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 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: 1. Define ecology and ecosystems. 2. Explain natural selection and succession. 3. Define homeostasis. 4. Identify communities found in nature. Key Terms: 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 Page 1 AgEdLibrary.com
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 niches. A niche is the unique role or function of a species within an ecosystem. FIGURE 1. Deer fill a niche in their ecosystem. (Courtesy, Natural Resources Conservation Service, USDA) 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. Page 2 AgEdLibrary.com
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 or other system to maintain relative stability in a changing environment. It involves self-regulation to achieve needed conditions. In simple terms, FIGURE 2. A wildlife conservationist is checking a birdnesting facility near a wetlands area. (Courtesy, Natural Resources Conservation Service, USDA) 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. Page 3 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/ 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. Page 4 AgEdLibrary.com
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: 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: 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 Page 5 AgEdLibrary.com