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Ecology and Ecosystems—Part One
W
E LIVE in a complex world. Many
different species of organisms
have niches in this world and share the
earth’s environment. These niches provide 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 ecology, ecosystems, natural selection, succession, homeostasis, and communities found in nature.
Objectives:
þ
1.
2.
3.
4.
Define ecology and ecosystems.
Explain natural selection and succession.
Define homeostasis.
Identify communities found in nature.
Key Terms:
Ñ
biological homeostasis
community
dominant species
ecology
ecosystem
habitat
homeostasis
homeotherm
natural selection
succession
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
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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 environment. Living things relate to each other as well as to the physical features in their environment. 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 living 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 FIGURE 1. Deer fill a niche in their ecosystem. (Courtesy, Natural Resources
niches. A niche is the unique role Conservation Service, USDA)
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 natural 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.
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Succession is the natural process of one community 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 FIGURE 2. A wildlife conservationist is checking a birdnesting facility near a wetlands area. (Courtesy,
or other system to maintain relative stability in a
Natural Resources Conservation Service, USDA)
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 associate 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.
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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/
Regulation of body temperature is important in some animals. A homeotherm is an animal that maintains a constant body temperature without regard to the temperature of the environment 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.
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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 species needs certain habitat features in the community where it lives along with other species.
Summary:
2
Important relationships exist between living and nonliving things in the environment. Ecology is the scientific investigation of the shared life of organisms in their
natural environment. Natural selection occurs in ecosystems by allowing those species that are strongest and most fit to survive. Damaged areas restore themselves
through the process of succession. This allows areas of land to develop through successive stages of young grasses and small plants with small animals into areas with
larger plants and larger animals. Within an environment, organisms vary in how
they adapt. Some try to maintain a relatively stable condition even though the conditions in the environment may change.
Organisms form communities that strive for balance though they never quite
achieve it. Since some species are dominant, lesser species in a habitat are subject to
population 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:
L
Use print media and/or the Internet to read and learn more about the meaning and
importance 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
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