An ecosystem is a community where all living organisms (like plants, animals, and microorganisms) interact with each other and with the non-living components of their environment, such as temperature, rainfall, and soil. This interaction creates a balanced system in nature.
Every ecosystem has two main types of components:
Biotic Components: These are all the living organisms in an ecosystem. This includes producers, consumers, and decomposers.
Abiotic Components: These are the non-living physical factors that affect the living organisms. Examples include temperature, rainfall, wind, soil, and minerals.
Example
A garden is a great example of an ecosystem. It has biotic components like grasses, trees, flowers (roses, jasmine), and animals (frogs, insects, birds). These living things interact with each other and are affected by abiotic components like sunlight, water, and soil.
Ecosystems can be categorized into two types:
Natural Ecosystems: These exist in nature without human intervention. Examples are forests, ponds, and lakes.
Artificial Ecosystems: These are created and maintained by humans. Examples include gardens, crop-fields, and aquariums.
Roles of Organisms in an Ecosystem
Organisms are grouped based on how they get their food or sustenance.
Producers
Producers are organisms that can create their own food from simple inorganic substances. They use the sun's radiant energy to make organic compounds like sugar and starch through photosynthesis.
All green plants and certain bacteria are producers.
They are also called autotrophs.
Consumers
Consumers are organisms that get their energy by eating other organisms. They depend on producers, either directly or indirectly.
They are also called heterotrophs.
Consumers can be classified into several groups:
Herbivores: Animals that eat only plants (e.g., goat, deer).
Carnivores: Animals that eat other animals (e.g., tiger, snake).
Omnivores: Animals that eat both plants and animals (e.g., human, bear).
Parasites: Organisms that live on or inside another organism (the host) and get their food from it (e.g., lice, tapeworms).
Decomposers
Decomposers are microorganisms that break down the dead remains and waste products of other organisms.
This group mainly consists of bacteria and fungi.
They convert complex organic substances into simple inorganic substances that are returned to the soil.
This process is crucial for the natural replenishment of the soil, as it makes nutrients available for plants to use again. Without decomposers, dead organisms and garbage would pile up, and the nutrients locked within them would not be recycled.
Food Chains and Webs
The interactions between organisms in an ecosystem involve the flow of energy from one to another. This flow can be represented through food chains and food webs.
Food Chains
A food chain is a sequence of organisms where each one feeds on the one below it in the series. It shows how energy is transferred from one living organism to another.
Each step in a food chain is called a trophic level.
First Trophic Level: Producers (autotrophs) that capture solar energy.
Second Trophic Level: Primary Consumers (herbivores) that eat producers.
Third Trophic Level: Secondary Consumers (small carnivores) that eat primary consumers.
Pond Food Chain: Algae → Small aquatic insects → Fish → Bird
Energy Flow in an Ecosystem
Energy flows through the different trophic levels in a specific way.
Unidirectional Flow: The flow of energy is one-way. Energy captured by producers from the sun does not go back to the sun. Similarly, energy that passes to herbivores does not return to the producers.
Energy Loss at Each Level: When one form of energy is changed to another, some energy is lost to the environment as heat that cannot be reused.
Plants capture only about 1% of the sunlight that falls on their leaves and convert it into food energy.
10% Law: When an organism is eaten, only about 10% of its energy is stored in the body of the consumer and becomes available for the next trophic level. The rest is lost as heat, used for life processes like digestion and movement, or goes towards growth and reproduction.
Note
Because so much energy is lost at each step, food chains are generally limited to only three or four trophic levels. There is not enough usable energy left to support organisms at higher levels. This also explains why there are a greater number of individuals at the lower trophic levels, with the largest number being the producers.
Food Web
In most ecosystems, the feeding relationships are more complex than a simple straight line. An organism is often eaten by two or more other kinds of organisms, which in turn are eaten by several others. This network of many interconnected food chains is called a food web. (See Figure 13.3)
Biological Magnification
Harmful, non-degradable chemicals like pesticides can enter the food chain.
These chemicals are washed from fields into soil or water bodies.
Plants absorb them from the soil, and aquatic organisms take them up from the water.
Since these chemicals cannot be broken down, they accumulate in an organism's body.
At each trophic level, the concentration of these chemicals increases.
Biological magnification is the phenomenon where the concentration of harmful chemicals increases at each successive trophic level in a food chain.
Since humans are often at the top of the food chain, the maximum concentration of these chemicals gets accumulated in our bodies. This is why our food (grains, fruits, vegetables, and meat) can contain pesticide residues.
HOW DO OUR ACTIVITIES AFFECT THE ENVIRONMENT?
Human activities have a significant impact on the environment, often leading to problems like pollution. Two major environmental problems are the depletion of the ozone layer and the challenge of waste disposal.
Ozone Layer and How it is Getting Depleted
Ozone (O3) is a molecule made of three oxygen atoms. While the oxygen we breathe is O2, ozone is a deadly poison at ground level. However, high up in the atmosphere, it performs a vital function.
The ozone layer is a shield in the upper atmosphere that protects the Earth's surface from most of the Sun's harmful ultraviolet (UV) radiation. This radiation is very damaging to living organisms and is known to cause skin cancer in humans.
Formation of Ozone
Ozone is formed in the atmosphere through a natural process involving UV radiation and oxygen.
High-energy UV radiation from the sun splits some molecular oxygen (O2) into free oxygen atoms (O).
O2UVO+O
These free oxygen atoms then combine with other molecular oxygen (O2) to form ozone (O3).
O+O2→O3
Depletion of the Ozone Layer
In the 1980s, scientists discovered that the amount of ozone in the atmosphere was dropping sharply. This depletion was linked to synthetic chemicals, particularly chlorofluorocarbons (CFCs).
CFCs were widely used as refrigerants and in fire extinguishers.
In 1987, the United Nations Environment Programme (UNEP) successfully created an international agreement (the Montreal Protocol) to freeze CFC production at 1986 levels.
It is now mandatory for manufacturing companies worldwide to produce CFC-free refrigerators.
Managing the Garbage we Produce
Our daily activities generate a large amount of waste material, or garbage. These waste materials can be classified into two main types based on how they break down.
Biodegradable and Non-biodegradable Substances
The enzymes in our bodies are specific; they can break down the food we eat but not everything. Similarly, microorganisms like bacteria have specific enzymes that can break down some materials but not others.
Biodegradable Substances: These are substances that can be broken down into simpler compounds by the action of microorganisms (biological processes). Examples include kitchen waste (vegetable peels, spoilt food), paper, and cotton clothes.
Non-biodegradable Substances: These are substances that cannot be broken down by microorganisms. They can persist in the environment for a very long time and may harm the ecosystem. Many human-made materials, like plastics, are non-biodegradable. They can be acted upon by physical processes like heat and pressure but do not decompose naturally under normal conditions.
Waste Management
Improvements in our lifestyle, changes in attitude (using more disposable items), and modern packaging have led to a massive increase in the amount of non-biodegradable waste we generate. This creates serious environmental problems.
Example
Disposable cups in trains
Originally, tea was served in plastic glasses that were returned and reused. Then, disposable plastic cups were introduced for hygiene, but this created a huge waste problem. As an alternative, clay cups (kulhads) were suggested, but making them on a large scale would lead to the loss of fertile topsoil. Now, disposable paper cups are often used, which are a better alternative to plastic as they are biodegradable.
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