Our planet, the earth, is the third planet from the sun in the solar system, and is the only one that has been conclusively demonstrated to be able to support life. Most scientists attribute earth's habitability to the presence of large amounts of water, (nearly 71 percent of the earth's surface is covered by either salt or fresh water) as well as to its perfect proximity to the sun.

All life on earth is collectively termed the "biosphere". Hundreds of millions of species of plants, animals, bacteria, and viruses inhabit every bit of the earth's inhabitable space. Of all of the species in the biosphere, humans create the greatest impact on the earth.

The earth provides natural resources for its over six billion human inhabitants. Some of these resources are essential for our survival, like clean air; others like diamonds and other precious gems are less essential. Humans also rely on the earth to provide many different types of fuel to create warmth and enable transportation. The demands that we place on the earth are great!

The resources that the earth provides are generally divided into two categories: renewable and non-renewable. By definition, renewable resources are able to naturally regenerate themselves. Renewable resources include water, forests (and other plants,) and land for growing crops and raising livestock. Non-renewable resources, once gone, cannot be replaced in a human's lifetime. Fossil fuels such as coal and oil and minerals like gold and iron are examples of non-renewable resources.

Humans and the earth live in a delicate balance. We produce great amounts of waste, tend to overuse land, and sometimes consume too many natural resources, which is harmful to the biosphere. For example, consumption of fossil fuels generates carbon dioxide (CO2), which in turn has been implicated in an increase in global warming and a decline in air quality. Fortunately, humans have the ability to be good stewards of the earth. By using science and technology to create and find alternative means of producing energy, monitoring our energy consumption, and controlling air and water pollution, we will be able to keep our relationship with the earth in steady equilibrium.