Why Are There So Many Different Plants and Animals?

Biodiversity refers to the wide variety of living organisms—plants, animals, and microorganisms—found in a particular area or on the entire Earth. In Class 6 Science, you learn that the world around us is filled with many different types of living things, each with unique shapes, sizes, and features. This variety is what we call biodiversity. The term flora is used for all the plants in a region, while fauna refers to all the animals found there. For example, the flora of a forest includes trees like neem and bamboo, while its fauna includes animals like deer and tigers. Biodiversity is important because it helps keep nature balanced; different plants and animals depend on each other for food, shelter, and survival. Many students think only rare or unusual species count as biodiversity, but even common grass and sparrows are part of it.

Living things (biotic components) like plants, animals, and microorganisms interact closely with non-living things (abiotic components) such as water, air, soil, sunlight, and temperature in their habitat. A habitat is the natural home or environment where an organism lives. Biotic components rely on abiotic factors for survival—plants need sunlight, water, and soil to grow, while animals need air and water to live. In turn, living things can change their environment; for example, plants release oxygen into the air, and animals add nutrients to the soil through their waste. For example, in a pond habitat, fish (biotic) need clean water (abiotic) to survive, and plants in the pond provide oxygen for the fish. Some students mistakenly think only living things affect each other, but abiotic factors like temperature and rainfall can also change which organisms can live in a place.

Terrestrial habitats are found on land, such as forests, grasslands, deserts, and mountains, while aquatic habitats are found in water, like ponds, lakes, rivers, and seas. Terrestrial habitats differ in soil type, amount of water, and temperature. For example, deserts have sandy soil, very little water, and high temperatures, while forests have rich soil, plenty of water, and moderate temperatures. Aquatic habitats are mainly defined by the type and amount of water (fresh or salty), temperature, and how much sunlight reaches the water. For example, a pond has still, fresh water and supports plants like lotus and animals like frogs, while the sea has salty water and supports fish like hilsa and plants like seaweed. Many students think all water habitats are similar, but a river and a sea are very different in water movement, salt content, and the types of organisms found.

Adaptations are special features or habits that help living things survive in their specific habitats. These can be changes in body structure, behaviour, or way of living. For example, a camel has long legs, thick lips, and a hump to store fat, which help it survive in the hot, dry desert. Fish have gills to breathe underwater and fins to swim easily. Frogs can live both in water and on land because they have webbed feet for swimming and lungs for breathing air. Mountain trees like pine have needle-shaped leaves and sloping branches so that snow slides off easily. In real life, you might notice that cactus plants have thick stems to store water and spines instead of leaves to reduce water loss in deserts. A common mistake is to think that all animals in a habitat have the same adaptations, but each species has its own unique features suited to its environment.