Watch a video clip and do the exercises.
n. [C, U] the natural home or environment of an animal, plant, or other organism
n.[C] a very tall North American tree that can live a very long time
The diversity of life on earth isastounding. Organisms both large and small have adapted to the many different habitats onthe planet. And along the way, they have developed unique traits and methods ofsurvival. But at a microscopic level, all living organisms are very similar. They are all made of cells. A single cell contains the information that determines all the organisms' characteristics. A giant sequoia in California begins as a single cell andeventually grows to be one of the largest trees in the world. As the fundamental unit of life,the structure and function of cells dictate many of the basic behaviors of livingorganisms. Animals eat, because their cells need energy, and they breathe, because theircells need oxygen. Cells are able to function and thrive on their own. Unicellular organisms are so successful that they can be found in every habitat on earth, no matter how extreme. Withoutcells, life, as we know it, would not exist. Life on earth is diverse, but it all can be traced to a single building block—the cell.
