Ecosystems and Changes: Investigation 3

Adaptations

In Investigations One and Two, students investigated food chains and food webs. In this Investigation, students will learn how populations of organisms develop structures that allow them to survive in a particular ecosystem. Students will perform experiments that model the survival of two different kinds of plants in two separate ecosystems– wetlands and forests.

Wetlands

Wetlands may be defined as an area of land that is periodically covered by water and contains soil with a great deal of moisture. They are typically located between land and bodies of water. Wetlands serve as an important buffering system. They can hold water in times of flooding and release water in times of drought. Plants that live in wetlands are termed hydrophytes (water-loving plants). A typical coastal wetland is pictured below.

Typically, there is very little oxygen in wetland soil because it is usually covered with water. In order to survive, the hydrophytes have adapted to live in soil that lacks large amounts of oxygen. Thus, hydrophytes often have sturdy hollow tubes in their leaves to transport water and oxygen.

Forests

The forest is another important ecosystem that typically covers a large area of land. Forests are one of the ecosystems most endangered by man, as millions of acres of forest are depleted annually by lumbering operations and development. Forests are characterized by a dense growth of trees, plants, and underbrush or shrubs. Alpine forests, like the one in Switzerland pictured below, typically have predominately evergreen trees such as cedars, firs, and pines. While evergreens lose their needles, they do not lose them all at one time, so the forest remains green throughout the year.

Forest rainfall varies according to its geographical location on Earth. Precipitation usually occurs all year long in one form or another, and forest soil is not dry or marshy wet. Forest plants can therefore take secure hold of the soil and develop into very large trees with intricate and wide-spanning root systems. Below is a photograph of a temperate forest in the autumn. A combination of rain and length of day and perhaps other factors all combine to make autumn in temperate zones some of the most breathtaking colors anywhere on Earth.

Forest trees are among the largest living organisms on Earth and require an enormous amount of water and CO₂ to survive. On the other hand, as producers, they can generate tremendous amounts of oxygen and plant biomass for other organisms in the ecosystem.

Adaptation

In this Investigation, students will perform experiments that model how different root systems provide plants with the ability to survive in different soil water concentrations. These experiments and discussions will strengthen the students’ understanding of the concept of adaptation.