Components of Ecosystem PDF

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Ecosystem Introduction: Environment is a life supporting system. Environment involves both living organisms and the non-living physical conditions. These two are inseparable but inter-related. For food, shelter, growth and development, all life systems interact with the environment. In the subject of ecology, the term ecosystem refers to the environment of life. It is a selfsustaining, structural and functional unit of biosphere. An ecosystem may be natural or artificial, land- based or water-based. Artificial systems may include a cropland, a garden, a park or an aquarium.

In this leacture, we are going to learn the following modules: 1. Definition of an Ecosystem 2. Biotic Components 3. Abiotic Components 4. Functions of an ecosystem 5. Processes of ecosystems 1. DEFINITION OF AN ECOSYSTEM The living community of plants and animals in any area together with the non-living components of the environment such as soil, air and water, constitute the ecosystem. The living organisms of a habitat and their surrounding environment function together as a single unit. This ecological unit is called as an `ecosystem'. An ‘Ecosystem’ is a region with a specific and recognizable landscape form such as forest, grassland, desert, wetland or coastal area. The nature of the ecosystem is based on its geographical features such as hills, mountains, plains, rivers, lakes, coastal areas or islands. It is also controlled by climatic conditions such as the amount of sunlight, the temperature and the rainfall in the region. The geographical, climatic and soil characteristics form its non-living (abiotic) component. These features create conditions that support a community of plants and animals that evolution has produced to live in these specific conditions. The term ecosystem first appeared in a publication by the British ecologist Arthur Tansley, during 1935. An ecosystem may be of very different size. It may be a whole forest, as well as a small pond. Different ecosystems are often separated by geographical barriers, like deserts, mountains or oceans, or are isolated otherwise, like lakes or rivers. As these borders are never

rigid, ecosystems tend to blend into each other. As a result, the whole earth can be seen as a single ecosystem, or a lake can be divided into several ecosystems, depending on the used scale. The ecosystem is an open system. It receives energy from an outside source (the sun), as input, fixes and utilities the energy and ultimately dissipates the heat into space as output. An ecosystem has a physical environment, or factors, biological components and interactions between them. Any ecosystem is characterized by a set of abiotic and biotic factors, and functions. The organisms in an ecosystem are usually well balanced with each other and with their environment. Introduction of new environmental factors or new species can have disastrous results, eventually leading to the collapse of an ecosystem and the death of many of its native species. The abstract notion of ecological health attempts to measure the robustness and capacity for recovery of a natural ecosystem. Within an ecosystem, all living things have a habitat or the physical area in which they live. The habitat of an organism may include many different areas. For Example, a mouse can be seen in a field, garden or even in a house. Animals that migrate will have different habitats during different seasons. Some birds that live in a place during summer spend the winter in some other place. Macro and Microecosystems: The dimension and spread of an ecosystem may vary. Depending upon their existance and dimension, ecosystems are classified as Macroecosystems and Microecosystems. Dimensionally larger systems such as a forest or a lake are called as macroecosystems. Life scientists and environmental biologists who are interested to evaluate the functional mechanisms of an ecosystem, may create an experimental setup in the field or in the laboratory. Such setup are considered to be microecosystems. Depending upon their matrix of research, it may be a terrestrial microecosystem, or an aquatic microecosystem. 2. BIOTIC COMPONENTS Biotic components - include all living organisms and their products. This group includes all animals, plants, bacteria, fungi and their waste products like fallen leaves or branches or excreta. Based on their activity, biotic components are classified into four categories as a) producers b) consumers c) transformers and

d) decomposers. Let us discuss these categories: PRODUCERS: Producers are called energy transducers. They convert solar energy into chemical energy, with the help of organic and inorganic substances. The producers are called as autotrophic ( auto = self; troph = nourishing) organisms. They are capable of synthesizing food from non-living inorganic compounds. They are largely represented by green plants on land (trees, grasses, crops) and phytoplanktons on water. CONSUMERS : Consumers are the organisms, whose food requirement are met by feeding on other organisms. They consume the food materials prepared by the producers (autotrophs). Hence, consumers are called as heterotrophic organisms. Animals belong to this category. Depending upon their food habits, consumers are classified into primary, secondary and tertiary consumers. The PRIMARY CONSUMERS are solely feed on plants. Herbivores are plant eaters - grasshopper, rabit, goat, sheep are primary consumers. The SECONDARY CONSUMERS feed on some primary consumers. Carnivores-are flesh eaters. Eg. - Hawks ,Tiger and Lion. Omnivores (Biophages ) - eat both vegetables and flesh( cockroaches, fox, humans). Secondary consumers are those which predate on primary consumers. Eg. several species of insects and fishes. TERTIARY CONSUMERS are the predators of predators. They are mostly larger animals. TRANSFORMERS : Transformers are certain types of bacteria . They attack on materials excreted by other living organisms (even dead plants and animals ). They transform the above into either organic or inorganic substances. These substances are suitable for the nutrition of green plants. Transformers help in recycling the nutrients which came as waste already. DECOMPOSERS : They are also called as microconsumers. They depend on dead organic matter for their food . They are chiefly micro organisms like bacteria and fungi. They break the complex organic matter found in plant and animal bodies, and release simple substances . These substances will be used

by autotrophs once again. Some invertebrate animals like protozoa and earthworms use these dead organic matter for their food. They are called as secondary decomposers.

3. ABIOTIC COMPONENTS The abiotic components are the non-living components of the ecosystem. They are of three categories 1. Climatic and physical factors -air, water, soil and sunlight; rainfall, temperature, humidity, soil texture and geomorphic conditions. 2. Inorganic substances- There are various nutrient elements and compounds, such as carbon, nitrogen, sulfur, phosphorous, carbon-di-oxide, water, etc. 3. Organic compounds- These are proteins, carbohydrates, lipids, humic substances, etc. They largely form the living body and link the abiotic compounds with the biotic factors. The abiotic factors determine the type of organisms that can successfully live in a particular area. Some of the major non-living factors of an ecosystem are: Sunlight Water Temperature Oxygen Soil Air * Sunlight is necessary for photosynthesis; it influences organisms and their environment; it has a profound effect on the growth and development of life. * Water is the elixir of life; all living things require water for their survival, but some can live with lesser amounts * Temperature -- all living things have a range of temperatures in which they can survive; beyond those limits it will be difficult for them to live. * Oxygen -- many living things require oxygen; it is necessary for cellular respiration, a process used to obtain energy from food; others are actually killed by the presence of oxygen (certain bacteria) * Soil -- the type of soil, pH, amount of water it holds, available nutrients, etc determine what type of organism can successfully live in or on the soil; for example, cacti live in sand, cattails in soil saturated with water. The inorganic substances like nitrates, carbonates and phosphates occur either freely or in the form of compounds dissolved in water and soil. Some of them are recycled by micro-organisms on the dead bodies of plants and animals. 4. FUNCTIONS OF AN ECOSYSTEM: A system is an organization that functions in a particular method. The functions of an ecosystem include

1) Flow of energy through the medium of living organisms and their activities 2) Food chains 3) Biodiversity and biomass 4) Circulation and transformation of elements and nutrients 5) Development and evolution and 6) Control. Energy is also consumed by the autotrophs at cellular level for the reactions related to 1. growth 2. development 3. maintenance and 4. reproduction. The specific functional processes of an ecosystem include a) photosynthesis, b) decomposition, c) predator - prey relations (herbivory, carnivory, parasitism and d) symbiois. Directly or indirectly the ecosystem's functional concept is useful in the management of renewable resources such as forests, watersheds, fisheries, wildlife and agricultural crops and stock. 5. THE INTERNAL PROCESS Photosynthesis (Ps) and respiration (Rp) are the two major processes involved in the production and transformation af energy. The rate of photosynthesis increases by an increase of temperature. Many other factors influence the process of photosynthesis. However, it is involved 1) in the intake of radiant energy and CO2 and 2) release of oxygen. Respiration is involved in the uptake of oxygen and release of CO2 and energy. The total synthesis of organic matter resulting from the exposure of light can give the Gross Primary Production. The amount of organic matter stored after expenditure (in terms of respiration) is called as the Net Primary Production. Hence, Primary Production is the amount of organic carbon and Primary Productivity is the rate of production. The net primary productivity is also called as apparent photosynthesis or net assimilation. The grain, straw, stalks, roots, etc harvested from a paddy field ( after a growing. season) comprise the net primary production.

Net Primary productivity = Gross Primary productivity - Respiration

It is well known that animals are not capable of synthesizing their food. So, they have to rely upon other plants and animals for their food. There are two biological processes involved in animal life. They are 1. Metabolism and 2. Growth. They require energy which is obtained from the ingestion of food. The food, which is in excess of the metabolic needs, is used to produce animal tissue. This process is known as secondary production. It is estimated by measuring the increase in weight or size of the animals over a period of time. So, secondary productivity is the amount of new organic matter stored by the consumers or the heterotrophs. It is a function of the amount of primary production in an ecosystem. The total quantity of organic matter present at any given time in an ecosystem, is called as the biomass. Life in Ecosystems need a continuous supply of energy for survival. Almost all the energy available to us on earth comes from the sun. The radiation gives heat and light. The uneven heat develops the wind to blow. The radiation evaporates water into the air and the evaporated molecules arc returned back as rain. Plants are fundamental to all life on earth. Because, plants have the ability to trap solar energy falling over them and use this energy to build living tissues. This process is called photosynthesis. During this process, the inorganic energy - poor molecules (CO2 and water) are converted into organic -rich food molecules (sugars). In this way, plants do not need to depend on other organisms. Hence, they are treated as self nourishers or autotrophs. Animals can not use the sun in this way. So, they are dependent, directly (or) indirectly, on plants for food. Hence, animals are treated as other nourishers or heterotrophs. The energy used during photosynthesis by plants is not lost. Sugar is a product of photosynthesis. This sugar contains stored chemical energy and can be burnt to produce heat. Now, in this process, CO2 and water are released as by-pruducts. Sugar combines with oxygen inside the living cells and produce some output, under a slow rate. This process is called as respiration. It releases the 'energy in the form of complex molecules for use in maintaining the cell functions. Plants are engaged in both photosynthesis and respiration. Animals can not make their own food. They must eat other organisms to obtain the energy rich molecules for survival. Therefore, they are the major consumers. Animals are technically called as heterotrophs ( other - nourishing ).

Food Chains and Food Webs A food chain is a linear network of links in a food web starting from producer organisms such as grass or trees which use radiation from the Sun to make their food and ending at apex predator species like grizzly bears or killer whales, detritivores like earthworms or woodlice, or decomposer species such as fungi or bacteria. A food chain also shows how the organisms are related with each other by the food they eat. Each level of a food chain represents a different trophic level. Food chains were first introduced by the Arab scientist and philosopher Al-Jahiz in the 10th century and later popularized in a book published in 1927 by Charles Elton, There are two types of food chains: the grazing food chain, beginning with autotrophs, and the detrital food chain, beginning with dead organic matter

Grazing Food C

Detritus Food Chain

Food Web A food web is the natural interconnection of food chains and a graphical representation of whateats-what in an ecological community.

Many food webs have a keystone species. A keystone species is a species that has a large impact on the surrounding environment and can directly affect the food chain. If this keystone species dies off it can set the entire food chain off balance. Keystone species keep herbivores from depleting all of the foliage in their environment and preventing a mass extinction.

Ecological pyramids An ecological pyramid is a graphical representation designed to show the biomass or bioproductivity at each trophic level in a given ecosystem. In an ecological pyramid, the first trophic level forms the base and successive trophic levels the tiers which make up the apex. Ecological pyramids are of three types: (1) Pyramid of numbersIt represents the numerical relationship between different trophic levels of a food chain. In such a pyramid, the more abundant species form the base of pyramid and the less abundant species remain near the top. The pyramid of numbers can be best understood by taking lake or grassland as an example. (2) Pyramid of Biomass-

The biomass i.e. the living weight of the organisms of the food chain present at any time in an ecosystem forms the pyramid of biomass. The pyramid of biomass indicates the decrease or the gradual reduction in biomass at each trophic level from base to apex. (3) Pyramid of energyIt indicates the total energy at each trophic level of the food chain. It also exhibits that at each trophic level loss of energy and material takes place as the processes of assimilation and growth are not 100 per-cent efficient.

Thus at the producer level, the total energy available is more than at the higher trophic levels because of the loss of energy from one trophic level to the other. This means that the organic matter produced per average unit of time, and the energy represented by it, becomes less at each trophic level. The production rate of energy at different trophic levels of an ecosystem can be represented by the pyramid of energy. The base of such a pyramid is represented by the autotrophs i.e. green plants and the higher levels are represented by different herbivore and carnivore trophic levels. Habitat destruction: A forest is a living world for organisms and plants. Due to some events, a change in the setup may occur which will ultimately affect the ecosystem. For example, cutting the trees in a forest is considered to be a habitat destrcution: This activity a) destroys the homes of some animals, b) increases the amount of light that reaches the forest floor, c) reduces the amount of food for organisms that depend on those trees, d) reduces the amount of carbon dioxide taken from the air and oxygen released into it. As a result of this habitat destruction, some organisms may become threatened, endangered and eventually extinct. Hence, it is necessary to preserve the ecosystems.

Ecological Succession Ecological succession is the term used to describe what happens to an ecological community over time. It refers to more or less predictable and orderly set of changes that happen in the composition or structure of ecological community. When you are born, your learn to crawl, then walk and then run. When you grow old, your body goes through certain predictable changes over a period of time as in your body grows taller, your hair grows longer, your mind and body develops. Similarly, when you plant a tree, it grows slowly and then grows bigger and bigger and bigger. Basically, its a predictable set of changes that are visible over a period of time. The time scale can be decades or even millions of years. It is different from Ecological Evolution because the changes that occur aren’t evolutionary in nature, but they may be adaptive. It is based on the principle and knowledge that nothing in life ever remains the same, but that all habitats are in a process of constant change as a result of the inter-dependencies and reactions within the ecological system itself.

Types of Ecological Succession Succession may be initiated either by formation of new habitat (landslide or lava flow) or disturbance of already existing habitat (fires, land clearance). There are three recognized stages to ecological succession. Each covers a gradual process of change and development. They do not have hard and defined boundaries, and it is possibly for an ecological system to be in both stages at once during the transition period from one to another. The 3 stages of ecological succession are: 1. Primary – This is when an ecological community first enters into a new form of habitat that it has not been present in before. A good example of this would be the habitat created when granite is removed in a quarry. The rock face that is left behind is altered and becomes a new habitat. The environment that then grows within that habitat is considered to be in its primary stage. 2. Secondary – The secondary succession stage occurs after a habitat has been established, but it is then disturbed or changed in some fashion and a new community moves in. To use the example from before – let us say that a primary stage develops on the face of a newly quarried granite cliff. That habitat grows undisturbed, until there is a forest fire that then burns and changes a portion of the habitat that has been growing on the rock face. That ecological habitat has now entered its secondary stage. 3. Climax – the climax stage is the last stage of an ecosystem. It is when the ecosystem has become balanced and there is little risk of an interfering event or change to mutate the environment. Several rainforests and deserts qualify as being in the climax stage. What is tricky

about a climax stage is that given human development, any ecosystem that is in the climax stage now holds the risk of being destroyed and going backward in the stages.

Stages of Ecological Succession When talking about the types of ecological succession it is important to remember that the “types” occur within the stages, but they may not necessarily be unique to that stage. What determines the stage that an ecosystem is in is dependent on its energy balance – which is discussed in the next section. There are four main type...