2 Water is ESSENTIAL for life. Water never leaves the Earth Water is ESSENTIAL for life. Water never leaves the Earth. It is constantly being cycled through the atmosphere, ocean, and land. This process, known as the water cycle, is driven by energy from the sun. The water cycle is crucial to the existence of life on our planet.
5 During part of the water cycle, the sun heats up liquid water and changes it to a gas (water vapor) by the process of evaporation. Water that evaporates from Earth’s oceans, lakes, rivers, and moist soil rises up into the atmosphere. People release water in their wastes and water vapor when they exhale.
6 The process of evaporation from plants is called transpiration The process of evaporation from plants is called transpiration. (In other words, it’s like plants sweating.)
7 As water vapor rises higher in the atmosphere, it starts to cool and become a liquid again. This process is called condensation. When a large amount of water vapor condenses, it results in the formation of clouds.
8 When the water in the clouds gets too heavy, the water falls back to the earth. This is called precipitation. Precipitation can be rain, snow, sleet, or hail. Precipitation may fall into oceans, lakes, or rivers.
9 When rain falls on the land, some of the water is absorbed into the ground forming pockets of water called groundwater. Most groundwater eventually returns to the ocean. Other precipitation runs directly into streams or rivers. Water that collects in rivers, streams, and oceans is called runoff.
10 What Is Carbon?Carbon is one of the most abundant elements on Earth, and is known as “the basic building block of life”.The basis of life on earth – a continual supply of carbon is essential for all living organisms.The total amount of carbon on Earth, whether we are able to measure it accurately or not, always remains the same (although the carbon regularly changes its form).Found in rocks, oceans, atmosphere, plants, living organisms (found in bones and proteins that build muscles), etc…
11 Carbon CycleThe same carbon atoms are used repeatedly on earth (because new matter can never be created – it is essential that living things be able to reuse the existing matter again and again). The carbon atoms cycle between the earth and the atmosphere.
12 Plants Use Carbon Dioxide Plants pull carbon dioxide from the atmosphere and use it to make food (carbon-containing molecules such as sugars and starches) –—this happens during photosynthesis.The carbon becomes part of the plant (stored food).
13 Animals Eat PlantsWhen consumers eat plants, they take in the carbon and some of it becomes part of their own bodies.
14 Carbon Slowly Returns to the Atmosphere When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere.Some are not decomposed fully and end up in deposits underground (oil, coal, etc.).Carbon in rocks and underground deposits is released very slowly into the atmosphere.This process takes many years. The cycle REPEATS over and over……
15 Carbon Cycle Diagram Carbon in Atmosphere Plants use carbon to make foodAnimals eat plants and take in carbonPlants and animals dieDecomposers break down dead things, releasing carbon to atmosphere andsoilBodies not decomposed — after many years, become part of oil or coal depositsFossil fuels are burned; carbon is returned to atmosphereCarbon slowly released from these substances returns to atmosphere
17 Carbon in the Oceans Additional carbon is stored in the ocean. Many animals pull carbon from water to use in shells, etc.Animals die and carbon substances are deposited at the bottom of the ocean.Oceans contain earth’s largest store of carbon.
18 The Oxygen Cycle Oxygen also cycles through ecosystems. Producers release oxygen as a result of photosynthesis. Most organisms take in oxygen from the air or water and use it to carry out their life processes.Producers can also use oxygen for respiration. In respiration, plants take in oxygen to help break down the sugars into energy that is then used to repair and replace tissues. However – plants release much more oxygen during photosynthesis than they consume during respiration.
20 The Nitrogen CycleNitrogen is also a necessary building block for living things.Since the air is 78% nitrogen gas, it seems that it would be easy for living things to obtain nitrogen. However, most organisms cannot use nitrogen gas.Nitrogen gas is called “free” nitrogen because it is not combined with other kinds of atoms. Most organisms can use nitrogen only after it has been “fixed”, or combined with other nitrogen-containing compounds.
21 Nitrogen FixationNitrogen fixation is the process of changing free nitrogen into a usable form of nitrogen.It is performed by certain kinds of bacteria that live in bumps called nodules on the roots of legumes (ex: clover, beans, peas, alfalfa, peanuts, and some trees). This is an example of mutualism.Once the nitrogen is fixed, producers can use it to build proteins and other complex compounds. This can happen many times, but eventually the bacteria break down the nitrogen compounds completely and free nitrogen is released back into the air.