- 1 What is Ecosystem and Define Components of Ecosystem
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What is Ecosystem and Define Components of Ecosystem
The physical and biological world where we live is called our environment. The environment includes our physical surroundings like air (or atmosphere), water bodies, soil (land) and all the organisms such as plants, animals, human beings and micro-organisms like bacteria and fungi (called decomposers). All these constituents of the environment are dependent on one another. So, all the constituents of environment interact with one another and maintain a balance in the environment in a natural way.
Human beings are the only organisms who change the natural environment to fulfil their needs of food, clothing, housing, transport and industry, etc. In fact, the uncontrolled activities of human beings are damaging the balanced and healthy environment more and more.
Biodegradable and Non-biodegradable Wastes
All the waste materials produced by the various activities of man and animals are poisonous to some extent and Gan be divided into two main groups :
- Biodegradable wastes, and
- Non-biodegradable wastes.
Those waste materials which can be broken down to non-poisonous substances in nature in due
course of time by the action of micro-organisms like certain bacteria, are called biodegradable wastes. A biodegradable waste decays (decomposes) naturally and becomes harmless after some time. Cattle dung and compost are common examples of biodegradable wastes. [Compost is the manure made from decayed vegetable-stuff (plants)]. Other examples of biodegradable materials are: Animal bones ; Leather ; Tea- leaves ; Wool; Paper; Wheat; Wood ; Hay; Cotton; Jute ; Grass ; Fruit and Vegetable peels ; Leaves, Flowers, and Cake, etc. Biodegradable wastes usually do not pollute the environment. Biodegradable wastes pollute the environment only when their amount is large which cannot be degraded (or decomposed) into harmless substances in nature at the right time.
The waste materials which cannot be broken down into non-poisonous or harmless substances in nature are called non-biodegradable wastes. The examples of non-biodegradable wastes are: D.D.T. (Dichloro Diphenyl Trichloroethane); Plastics; Polythene bags; Bail-point pen refill; Synthetic fibres; Glass objects; Metal articles like Aluminium cans; Iron nails; Silver foil and Radioactive wastes. All these non-biodegradable wastes cannot be made less toxic (less poisonous) easily and hence they are major pollutants of the environment. The non-biodegradable wastes cannot be decomposed by micro-organisms like bacteria.
D.D.T. is a non-biodegradable waste so it can be passed along the food chain from crops to man or other animals and birds and harm them. For this reason, D.D.T. has been banned from use in most countries. Non-biodegradable wastes are the major pollutants of the environment. For example, the discarded plastic articles, glass articles and metal objects are the non-biodegradable waste materials which cause a lot of pollution in our surroundings. We will now describe a simple experiment to find out whether a given material is biodegradable or non-biodegradable.
We take a piece of paper, a piece of an old cotton cloth and a plastic bag (polythene bag). Dig the ground to about 15 centimetres depth and place the pieces of paper, cotton cloth and plastic bag in the dug up ground separately. We cover them with soil. Leave these buried materials in the ground for about a month. After a month, we dig up the buried materials and observe them.
We will find that the piece of paper and the piece of cotton cloth have been partially eaten up (or decomposed) but the plastic bag has remained unaffected, it has not been eaten up (or decomposed). This means that paper and cotton cloth have been decomposed by the micro-organisms present in the soil. So, paper and cotton cloth are biodegradable. On the other hand, the plastic bag has not been decomposed by the micro-organisms present in the soil, therefore, plastic is non-biodegradable. So, the decomposer organisms are not able to decompose plastic into simpler harmless substances.
We will now explain why some materials are biodegradable whereas others are non-biodegradable. The micro-organisms like bacteria and other decomposer organisms (called saprophytes) present in our environment are ‘specific’ in their action. They break down the natural materials or products made from natural materials (say, paper) but do not break down man-made materials such as plastics. So, it is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable whereas others are non-biodegradable.
We should use the shopping bags (or carry bags) made of paper, cotton cloth or jute because these are
biodegradable materials. On the other hand, plastic bags (or polythene bags) should be avoided because plastic is a non-biodegradable material.
The various communities of living organisms (plants and animals) interact among themselves as well as with their physical environment like soil, air and water. The living organisms interact with one another through their food chains in which one organism consumes another organism. The living organisms like plants interact with soil to get essential nutrients like nitrogen, phosphorus, etc.; with air to get carbon dioxide and also with water bodies, for carrying out the process of photosynthesis.
Thus, the various communities of living organisms (called biotic communities) like plants and animals alongwith soil, air and water of that region form a self-sustaining or functional unit of the living world. This ‘functional unit’ or ‘system’ made up of living and non-living components which is capable of independent existence is called an ecosystem. The ecosystem includes all the communities of an area (all the plants and animals of an area) functioning with their non-living environment like soil, air and water. We can now define an ecosystem as follows.
An ecosystem is a self-contained unit of living things (plants, animals and decomposers), and their non-living environment (soil, air and water). An ecosystem needs only the input of sunlight energy for its functioning. The examples of ecosystems are : a grassland (meadow); a forest; a desert; a mountain; a
pond; a lake; a river; and sea. When we say that a pond or lake is an ecosystem, then the word pond also includes all the aquatic life (plants and animals) which occurs in this pond water. This is because the living organisms are found everywhere. Similarly, when we say that a forest is an ecosystem then it means the physical environment of the forest like soil, air and water alongwith all the plants and animals which occur in the forest.
The desert, grassland, forest, cropfield and mountains represent terrestrial ecosystems (land- based ecosystems) whereas ponds, lakes, river, sea and aquarium represent aquatic ecosystems (water- based ecosystems). Most of the ecosystems in the world are natural ecosystems but some of them are also man-made ecosystems or artificial ecosystems. The examples of artificial ecosystems are crop-fields (agricultural lands); gardens; parks and aquarium.
Components of an Ecosystem
All the ecosystems are made up of two main components: Abiotic components, and Biotic components. Abiotic components mean non-living components and biotic components mean living components. Thus, we can now say that an ecosystem consists of non-living environment and the living biological community.
1. Abiotic Components of an Ecosystem. The abiotic components of an ecosystem (or the non-living components of an ecosystem) include the physical environment like soil, water and air alongwith the inorganic substances like carbon dioxide, nitrogen, oxygen, water, phosphorus, sulphur, sodium, potassium, calcium and other elements present in them. The physical factors or climatic factors like light, temperature, pressure and humidity are also considered abiotic components of the ecosystem.
2. Biotic Components of an Ecosystem. The biotic component of an ecosystem (or the living component of an ecosystem) is a community of organisms (like plants and animals), which is made up of many different inter-dependent populations. The biotic community (or living community) of an ecosystem includes three types of organisms:
- Producer organisms (or Autotrophs) which synthesize their own food. All the green plants are producers.
- Consumer organisms (or Heterotrophs) which are dependent on others for food. All the animals are consumers.
- Decomposer organisms (or Saprotrophs) which consume the dead remains of other organisms. Certain bacteria and fungi are decomposers.
The Functioning of an Ecosystem
We will now describe how an ecosystem functions as a self-sufficient or independent unit in nature. We have just discussed that an ecosystem has non-living components like soil, water and air which contain inorganic nutrient elements, and the living components called producers, consumers and decomposer organisms. All these components make the ecosystem function as follows: From the nutrient pool of the earth (soil, water and air), carbo dioxide and water are absorbed by the producer organisms (green plants): With the help of sunlight energy, the producer organisms convert these inorganic substances into organic compounds like carbohydrates which act as a food.
Thus, producers trap the solar energy and then provide the basic food or energy for all other life forms in the ecosystem. The consumers (animals) derive their energy needs, directly or indirectly, from producers (plants). When the producers (plants) and consumers (animals) die, then the decomposer organisms act on their dead bodies to return the various elements back to the nutrient pool (soil, water and air). Thus, an ecosystem involves input of energy and matter which are exchanged between living and non-living components in a cyclic process.
Producers, Consumers and Decomposers
According to the manner in which they obtain their food from the environment, all the organisms can be divided into three groups: producers, consumers and decomposers.
Those organisms which produce food are called producers. Producers are the organisms which can prepare their own food from simple inorganic substances like carbon dioxide and water by using sunlight energy in the presence of chlorophyll. The examples of producers are green plants and certain blue-green algae. The green plants synthesize their food during photosynthesis by taking raw materials from the earth and energy from the sun.
The green plants produce carbohydrates by photosynthesis and also synthesize proteins and fats. Thus, the green plants are called producers in the living world. Producers are the autotrophic organisms (self¬feeder organisms) in the ecosystem upon which other organisms depend for food. Thus, producers (like green plants) are autotrophs.
Those organisms which consume food (eat food) prepared by producers are called consumers. The consumers depend on producers for food, directly or indirectly. The consumers get their food by eating other organisms or their products. In most simple words, consumers are the organisms that eat other organisms. All the animals are consumers. Even the microscopic animal life of the water called protozoa are consumer organisms.
The examples of common consumer organisms are man, goat, deer, fish, lion, cow and buffalo, etc. The cow and buffalo eat green grass and other green fodder because green grass and other green plants are producers of food. The bio-mass of grass and plants supplies food and energy to these animals like cow and buffalo. It should be noted that the consumer organisms like animals cannot prepare food from simple inorganic substances through photosynthesis. The consumers need ready-made food for their survival which they get from producers (green plants), either directly or indirectly.
If an animal eats grass or other green plants or their products itself we say that it gets the food from producers directly. For example, a goat gets the food from producers directly when it eats grass. On the other hand, if an animal eats the meat of another animal (which eats grass), then we say that it gets the food from producer indirectly. For example, a lion gets food by eating goat which in turn eats grass. So, in this case the lion gets its food indirectly from producer grass (through Figure the goat). Consumer organisms are also called heterotrophs. are consumers of food. This goat is a consumer which Consumers can be further divided into three groups : herbivores, carnivores and omnivores.
Some animals eat only plants (or their products). Those animals which eat only plants are called herbivores. The herbivores may eat grasses, leaves, grains, fruits or the bark of trees. Sortie of the examples of herbivores are : Cow, Buffalo, Goat, Sheep, Horse, Deer, Camel, Ass, Ox, Elephant, Monkey, Squirrel, Rabbit and Hippopotamus. Cow is called a herbivore because it eats only plants (or plant products) as food.
Herbivores are also known as herbivorous animals. The animals which get their food by eating the producers (plants) directly are called primary consumers. Since herbivores obtain their food directly from plants (or producers), therefore, herbivores (like cattle, deer, goat, etc.) are primary consumers.
Some animals eat only other animals. They do not eat plant food at all. Those animals which eat only other animals as food are called carnivores. The carnivores eat the meat (or flesh) of other animals. So, we can also say that those animals which eat only the meat (or flesh) of other animals are called carnivores. Some of the examples of the carnivores are : Lion, Tiger, Frog, Vulture, Kingfisher, Lizard, Wolf, Snake and Hawk. Lion is called a carnivore because it eats only the meat (or flesh) of other animals like deer, rabbit and goat, etc. Carnivores are also known as carnivorous animals.
The carnivores are usually of two types : small carnivores and large carnivores. The small carnivores which feed on herbivores (primary consumers) are called secondary consumers. For example, a frog, lizard, bird and fox, etc., are secondary consumers. The large carnivores (or top carnivores) which feed upon the small carnivores (secondary consumers) are called tertiary consumers. For example, lion, tiger and birds of prey (such as hawk) are some of the tertiary consumers. Please note that humans (man) can be primary, secondary or tertiary consumers depending on the food which they eat.
Some animals eat both, plants as well as other animals. Those animals which eat both, plants and animals, are called omnivores. In other words, the omnivores eat plant food as well as the meat (or flesh) of other animals. Some of the examples of omnivores are : Man (human beings), Dog, Crow, Sparrow, Bear, Mynah and Ant.
Man is called an omnivore because he eats both, plant food (such as grains, pulses, fruits and vegetables) as well as meat of animals (such as goat, chicken and fish). Omnivores are also called omnivorous animals.
We will now describe another type of producers and consumers which are extremely small. These are called planktons. Planktons are very minute or microscopic organisms freely floating on the surface of water in a pond, lake, river or ocean.
Planktons are of two types : Phytoplanktons and Zooplanktons. The microscopic aquatic plants freely floating on the surface of water are called phytoplanktons. The free-floating algae is an example of phytoplankton. Phytoplanktons are capable of producing food by the process of photosynthesis. The microscopic aquatic animals freely floating on water are called zooplanktons. The freely-floating protozoa are an example of zooplankton. A very, very small fish is also a zooplankton. Planktons float near the surface of water and provide food for many fish and other aquatic animals.
The non-green micro-organisms like some bacteria and fungi, which are incapable of producing their food, live on the dead and decaying (rotting) plants and animal bodies and are consumers of a special type called decomposers. We can now say that: The micro-organisms which break down the complex organic compounds present in dead organisms like dead plants and animals and their products like faeces,
urine, etc., into simpler substances are called decomposers. The examples of decomposers are certain bacteria and fungi. The bacteria which act as decomposers are called putrefying bacteria. The bacteria and fungi act as decomposers by the secretions of their body surfaces which decompose the organic matter present in dead plants and animals into simpler substances and liberate ammonia, carbon dioxide, etc. They absorb some of these simpler substances for their own maintenance and release the remaining into the soil, water and air to be used by the producers again In this way, decomposers help in the recycling of materials in ecosystem. The decomposers are also known as micro-consumers or saprotrophs.
Importance of Decomposers
The decomposers help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment. The decomposers also help in putting back the various elements of which the dead plants and animals are made, back into the soil, air and water for re-use by the producers like crop-plants. This maintains the fertility of soil and the soil Would continue to support crops again and again.
For example, the decomposers like putrefying bacteria and fungi decompose the dead plants and animal bodies into ammonia (and other simpler substances). This ammonia is converted into nitrates by the nitrifying bacteria present in soil. These nitrates act as fertilizer in the soil and are again absorbed by the plants for their growth. Thus, it is only due to the presence of decomposers that the various nutrient elements which were initially taken by plants from the soil, air and water are returned to the soil, air and water, after the death of plants and animals.
If, however, there were no decomposers, then the dead bodies of plants and animals would keep lying as such and the elements of which plant and animal bodies are made, would never be returned to their original pools like soil, air and water. In that case, the cyclic process of life and death would be disrupted.
This is because in the absence of decomposers the soil, air and water would not be replenished by elements from the bodies of dead organisms. All the nutrients present in soil, air and water would soon be exhausted and evolution of life would come to an end. Thus, the decomposer organisms help in recycling the materials in the ecosystem so that the process of life may go on and on like an unending chain.