes: coal, gasoline, oil, etc.)

11. The Nitrogen Cycle Nitrogen is needed to make amino acids, proteins, and other necessary substances. Nitrogen is needed to make amino acids, proteins, and other necessary substances. It moves through atmosphere and soil, through living things, and back to the atmosphere and soil again. It moves through atmosphere and soil, through living things, and back to the atmosphere and soil again.

12. Composition of the atmosphere Nitrogen makes up almost 80% of the air you breathe every day! Nitrogen makes up almost 80% of the air you breathe every day! The rest is made up of O 2, Ar, CO 2, and other traces of gases. The rest is made up of O 2, Ar, CO 2, and other traces of gases.

13. Two important N 2 -cycle processes 1. Nitrogen fixation— bacteria in the soil or the root nodules of legumes convert N 2 that is present in the atmosphere to ammonium ions that plants can take up and use.

14. Two important N 2 -cycle processes 2. Denitrification— another group of bacteria convert some of the ammonium and nitrates in the soil into free nitrogen gas.

16. Humans and the N 2 cycle Nitrogen compounds dissolve easily in water, so are lost with erosion (the result of deforestation). Nitrogen compounds dissolve easily in water, so are lost with erosion (the result of deforestation). Crop plants like corn and cotton absorb nitrogen excessively— causing farmers to use nitrogen fertilizers, which are very expensive to make (and pollute the environment during the process). Crop plants like corn and cotton absorb nitrogen excessively— causing farmers to use nitrogen fertilizers, which are very expensive to make (and pollute the environment during the process).

17. The Water Cycle Water is necessary for all life processes. Water is necessary for all life processes. Water cycles from the atmosphere, to the Earth, through organisms, and back to the atmosphere. Water cycles from the atmosphere, to the Earth, through organisms, and back to the atmosphere. The two driving forces of the water cycle are: The two driving forces of the water cycle are: 1. Solar energy 2. Gravity

18. Definitions (write down what you don’t know) Evaporation—liquid changing to a gas. Evaporation—liquid changing to a gas. Transpiration—evaporation from the leaves of trees. Transpiration—evaporation from the leaves of trees. Condensation—gas changing to a liquid. Condensation—gas changing to a liquid. Precipitation—rain, snow, sleet, and hail. Precipitation—rain, snow, sleet, and hail.

19. The steps of the water cycle 1. Water evaporates or transpires and rises in the atmosphere (this requires energy from the sun). 2. As it rises, it cools and condenses to form clouds. 3. The droplets of the clouds eventually get big enough and fall back to the surface of Earth by gravity. 4. The water is absorbed and collected in lakes, streams, ponds, and oceans—the cycle begins all over again.

21. Humans and the water cycle Chemicals, sewage, trash, and toxic wastes find their way into rivers, ponds, and lakes all over the world. Chemicals, sewage, trash, and toxic wastes find their way into rivers, ponds, and lakes all over the world. These eventually travel underground and contaminate our groundwater—the source of all our fresh drinking water. These eventually travel underground and contaminate our groundwater—the source of all our fresh drinking water. Deforestation also prevents absorption of rainfall making land susceptible to flooding and erosion. Deforestation also prevents absorption of rainfall making land susceptible to flooding and erosion.

22. To Review Nutrients such as carbon, oxygen, and nitrogen are needed for organisms to live and grow. Nutrients such as carbon, oxygen, and nitrogen are needed for organisms to live and grow. These elements, along with all others, are not constantly replenished from an outside source. These elements, along with all others, are not constantly replenished from an outside source. 1. The carbon cycle—the movement of carbon through the environment. 2. The nitrogen cycle—the pathway by which nitrogen moves through the environment. 3. The water cycle—the continual movement of water from the Earth’s surface to the atmosphere and back to the surface again.