Ecosystems Class 8 Science Notes Maharashtra State Board
Ecosystem:
The world around us is made up of living and non-living factors. The living is called biotic factors while non-living are called abiotic factors. There is a continuous interaction between these living and non-living factors. Living organisms and their habitat, and environment are correlated with each other. The structure which is formed due to these reciprocal relationships is called an ecosystem. Biotic and abiotic factors and their interactions form an ecosystem.
The organic substances (carbohydrates, proteins, and lipids) from dead bodies of plants and animals are converted into inorganic substances (hydrogen, oxygen, calcium, iron, sodium, potassium, etc.) by microorganisms. Therefore, microbes are said to be ‘Decomposers’.
Structure of an Ecosystem:
Living organisms need different types of abiotic factors and they have different capacities to adapt to those abiotic factors. Some microbes need oxygen, while others don’t. Some plants need more sunlight, while others grow well in shade. Every abiotic factor (air, water, soil, sunlight, temperature, humidity) affects the biotic factors in the ecosystem. The abiotic factors in an ecosystem decide which biotic factors will survive in it and what will be their number. The proportion of abiotic factors in an ecosystem is always changing as biotic factors use or excrete abiotic factors. Every biotic factor affects abiotic factors as well as other biotic factors around it. Every living organism in an ecosystem plays a particular role while living, and moving in that ecosystem.
The position of any living organism in context to other living organisms and the role it is playing is called ‘Niche’.
Eg. A sunflower plant in a garden evolves oxygen in the air and provides food and shelter for insects like ants, honeybees, etc.
Most of the ecosystems are complex and there is tremendous quantitative and qualitative variety of species in them. In ecosystems of tropical countries like India, few species of living organisms are found everywhere in a large number. The remaining species of plants and animals are found in a small number. Some species are very few. A variety of ecosystems is found on Earth. Each place has a different ecosystem. eg. Forest, pond, ocean, river, etc. Types of ecosystems are formed according to size, place, climate, and types of plants and animals.
Many types of ecosystems are found in the biosphere. Their specific functions continue according to their environment. Though these ecosystems look independent and different they are linked to each other directly or indirectly. Therefore we can not separate these small ecosystems from each other but can classify them according to their functions. In some regions on Earth, a large area has the same climate and abiotic factors. The living organisms in that area are also similar. So a specific ecosystem develops in a vast area. Such large ecosystems are called ‘Biomes’. These biomes contain many small ecosystems. Earth itself is a vast ecosystem. Two types of biomes are found on the earth.
- Land biomes
- Aquatic Biomes
Land Biomes:
The biomes which exist only on land are called land biomes. Due to unequal distribution of abiotic factors different types of ecosystems exist.
Eg. Grasslands, evergreen forests, deserts, island ecosystems, ecosystems in Taiga, tropical rainforests, etc.
a. Grassland Ecosystem:
Grasslands develop where rainfall is not enough to grow big trees. Vast growth of grass is found in these ecosystems. Longer summers and limited rain develop dwarf plants in these areas. Animals like goats, sheep, giraffe, zebra, elephant, deer, chital, tiger, lion, etc. are found in this ecosystem. Similarly, various birds, insects, and microbes are also present.
About 150 years ago, the Dudhwa forest was the habitat for single-horned rhinos. But in the 20th century, this animal became extinct due to unrelenting hunting. On 1st April 1984, this rhino was restored there. They were bred in captivity and then released into their habitat. For this 27 square km of grassland and forest where round the year water sources were available were selected. Two observatories were established. These efforts are successful.
b. Evergreen Forests:
It’s a natural ecosystem where a variety of plants, animals, and abiotic factors are found.
- Many ecosystems are conserved in around 520 sanctuaries and national parks in India.
- The Great Himalayan National Park is the largest sanctuary where the white panther, a rare species is conserved.
- Elephants, wild bears, wild buffaloes, deer, tigers, and panthers are conserved at Kaziranga (Asam).
- Two third of the total number of single-horned rhinos in the world is found at Kaziranga.
- The sanctuary at Bharatpur is famous for aquatic birds.
- Ranthambore Sanctuary is famous for tigers.
- Geer forest in Gujrat is the only habitat/shelter for the spectacular Asiatic lion.
Aquatic Ecosystems:
71% of the earth’s surface is covered by water and only 29% has land on it. Therefore study of aquatic biomes becomes very important. According to the area, aquatic biomes are widespread. Types of aquatic ecosystems are Freshwater ecosystems, marine ecosystems, and creek ecosystems.
A. Fresh Water Ecosystem:
Ponds, lakes, and rivers are included in aquatic ecosystems. The transition of energy in these ecosystems is through water currents and rivers. Decomposers are at the bottom of water reservoirs. They decompose dead bodies of plants and animals and convert them into abiotic factors.
B. Marine Ecosystems:
Marine plants grow in these ecosystems. Shallow water contains small fishes, and prawns feeding on algae. The central part of the sea has less number of aquatic living organisms. Large fishes are secondary consumers. The ocean has a large amount of nutrients. The bottom of oceans has more number of decomposers. Dead bodies of plants animals, and waste materials are decomposed by bacteria.
Diminishment of Ecosystem Due to Human Interference:
Many human activities have side effects on the functions of ecosystems and cause their diminishment.
Eg. mining and excessive cutting of trees change the use of land, so interactions between biotic and abiotic factors are also affected. Different human activities have different effects on ecosystems. They can be the transformation of an ecosystem from one to another or the extinction of a species.
Human Activities Responsible for the Diminishment of Ecosystems
Increasing use of Resources due to increased Population:
Humans are the consumers in an ecosystem. Ecosystems can provide basic needs in normal conditions, but due to increased population, man kept on snatching natural resources on a large scale. Changing lifestyle demands ‘more’ than ‘necessary’. That has increased stress on the ecosystems and has generated vast amounts of waste.
Urbanization:
Due to the continuous process of urbanization. More and more agricultural lands, marshlands, wetlands, forests, and grasslands are being destroyed for buildings and other basic facilities around. As a result of this human interference, ecosystems either change or get destroyed.
Industrialization and Traffic:
Raw materials required for industrialization are obtained by destroying forests. This results in the destruction of forests. To provide the amenities for increased traffic, many times roads and railways are built through forests and wetlands.
Tourism:
People visit scenic places mainly for nature watch, entertainment, and a visit to sacred places. A lot of amenities are created for these tourists. This destroys local ecosystems due to increased stress.
Large Dams:
Dams cover vast lands. So the forests or grassland in that area get converted into aquatic ecosystems. Dams also lessen the water current in lower areas. Therefore the previous ecosystems in that running water get destroyed.
Wars:
Differences and competition over land, water, mineral resources, or some economic and political reasons lead to war among human races. Heavy bombing and mine explosions are done in wars. These are not only life-threatening but also change or destroy natural ecosystems. Thus natural disasters (earthquakes, volcanoes, floods, droughts) and human interferences result in changes/destruction of ecosystems. Natural ecosystems must be protected as they maintain balance in the biosphere.
Good Maharashtra State Board Class 8 Science Notes Ecosystems can simplify complex concepts and make studying more efficient.