Key Points
Key Points will give you the main information you should know to teach the activity.

• Water is necessary for life. Living things depend on water to help digest and break down food, to keep the body at a constant healthy temperature, to transport nutrients, to carry out wastes and as an ingredient in chemical reactions. Without water, an organism would soon die.

• Because organisms need water to survive, all habitats must contain some amount of water for organisms to live there.

• South Carolina is a state that receives a high amount of rainfall, and thus has abundant water in most parts of the state. The availability of water leads to a great diversity of habitats and organisms in the state.

• All the water in South Carolina flows across the state from the mountains to the sea to eventually join into the ocean.

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Detailed Information
Detailed Information gives more in-depth background to increase your own knowledge, in case you want to expand upon the activity or you are asked detailed questions.

Without water, there would be no life on earth. Single cell organisms and most of the cells in multicellular organisms need to be submerged in water to survive. The cells themselves are comprised of approximately 70 to 90 percent water. Water, in liquid form, covers 75% of the Earth’s surface as oceans, rivers, streams, lakes, creeks and ponds. Water appears on our planet in solid form as ice sheets, icebergs, sleet, snow, and hail and in its gaseous form as water vapor, visible to us as steam. Water, in its liquid form, is suspended in gas in the form of mist and fog and, in both solid and liquid forms, is suspended in gas in the clouds. Water is the only common substance to exist in the natural environment in all three physical states of matter: liquid, solid and gas. Water is truly an amazing substance with extraordinary properties.

A water molecule, at first glance, is quite simple. It is comprised of one atom of oxygen and two atoms of hydrogen.

What makes water special is that one side of the molecule carries a positive charge (the side where the hydrogen atoms are located) and one side carries a negative charge (the side where the oxygen atom is located). A molecule that contains opposite charges on opposite sides of itself is called a polar molecule. The polarity of water gives water its unusual properties. The positively charged hydrogen atoms of one molecule of water are attracted to the negatively charged oxygen atom of a neighboring molecule. The oxygen and hydrogen atoms bond with one another and these bonds are called hydrogen bonds. As a result of hydrogen bonding, water molecules stick together cohesively.

The cohesion (sticking together) of water molecules is one of the properties that makes water so interesting. Cohesion of water molecules at the top of a body of water results in surface tension. Surface tension is the resistance the top of a body of water has to breaking apart and can sometimes give water the properties of a solid. Surface tension can be seen when insects such as water striders walk across the surface of water or when you jump into a pool flat on your stomach and it initially feels like you landed on the ground before you sink in. That pain you feel is caused by surface tension.

Cohesion also enables water in plants to travel from the roots to the leaves. Water enters a plant through its roots and then it is carried up tiny tubes, called the xylem, through the stem to the leaves. In some plants, such as redwood trees, this can be a trip of hundreds of feet. When the leaves open their stomata (the holes in the leaves) for respiration, some of the water molecules in the xylem are lost from the plant to evaporation. The water molecules that evaporate are still attached to the rest of the water molecules in the xylem by cohesion. The evaporating water pulls the water molecules behind it, like a locomotive pulling boxcars. The water molecules at the bottom of the xylem in the roots will pull new water molecules in the roots from the soil. This way, water is continuously moving through the plant by cohesion.

Water is important to living things because of its properties as a solvent and a temperature moderator. Many substances dissolve in water. Because some substances have electrical charges that are attracted to the electrical charges of water molecules, the molecules of these substances will bond with the molecules of the water. This is what happens when salt or sugar is poured into a glass of water. The salt or sugar molecules will bond with the water molecules and, to the eye, seem to disappear. Because of this solvent property, water is necessary for digestion and for transporting substances around an organism’s body. In animals, water helps to break down food into its usable nutrients, and then the water in the blood helps to carry the nutrients to the various cells of the body as well as to carry the wastes out of the body.

The ability of water to maintain a constant temperature is also necessary for keeping living things at a constant temperature. Extreme temperature changes can be fatal to most living things. It takes a lot of energy to raise water even a degree in temperature. Because of this property, high proportions of water in living things help to keep the organism’s body temperature in a limited range conducive for the survival of the organism. The water in the body retains heat when it is cold outside and resists heating when it is hot outside. If it is too hot, water can be released outside of the body in the form of sweat for increased cooling. It takes a great deal of heat to turn liquid water into water vapor (539 calories per gram of water). This heat to evaporate the sweat is taken from the body and the loss of body heat lowers the body temperature.

Water is also very important as an ingredient in chemical reactions. For example, plants produce food in photosynthesis by combining molecules of water with molecules of carbon dioxide. Without the food energy produced during photosynthesis, most living things could not survive.

Because water is being used in so many different ways by living things, it constantly needs to be replenished. The living thing has to regularly intake water to replace water lost during its regular life processes. For this reason, living things can only be found in habitats that contain water.

Luckily, water can be found all across the earth. 75% of the Earth’s surface is covered with water with 70% of the surface covered by the oceans. Water is abundant to living things that can live in saltwater. 97% of water on earth is saltwater in the oceans. Of the remaining 3% that is freshwater, 2% is found as ice in glaciers and polar caps, more than 0.5% is in the ground as groundwater, so less than 0.5% of water on earth is freshwater in rivers, streams and lakes. This freshwater can be found in most land habitats on earth in greatly varying degrees of abundance.

The abundance of water in the habitat will often determine the biodiversity, amount and variety, of life found in the habitat. For example, the tropical rainforests of the Amazon Basin have much higher biodiversity than the Saharan Desert. By the same token, the well-watered habitats of South Carolina have much higher biodiversity than the arid habitats of Nebraska. The presence of large amounts of water allows a larger variety of living things to flourish.

All of South Carolina receives a high amount of annual average rainfall ranging from 45 inches a year in the Sandhills to 80 inches a year in some parts of the Mountains. Look on a map of South Carolina and you will see that each region of the state contains many large bodies of water ranging from mountain streams to rivers to blackwater swamps to salt marshes. The high amount of rainfall helps sustain a high biodiversity in our small state.

Rainfall is just one part of the water cycle, the cycle by which water circulates endlessly from the ocean, the land and the atmosphere. The two primary factors driving the water cycle are evaporation (the change from liquid to gas, such as water vapor) and precipitation (rain, sleet, hail and snow). The heat from the sun causes water on earth to warm and to evaporate. As it rises, the water vapor cools and forms clouds. Precipitation in the form of rain occurs when water cools and condenses (the transition from water vapor to liquid) around small particles and the water falls to the ground. Precipitation in the form of sleet and snow occurs when water freezes around small particles and the water falls to the ground.

Because the ocean covers 75% of the Earth’s surface, most precipitation falls into the oceans, where it stays until it eventually evaporates again into the atmosphere. The water in precipitation that falls on land can do one of several things. Most of the water that falls on the ground will end up seeping into the soil where it will either be collected by plant roots and brought into a plant or will become part of the groundwater. Groundwater is all of the water that collects in the spaces between rocks underneath the surface. The groundwater will flow slowly towards the ocean and eventually may resurface to feed a stream, swamp or other body of water. Some of the water that falls on land as rain will travel downhill across the land as runoff to join larger bodies of water, such as lakes, streams and ponds.

All of the water on land is part of a watershed. Watersheds are areas of land where all of the rainwater that falls in that area eventually drains into a particular body of water. South Carolina has four major watershed areas: one that drains into the Savannah River, one that drains into the Santee River, one that drains into the PeeDee River and a collection of smaller watersheds all contained within the Coastal Plain, which drain into such rivers as the Edisto and the Ashley. All of the watersheds in South Carolina eventually flow into the ocean, because elevation drops as you travel from the mountains to the sea across South Carolina. Some of the water in these watersheds may evaporate before it reaches the ocean, and become part of the atmospheric water and then continue the cycle again.

Water in watersheds flows through many habitats and all of the organisms that live in the habitat depend on it for survival. Our planet is unique among the ones we know because of its abundance of liquid water and its abundance of life. It is the presence of liquid water with all of its amazing properties that have allowed life to flourish on Earth.