The Science of the Environment

Ecology Is the study of the relationships of living things to their surroundings and to one another. The word ecology means the study. Physical factors, or abiotic factors, such as temperature, weather conditions, altitude, water, and light, affect living things. Living things also affect one another. The ways in which organisms affect one another are the biotic factors. For example, many kinds of plants live in a tropical forest. The moist air and warm sunshine provide ideal growing conditions. The trees grow tall and form a canopy over the land. Their spreading branches expose the leaves to the light energy from the sun. However, the dense canopy allows very little light to reach the ground. In this way, the trees affect the environment of other plants below. Plants living on the tropical forest floor have large leaves. This adaptation allows them to trap the small amounts of sunlight that filters through the canopy.

Plants living in an area not only affect one another. The environment they create also affects the animals living there. The green color of many snakes and lizards hides them from enemies as well as from their prey. Many trop­ical forest animals are adapted to climb trees to catch food. Many spend their entire lives crawling among the tree branches.

Adaptations allow organisms to live in specific environ­ments. Differences in the structure of an organism are adaptative if they help the organism survive. For example, if you transplanted a large-leaved tropical forest plant to the desert, it would wilt and die. Also, if you were to trans­plant a cactus to the tropical forest floor, it would not receive enough energy to support life. It also would die. All organisms depend on their surroundings for the activities of life.

Patterns

The many different kinds of plants and animals are grouped according to common characteristics. These char­acteristics are the patterns that are identified by observa­tion. A biologist then forms hypotheses to reason how these patterns could have developed. As you read in Chapter 13, Charles Darwin proposed his theory of evolution to explain the basis for patterns in living things.

Ecologists work everywhere in the world. They look closely at the homes of all forms of life. Any forest, field, pond, lake, or ocean where life exists can be a laboratory to an ecologist. Ecologists also look for patterns. Then they seek explanations to show how the patterns develop.

The Biosphere

The biosphere is the thin layer where life exists on earth. In the biosphere, an individual organism is a fundamental unit of ecology. How does an individual fit into a larger pattern? How do we look at the entire biosphere and find a pattern? Let's begin by looking at some factors common to all life on the earth. Consider the earth as one gigantic sys­tem of interacting factors.

Three kinds of relationships occur in the biosphere: 1) Interactions take place among the biotic factors: 2) Inter­actions take place among the physical factors: and 3) Inter­actions take place between the biotic factors and the physical factors. These are patterns that can be observed and studied.

Interactions Among Biotic Factors

Animals that depend on plants for food are naturally found where the plants are living. Animals that eat plant-eating

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