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HO CHI MINH UNIVERSITY OF INDUSTRYINSTITUTE FOR ENVIRONMENTAL ENGINEERING & MANAGEMENTCompiled by VO DINH LONGENVIRONMENTAL SCIENCES(Specialized English course for Environmental Students)HO CHI MINH CITY - 2006 CONTENTS2 CHAPTER 1: BASIC UNITS OF ECOLOGYAfter studying this chapter, you should be able to: 1. Define environment.2. Define an ecosystem.3. Identify the components of the biosphere.4. Describe the living and nonliving components of the environment.5. Explain that bacteria and fungi are agents of decay.6. Discuss the process of photosynthesis.7. Enumerate the important factors that affect the growth of plants and the survival of animals.1.1. THE ECOSYSTEMWhen God created the world, He said, “Let the earth produces all kinds of plants, those that bear grain and those that bear fruit”, and it was done. Then He also created animals, including human beings and provided light. God, therefore, saw to it that everything needed for them to live is found in the world which He created. He provided space, ways and means by with different organisms can interact with one another and with their environment. Part of the world where life operates is known as the biosphere.The biosphere consists of the air (atmosphere), water (hydrosphere), and earth (lithosphere) where living things interact with their environment.Figure 1.1: The biosphereWhen you study the interaction or relationship between organisms and their environment, you are studying an ecosystem. The term ecosystem refers to all the living things and the nonliving things in a given area. It includes all the plants and animals together with their surroundings. The ecosystem of an aquarium, for example, consists of the hydrilla and others plants, fish, snails, and other aquatic animals, 3 some of which can only be seen under a microscope. It also includes sand and pebbles at the bottom. We can also include the owner who takes care of the aquarium.A grassland, too, is an ecosystem. This ecosystem consists of the grass, earthworms, insects, bacteria, soil, water, sunlight, and other plants and animals that live on it. The pond is another example of an ecosystem. The forest is a more complex ecosystem. Can you identify some of the components of this ecosystem?The entire earth can be thought of as an ecosystem. It has an abundance of different kinds of species of living things which, although separate by great distances, still react with one another and with the nonliving world. In a forest ecosystem, interrelationships among its living and nonliving components occur. The branches and leaves of trees help break the force of the rain. Layers of dead leaves and twins and branches on the forest floor soak up water and prevent rain from washing soil away. Little water runs off the land. The roots of trees hold the soil and water on which they depend. Moreover, when the leaves and branches decay, they become part of the rich topsoil. The soil is made up of minerals like silica and clay. They come from the breakdown of rocks. There are spaces between the mineral particles which are filled with air and water. Roots of plants penetrate deeper into the soil causing physical change. They loosen the tightly packed particle. Chemical change also occurs. The roots absorb the minerals present. Figure 1.2: Plant-soil relationshipThere are thousands of organisms that live in the soil, like earthworms, that decompose the dead plants and animals. Some are too small to be seen, but they all help maintain the ecological balance in the soil.4 Figure 1.3: Organisms in the soilGuide questions1. What is an ecosystem?2. How do the living components of an ecosystem affect the nonliving components? Give example. 3. Can a fallen log be considered as an ecosystem? Explain your answer.1.2. COMPONENTS OF AN ECOSYSTEMIn the preceding section you learned what an ecosystem is. The living component is known as the biotic and the nonliving component is known as abiotic. The biotic component consists of plants, animals, and bacteria. The abiotic component includes all the factors of the nonliving environment such as the substratum, light, rainfall, nutrients, soil, and others. Both the biotic and abiotic components are equally important in the ecosystem because without one of them the ecosystem would not function. InsightfulnessThe ecosystem consists of the biotic and abiotic components. The biotic components are the plants, animals, and decomposers. The abiotic components are the non living factors, such as temperature, water, and others. The abiotic affect the biotic components and vice versa. 1.2.1. Green plants Green plants are known as the producers. They capture the energy from the sun and together with carbon dioxide (CO2) in the air and water (H2O) convert together those into food energy. Since plants are able to manufacture their own food, they are also known as autotrophs (or self-nourishing). These plants are able to manufacture food though the process of photosynthesis, which will be explained in the next section. Green plants also take substances, such as nitrogen and sulfur from the environment and convert those into plant materials that can be used by other organisms as food. These green plants further provide oxygen which is taken in by humans and animals in the process of respiration. For these reasons, all life, whether in the pond, forest, or grassland, depend on green plants.5 You might think that green plants consist only of the trees or big plants that you see around. The other producers are invisible to your eyes. These are the microscopic drifting plants which are greater sources of food than the big plants that you can see. We call these microscopic plants phytoplankton. When they become too abundant, they can give a pond or a body of water a green color. Have you ever seen a pond or a lake with green surface?Guide questions 1. What are producers?2. What do producers perform in an ecosystem?3. What are phytoplanktons?1.2.2. AnimalsAnimals, or the consumers, obtain their food from plants or other animals. Because of this, they are also known as heterotrophs, which means that they feed on others and cannot manufacture their own food, unlike the green plants. There are three different types of consumers, namely, the herbivores, the carnivores, and the omnivores.Figure 1.4: There are three different types of consumersThe herbivores are those that eat plants only. For example, the caterpillar that feeds on leaves is an herbivore while the snake that eats the caterpillar is a carnivore. Omnivores eat both plants and animals. A human being is a good example of an omnivore. Through the process of respiration, animals combine the food they eat with oxygen to produce CO2 and H2O which are used by plants in the photosynthesis process. Animals also convert the materials of the plant bodies into the materials that make-up their own bodies. All the energy produced and used by animals comes from the plants. Guide questions 1. What are consumers?6 2. What are the three types of consumers? and give one example for each type. 1.2.3. Bacteria and fungi as agents of decayHave you ever observed what happen to leaves that fall on the ground? After some time, the leaves wither, break down into smaller pieces, decay, and finally become part of the soil. What do you think is responsible for this change?Have you heard of the word decomposer? What do you think does a decomposer do?Decomposers make-up the third biotic component of the ecosystem. They use the bodies of dead animals and plants for their food. The materials contained in these dead bodies are broken down by the decomposers, thus they get the energy they need and release the minerals and other nutrients back into the environment for use again by other organisms. Bacteria are among the most abundant decomposers while fungi are known to be the fast-acting decomposers. Decomposers are found everywhere. In the pond, they are abundant at the bottom where the remains of the dead organisms (plants and animals) settle. On land, they abound on the surface of the soil where the dead bodies of plants and animals are found. Each of the three groups of the biotic component of the ecosystem - producers (plants), consumers (animals), and decomposers (bacteria and fungi) - has its own specific function or task to perform.Figure 1.5: Relationship among biotic component of the ecosystem7 The work performed by an organism is known as its ecological niche, while the place where the organism lives in the ecosystem is known as its ecological habitat.Guide questions1. What are producers?2. Give examples of producers?3. What do decomposers perform in the ecosystem?1.2.4. Nonliving factorsThe nonliving factors of the environment make-up abiotic component of the ecosystem. These include the chemical and physical factors in the environment, such as light, temperature, water, pH (acidity), wind, chemical nutrients, salinity (saltiness), soil, and others. Organisms are affected by the biotic factors simultaneously but, of course, different species of organisms are affected differently. For example, lichens may not survive when temperature gets very high but cactus may. Different organisms thrive in different conditions. There are animals, like the earthworms, which favor wet condition, while others, like ants, prefer drier conditions. Some plants, such as cactus, grow best in sandy soil while tomatoes grow best in loamy soil. As a whole, these environmental factors not only provide essential energy and materials but also determine the kind of organisms that will inhabit the area. Hence, they provide the conditions necessary for the survival of the organisms. Guide questions1. What are the components of an ecosystem?2. Give examples for each component of the ecosystem.3. In general, what are the functions of these components?4. Can an ecosystem exists without one of its components? Justify your answer. VocabularyAutotroph: Organism that is self-nourishing; one that can produce its own food. 8 Hetertrop: Organisms that feeds on others and cannot manufacture its own food. Biological magnification: Accumulation or increase of chemical substances on organisms in succeeding higher trophic levels.Biomass: Amount of organic materials in plants or animals from which energy can be derived. Energy: Capacity to do workEnergy content: The amount of energy available for doing work. For example, the amount of energy in fuel available for powering a motor vehicle.Food chain: Energy pathway which proceeds from the producers to the consumers. Food web: Series of interrelated food chains in an ecosystem. Pyramid of energy: Representation of the organic content in each trophic level.Biosphere: Portion of the earth and its environment within which life in any of its form is manifested. Photosynthesis: Process of manufacturing food by green plants in the presence of sunlight.Atmosphere: Layer of air surrounding the earth. Hydrosphere: The part of the Earth composed of water including clouds, oceans, seas, ice caps, glaciers, lakes, rivers, underground water supplies, and atmospheric water vapor.Lithosphere: The outer, rigid shell of the Earth, situated above the atmosphere and containing the crust, continents and plates or the solid part of the earth’s surfaceGrassland biome: Community where grass is abundant while trees are scarce and where mostly herbivores and rodents dwell.Carnivore: Animals that get food from killing and eating other animals.Herbivore: Organisms that eat plants only. Omnivore: Organisms that consume both plants and animalsBiotic factor: Living component of the ecosystem which includes plants, animals, and bacteria. Biotic potential: Reproductive capacity of the living components of the ecosystem.Producer (autotroph): Green plant or organism that, performs photosynthesis. Consumer: Organism that feeds on other organisms. 9 Decomposer (also known as microconsumer): Organism which breaks down nonliving organic material; example are bacteria and fungi.Environment: Sum of all external forces and conditions acting on an organism or a community of organisms.10 123doc.vn
