ecology and ecosystems—part...

Ecology and Ecosystems—Part One

WE LIVE in a complex world. Many

different species of organisms

have niches in this world and share the

earth’s environment. These niches pro-

vide for the well-being of these living

organisms. Understanding relationships

and systems helps humans relate to

the world in which they live, as well as

care for and improve the environment.

In this E-unit you will learn about ecol-

ogy, ecosystems, natural selection, suc-

cession, homeostasis, and communi-

ties found in nature.

Objectives:

� 1. Define ecology and ecosystems.

2. Explain natural selection and succession.

3. Define homeostasis.

4. Identify communities found in nature.

Key Terms:

�

Meaning of Ecology and Ecosystems

Living things are found in many places on the earth. Important relationships exist between

living organisms and the nonliving features of their environment, such as air, water, and rocks

E-unit: Ecology and Ecosystems—Part One

� AgEdLibrary.com

Copyright © by CAERT, Inc. — Reproduction by subscription only. 020031

biological homeostasis

community

dominant species

ecology

ecosystem

habitat

homeostasis

homeotherm

natural selection

succession

and soil. Humans are better in using and caring for resources on the earth if they understand

some of the relationships that exist.

Ecology is the scientific investigation of the shared life of organisms in their natural envi-

ronment. Living things relate to each other as well as to the physical features in their environ-

ment. Some animals use others

for food. Other animals use plants

for food. All require space and

features within that space that

support their well-being.

An ecosystem is all the liv-

ing things in an area and their

interrelationship with each other

and with their environment.

Many interactions occur, such as

those among the varied species in

the water of a pond—fish, frogs,

turtles, and insects, as well as

plants and microorganisms. These

interactions allow species to exist

in an environment and fill certain

niches. A niche is the unique role

or function of a species within an

ecosystem.

Natural Selection and Succession

Among the important relationships and processes in an ecosystem are those related to natu-

ral selection and succession. The organisms found in an ecosystem are, in one way or another,

products of these two processes.

Natural selection is the process by which those organisms that are best adapted to an

environment survive. Organisms that cannot adapt will not survive and may become extinct—

for example, the dinosaur.

The water in a stream is usually continually flowing. Organisms are moving about. Rocks

and other structures are continually washing and wearing away. Gradual changes may create

conditions in which a species cannot survive. For example, if water in a cool-water trout

stream gradually warms over time, the species of trout must adapt or it will cease to survive.

Other species of fish that are better suited to the new, warmer-water environment will survive.

Areas of land are sometimes changed by fire, farming, residential development, and other

means. The land may no longer be able to support living organisms as it once did. Through

succession, the land area may again support living organisms. The species will vary and change

as the area overcomes destruction.


� AgEdLibrary.com


FIGURE 1. Deer fill a niche in their ecosystem. (Courtesy, Natural Resources

Conservation Service, USDA)

Succession is the natural process of one com-

munity being gradually replaced by another. It is

related to selection or survival of those species that

can adapt. An example is a forest area that has been

burned. No trees will be found the first year.

Soon, small grasses and other plants will begin to

grow. Then, trees will emerge and develop into

mature specimens. As the plants develop, species

of animals will change.

Fortunately, people have learned that they can

promote succession. Trees can be planted, animals

can be released, food can be provided for animals,

and other steps can be taken to speed up the slow

process of natural succession.

Homeostasis

Homeostasis is the tendency of an organism

or other system to maintain relative stability in a

changing environment. It involves self-regulation

to achieve needed conditions. In simple terms,

homeostasis is sometimes compared to a thermostat that regulates the temperature in a house.

The outside temperature may become very cold. The thermostat and heating system keep the

inside of the house at a relatively constant temperature.

Living organisms have biological homeostasis. Biological homeostasis relates to how

living, multicellular organisms must have consistent internal conditions in order to survive.

Water and minerals, nutrients, temperature, waste removal, and other factors may be a part of

biological homeostasis. The requirements vary with the species of organism. We typically asso-

ciate biological homeostasis with animals. Biological homeostasis is also important to plants

and other species.

Osmoregulation is homeostasis as related to water and minerals in an organism. Nearly all

species must have at least some water to carry out life processes. Without water, an organism

will die. Plants take in water through their roots and transport it to stems, leaves, flowers, and

fruit. The water level in a plant is kept at a relatively constant level. Deficiency may result in a

plant wilting. Animals also need a certain level of water, or they become dehydrated. Animals

typically ingest water as they do food.

Excretion is the process of eliminating wastes from the body. A buildup of wastes is harmful

and can lead to disease and death. In some animals, such as mammals, the kidneys and lungs

are responsible for much excretion. Other animals use excretory systems adapted to their

needs. Plants also excrete wastes, such as oxygen and other gases, including water vapor.


� AgEdLibrary.com


FIGURE 2. A wildlife conservationist is checking a bird-

nesting facility near a wetlands area. (Courtesy,

Natural Resources Conservation Service, USDA)

Regulation of body temperature is important in some animals. A homeotherm is an ani-

mal that maintains a constant body temperature without regard to the temperature of the envi-

ronment in which it is living. Energy is required for a homeotherm to maintain its temperature

in cold weather. In warm weather, sweat glands, panting, and other means are used to keep the

body cool. We have often referred to homeotherms as warm-blooded animals. Examples are

mammals and fowl. Fish, amphibians, and reptiles are poikilotherms, meaning that their body

temperature is in relative equilibrium with the environment in which they are living. The

poikilotherms are often referred to as cold-blooded animals.

Communities in Nature

Plants, animals, and other species have a community arrangement. A community is a

group of organisms that live together in relative harmony. The organisms include animals,

plants, fungi, and others. The nonliving features of the environment have a strong influence

on the nature of a community. Climate also influences the nature and kinds of organisms that

live in a community. Organisms in a community often depend on and attract each other.

Some species in a community are dominant. A dominant species is one that is stronger

or larger than the others and uses its strength or size to its advantage. In some cases, the large

number of individuals of a particular species makes that species dominant. This would be true

in a forest that is predominantly oak trees.

Species diversity is important in a community to assure health of the organisms. Some

organisms must rely on others for food, and this creates a certain pressure on the population of

food-source organisms. For example, deer consume browse (twigs and leaves of plants). Their

consumption tends to reduce growth of these plants.

Species will have habitats within a community. A habitat is an area where a species lives in

natural conditions. Habitat requirements vary from one species to another, but all organisms

within a species require a habitat within a certain range of conditions. A habitat must provide

food, shelter, and other needs of a species. If it does not, the species must adapt, or it will cease

to live in the particular location. Habitats are not exclusive. Most have a mix of species, though

certain factors may make a habitat better suited to one species than another.


� AgEdLibrary.com


FURTHER EXPLORATION…ONLINE CONNECTION: Natural Selection

Natural selection is the process by which favorable traits in a species become more pronounced in

succeeding generations. These traits help the species adapt to changes and survive over time. Investigate

more about natural selection at the following Web sites and assess its merits.

http://en.wikipedia.org/wiki/Natural_selection

http://www.wcer.wisc.edu/ncisla/muse/naturalselection/

Communities may be grasslands, pine forests, hardwood forests, wetlands, streams, lakes,

rocky outcrops, and other areas that attract and meet the needs of particular species. Every spe-

cies needs certain habitat features in the community where it lives along with other species.

Summary:

� Important relationships exist between living and nonliving things in the environ-ment. Ecology is the scientific investigation of the shared life of organisms in theirnatural environment. Natural selection occurs in ecosystems by allowing those spe-cies that are strongest and most fit to survive. Damaged areas restore themselvesthrough the process of succession. This allows areas of land to develop through suc-cessive stages of young grasses and small plants with small animals into areas withlarger plants and larger animals. Within an environment, organisms vary in howthey adapt. Some try to maintain a relatively stable condition even though the con-ditions in the environment may change.

Organisms form communities that strive for balance though they never quiteachieve it. Since some species are dominant, lesser species in a habitat are subject topopulation changes.

Checking Your Knowledge:

� 1. What is ecology? What is an ecosystem?

2. How is natural selection important in an environment? What is succession?

3. What is homeostasis?

4. What is a community? What is the role of a dominant species in a community?

Expanding Your Knowledge:

� Use print media and/or the Internet to read and learn more about the meaning andimportance of ecology and ecosystems. Prepare a brief report.

Web Links:

� The Illinois Department of Natural Resources

http://www.dnr.state.il.us/

Ecology.Com

http://www.ecology.com


� AgEdLibrary.com


ecology and ecosystems—part...

Documents