Environment

When we speak of environment, we are referring to more than just location. Environment also includes factors such as light, temperature, minerals, pH, and for land plants, the availability of water. For instance, lichens can grow in a great many places: on bare rock; in the arctic tundra at high altitudes and high latitudes (where nearly 500 species are found); in bogs and forests; on rotting logs; and in rural areas on the trunks of trees. Yet they seem not to grow on the trunks of trees in the city, suggesting an aversion to the pollution often found in cities.

Certain species of blue-green algae thrive in hot springs, where the temperature may reach 85°C. Algae live in deep water where no other plants grow. They thrive where only short-wavelength, blue light can reach and out of the reach of longer wavelengths of light. Their capacity to grow in such an environment may relate to their phycocyanin pigment. Some species of algae grow in shade, some in open sun. Many species of algae are so cosmopolitan, they seem to know no boundaries.