Ecosystems PDF
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This document introduces the fundamental concepts of ecosystems, including biotic and abiotic components, producers, and consumers. It explains the interactions within ecosystems through examples of food chains and food webs, and highlights the importance of forests.
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# Ecosystems ## Key Concepts - Ecosystem - Biotic components - Interdependence between organisms - Food chain, food web and pyramid of numbers - Abiotic components - Interdependence between organisms: symbiosis, parasitism and predation - Forest ecosystem with its flora and fauna ## The Environmen...
# Ecosystems ## Key Concepts - Ecosystem - Biotic components - Interdependence between organisms - Food chain, food web and pyramid of numbers - Abiotic components - Interdependence between organisms: symbiosis, parasitism and predation - Forest ecosystem with its flora and fauna ## The Environment The word 'environment' refers to the variety of living and non-living things present around an organism. Everything that surrounds and affects the life of an organism forms its environment. A lion in a forest is an example of an organism in its environment. A forest has innumerable other living things too, such insects, other animals and plants. It also has non-living things such as air, water, soil and minerals. There is also a cultural component in the environment, which includes the impact of human activities on it. All the activities of an organism are influenced by its environment. ## Ecosystem and its Components All living organisms need food and other materials from their surroundings. The life of an organism is affected by the living and non-living components around it. All living organisms can be categorized into three groups: - **Producers**: Green plants that make their own food by using sunlight, water and carbon dioxide. - **Consumers**: Animals that eat plants and other animals (also called heterotrophs). - **Decomposers**: Fungi, bacteria and worms that feed on dead organisms and decompose them into simple nutrients that are returned to the soil for use by plants. They clean up the environment. <br/> ***Diagram: Biotic and abiotic components of the environment*** | NON-LIVING (ABIOTIC) COMPONENTS | |---|---| | SUNLIGHT: source of energy for life on earth | | SOIL: medium for growth of plants | | WATER: necessary for life processes | <br/> ## Components of an Ecosystem An ecosystem has two main components: - **Biotic**: Plants, animals and microorganisms. - **Abiotic**: Air, water, soil and climate factors such as sunlight, temperature, humidity and wind. ## Biotic Components - **Producers**: All living organisms need energy for their survival. The ultimate source of energy on earth is solar energy. Only green plants have the ability to use this solar energy. Green plants make their own food in the presence of sunlight using water, minerals and carbon dioxide. Thus, green plants are called producers or autotrophs. - **Consumers**: Living organisms that cannot make their own food but consume either plants or other animals, are called consumers or heterotrophs. All animals are consumers. They are further divided into: - **Herbivores**: Animals that eat green plants are called herbivores or primary consumers, for example, deer, horse, elephant and so on. - **Carnivores**: Animals that eat other living animals are called carnivores or secondary consumers, for example, tiger, lion, leopard and so on. - **Omnivores**: Some animals that eat both plants and other animals are called omnivores, for example, human beings, crow, cockroach, bear and so on. - **Scavengers**: Some carnivores that feed on dead animals are called scavengers, for example, hyena, vulture and jackal. - **Decomposers**: In addition to producers and consumers, there are some microscopic organisms that feed on the dead bodies of organisms and decaying organic matter. They are called decomposers, for example, certain bacteria and fungi. Decomposers break down the complex organic compounds present in the remains of dead plants and animals into simpler substances. They are useful in releasing nutrients from dead, decaying organisms back into the environment. These nutrients are reused by plants. Thus, decomposers help in the recycling of nutrients. Decomposers are also called nature's scavengers. ## Interactions within Biotic Components Biotic components are linked to each other primarily by food and form food chains and food webs. - **Food Chain**: A series of organisms that are linked to each other through a process of eating and being eaten form a food chain. For example, in a typical food chain, the plants (producers) are eaten by a rabbit (primary consumer). The rabbit is eaten by a snake (secondary consumer), which in turn is eaten by an eagle (tertiary consumer). When the eagle dies, its body is decomposed by microorganisms such as fungi and bacteria into simpler nutrients, which are returned to the soil for reuse by plants. Thus, a chain of eating and being eaten is formed. - **Food Web**: Most consumers have more than one source of food. For example, Frogs eat caterpillars besides grasshoppers. Snakes eat rabbits as well as lizards, mice and rats. Rats are also eaten by hawks. Thus, a plant or animal may be a part of several food chains. Several food chains are interconnected to form a food web. ## Flow of Energy As only green plants (producers) can trap energy from the sun, all food chains start with plants. Solar energy is transferred through food chains. - **Unidirectional flow of energy**: The flow of energy from producers to consumers is always in one direction. Only 10 per cent of the energy stored by producers is passed on to primary consumers. A secondary consumer who eats the primary consumer absorbs only 10 per cent of its energy. Therefore, most food chains never go higher than secondary or tertiary consumers. ## Trophic Levels and Pyramid of Numbers The various steps representing organisms in a food chain at which transfer of food and energy takes place are called trophic levels. - **First trophic level**: Green plants or producers, that fix the solar energy constitute the first trophic level. - **Second trophic level**: Herbivores or primary consumers constitute the second trophic level, for example, snails, rabbit, deer and goat. - **Third trophic level**: Carnivores or secondary consumers that feed on herbivores constitute the third trophic level, for example, snakes, frogs, small birds and small fish. - **Fourth trophic level**: Large carnivores (top carnivores) or tertiary consumers that feed on the small carnivores constitute the fourth trophic level, for example, eagle, tiger and lion. ## Abiotic Components Non-living things in the environment are called its abiotic components. Abiotic components include air, water, soil and climatic factors such as sunlight, temperature, humidity and wind. Each of these has a specific influence on the life processes of various organisms. - **Air**: All living organisms on earth need air to live. Green plants use carbon dioxide from the air to make food and give out oxygen. This oxygen is used by living organisms for respiration. - **Water**: Water is extremely important for all living organisms. All metabolic activities such as digestion, excretion and circulation occur with water as the medium. Green plants need water to prepare food. Water is also the main constituent of all living organisms. For example, the human body consists of 60 to 70 per cent of water by weight. The amount of water and rainfall in a region affects the kind of plants and animals found there. For example, desert regions where there is scarcity of water have less vegetation; whereas the Western Ghats and Assam that receive heavy rainfall have dense evergreen forests. Water in rivers, lakes, ponds and oceans is also home to many living organisms. - **Soil**: Soil is the topmost layer of the earth's crust. All life on earth depends on the soil, because it provides a medium for the growth of plants. Plants growing on land get water and minerals from the soil. Soil is also home to a variety of living organisms such as bacteria, fungi, worms and insects. These organisms keep adding minerals and nutrients to the soil and enrich it. - **Climatic Factors**: The sun is the primary source of light and energy on earth. It affects plant and animal activities in a number of ways. For example, green plants make food in the presence of sunlight, light influences the closing and opening of stomata, germination of seeds, and so on. The amount of sunlight in a particular area has a direct influence on the types of plants and animals found there.. ## Forest Ecosystem Forests are one of the largest and the most complex ecosystems. Forests occupy about one-third of the land on earth. They are a rich source of biodiversity. About one-fifth of the total land area is occupied by forests in India. Forests can be of several types: - **Temperate or tropical forest**: Depending on temperature. - **Wet or dry forest**: Depending on rainfall. - **Evergreen or deciduous forest**: Depending on occurrence of flora. ## Components of a Forest Ecosystem Like other ecosystems, a forest ecosystem has both biotic and abiotic components. - **Biotic Components**: The biotic components of a forest include producers, consumers and decomposers. The producers are mainly herbs, shrubs and trees. A wide variety of grasses, ferns, creepers, berries, herbs and shrubs are found in a forest ecosystem. The trees in a forest are home to thousands of birds and animals. The consumers include herbivores, carnivores as well as omnivores. Herbivores such as deer, nilgai and elephants feed on grasses or shrubs. Leaf hoppers, bugs, beetles and so on, feed on grasses and leaves of trees. Carnivores such as tigers, lions and foxes consume their prey largely by predation. There are also a large number of predatory birds such as eagle and kite. Decomposers include bacteria and fungi. They derive their nutrition from dead and decaying organisms, which include both plants (especially leaves fallen on the forest floor) and animals. - **Abiotic Components**: The abiotic components of a forest ecosystem include air rich in oxygen, water contained in several water bodies and organic and inorganic compounds in trees and soil as well as in the dead remains of plants and animals. Climatic factors such as sunlight, temperature, rainfall and humidity play a great role in determining the flora and fauna in a forest ecosystem. In temperate forests, the climate changes a lot from summer to winter. In tropical forests, the climate remains constant throughout the year. Water keeps on circulating in a forest ecosystem. ## Importance of Forests - Forests are a storehouse of biodiversity and biological resources. - They help regulate the climate and atmosphere. - They absorb carbon dioxide and release oxygen. - They play an important role in maintaining the water cycle and bringing rains. - They prevent soil erosion and reduce floods. - They provide timber, fuel, fodder, medicines, and so on. - They help in reducing global warming. ## Difference between Environment and Ecosystem An environment refers to the surroundings of a living organism, while an ecosystem is a community of both living and non-living things that interact with each other.