23.4 Lesson 23.4:: Ecosystems
Lesson Objectives
- Explain what an ecosystem is.
- Discuss how biotic and abiotic factors play a role in the ecosystem.
- Explain what a niche is and its importance in an ecosystem.
- Describe what a habitat is and how an organism is adapted to live in the habitat.
Check Your Understanding
- What is a community?
- What are the different types of community interactions?
Introduction
Now that you have studied what a community is, you have seen some of the interactions
that occur between species. The next level, the ecosystem, includes not only the biological
components, but also the abiotic components, all functioning together. You will examine in
more depth biotic and abiotic factors, and how the concepts of the niche and habitat play
important roles in the ecosystem.
What is an Ecosystem?
An ecosystemis a natural unit consisting of all the biotic factors (plants, animals and
micro-organisms) functioning together in an area along with all of the abiotic factors (the
non-living physical factors of the environment). The concept of an ecosystem can apply to a
large body of freshwater, for example, as well as a small piece of dead wood. Other examples
of ecosystems include the coral reef, the Greater Yellowstone ecosystem, the rainforest, the
savanna, the tundra, the desert and the urban ecosystem (Figure23.16).
Ecosystems, like most natural systems, depend on continuous inputs of energy from outside
the system, most in the form of sunlight. In addition to energy being transferred within the
ecosystem, matter is recycled in ecosystems. Thus, elements such as carbon and nitrogen,
and water, all needed by living organisms, are used over and over again. These topics will
be discussed in more detail in theEcosystem Dynamicschapter.
Ecosystems can be discussed with respect to humans as well. A system as small as a house-
hold, neighborhood, or college, or as large as a nation, may then be suitably discussed as a
human ecosystem. While they may be bounded and individually discussed, human ecosys-
tems do not exist independently, but interact in a web of complex human and ecological