Diversity in the Living World
The Variety of Plants and Animals
Look around and you will find an amazing variety of living things — tall trees and tiny mosses, soaring eagles and crawling ants, fish in water and camels in the desert. This huge variety of living organisms is called biodiversity.
Even within one group, living things differ from one another. Plants, for example, come in different forms:
- Herbs — small plants with soft, green stems (mint, coriander, grass).
- Shrubs — medium, bushy plants with woody stems branching near the ground (rose, hibiscus).
- Trees — tall, big plants with a thick, woody main stem called a trunk (mango, neem).
- Climbers and creepers — plants with weak stems; climbers rise with support, creepers spread along the ground (money plant; pumpkin).
Animals also vary in where they live, what they eat and how they move. Some live on land, some in water, some can fly. Based on food, animals may be herbivores (plant-eaters, like cows), carnivores (meat-eaters, like lions) or omnivores (eat both, like humans and bears). This rich variety is found everywhere — even a small garden is home to dozens of different living things.
Sort by size and the type of stem.
- Mint — small, soft stem → herb.
- Rose — bushy, woody near the ground → shrub.
- Mango — tall, thick trunk → tree.
Group animals by what they eat.
- An animal that eats only plants is a herbivore.
There is a special word for the variety of life.
- The variety of living organisms is called biodiversity.
Key Points
- The huge variety of living organisms is called biodiversity.
- Plants include herbs, shrubs, trees, climbers and creepers, differing in size and stem.
- By food, animals are herbivores, carnivores or omnivores.
- Living things vary in where they live, what they eat and how they move.
Grouping and Classification of Organisms
Because there are millions of kinds of living things, scientists group them to study them more easily. Putting organisms with similar features together is called classification. We classify by looking at shared characteristics — such as where an organism lives, how it moves, what its body is like, or how it gets food.
A first, simple division is into plants and animals:
- Plants — usually green, fixed in one place, make their own food, and grow throughout life.
- Animals — can usually move from place to place, cannot make their own food (they eat plants or other animals), and most stop growing after a certain stage.
Animals can be grouped further. A useful grouping is by whether they have a backbone:
- Vertebrates — animals that have a backbone (fish, frogs, snakes, birds, cats, humans).
- Invertebrates — animals without a backbone (ants, worms, spiders, snails, jellyfish).
Classification is helpful because it lets us see how living things are similar and different, makes them easier to identify and study, and shows how life on Earth is connected.
Compare a key feature.
- Most plants make their own food and stay fixed in one place.
- Most animals cannot make their own food and can move about.
Check for a backbone.
- Frog and fish have a backbone → vertebrates.
- Ant and earthworm have no backbone → invertebrates.
Classification organises a huge variety of organisms.
- It makes them easier to identify and study.
- It shows how organisms are similar, different and connected.
Key Points
- Classification = grouping organisms by shared characteristics.
- A first split is plants (make food, fixed) vs animals (eat food, can move).
- Animals can be vertebrates (with backbone) or invertebrates (without backbone).
- Classification helps us identify, study and connect living things.
Habitats and Environmental Interactions
The place where a plant or animal naturally lives is called its habitat. A habitat provides an organism with everything it needs — food, water, air, shelter and a place to reproduce. A forest, a pond, a desert and the sea are all habitats.
Habitats are of two broad kinds:
- Terrestrial habitats — on land (forests, grasslands, deserts, mountains).
- Aquatic habitats — in water (ponds, rivers, lakes, oceans).
Every habitat has two kinds of parts. The living (biotic) parts are the plants, animals and other organisms. The non-living (abiotic) parts are things like sunlight, water, air, soil and temperature. The living and non-living parts constantly affect one another — this is an environmental interaction. For instance, the amount of water and sunlight (non-living) decides which plants can grow, and those plants (living) provide food and shelter for animals.
Organisms have special features, called adaptations, that suit them to their habitat. A fish has gills and fins to live in water; a camel has long legs and stores fat in its hump to survive the hot desert; a cactus stores water in its thick stem. An organism removed from its habitat may not survive, which is why protecting habitats is so important.
Habitats have biotic (living) and abiotic (non-living) parts.
- Living part: fish (or water plants, frogs).
- Non-living part: water (or sunlight, air).
Adaptations suit an organism to its habitat.
- It stores fat in its hump to last without food.
- Long legs keep its body away from the hot sand and it can go long without water.
An organism depends on its habitat to meet its needs.
- A fish breathes using gills, which work only in water.
- Out of water it cannot get oxygen, so it cannot survive.
Key Points
- A habitat is the natural home of an organism, giving it food, water, air and shelter.
- Habitats are terrestrial (land) or aquatic (water).
- Each habitat has living (biotic) and non-living (abiotic) parts that interact.
- Adaptations are special features that suit an organism to its habitat.