2.Diversity in the Living World Class 6 Notes | NCERT Science
Class 6 Science Notes: Diversity in the Living World (New NCERT)
Step outside your house and look around for a minute. You'll probably spot a few ants near a wall, a sparrow on a wire, some grass pushing through a crack in the pavement, maybe a stray cat, and a neem or mango tree somewhere close by. None of these look alike, none of them behave the same way, yet all of them are alive. This huge variety of living things around us — different in size, shape, colour, habitat and habits — is what this chapter calls diversity in the living world.
This topic is really about training yourself to notice differences and similarities among organisms, and then understanding why scientists group them the way they do.
What Do We Mean by "Living World"?
The living world includes every organism that is alive — from the tiniest bacteria you can't see with your eyes to massive whales in the ocean. It's easy to assume "living things" just means humans, animals, and plants, but the actual living world is far bigger and stranger than that. It includes fungi like mushrooms, microscopic organisms in a drop of pond water, and even things like moss growing on a damp wall.
What's interesting is that no two organisms — not even two leaves from the same tree — are exactly identical. Slight differences exist everywhere in nature, and this is part of why diversity is such a natural feature of life on Earth.
Why Is There So Much Diversity?
There isn't one single environment on Earth — there are deserts, oceans, mountains, forests, rivers, and icy poles, and each of these places puts different demands on the organisms living there. A fish needs gills to breathe underwater; a camel needs the ability to survive without water for days in a desert. Over long periods of time, organisms develop features that help them survive in their particular surroundings.
So diversity isn't random — it's closely tied to the habitat, or the natural home, of an organism. Different habitats have shaped different kinds of living things, which is why a polar bear looks and behaves nothing like a lizard from the Thar desert.
Characteristics That Help Us Recognise Living Things
Before grouping organisms, it helps to remind ourselves what actually counts as "living." Living organisms generally show these features:
- They can move (even plants move, just slowly — think of a sunflower turning toward the sun)
- They grow in size over time
- They need nutrition (food or nutrients) to survive
- They can reproduce, producing new individuals of their own kind
- They respond to stimuli — for example, a touch-me-not plant folds its leaves when touched
- They respire, meaning they release energy from food
- They eventually undergo excretion, removing waste from their body
Not every organism shows all these signs obviously — a seed lying in a packet doesn't look alive at all, yet it is, because it has the potential to grow when conditions are right.
Grouping Living Things: Why Do We Classify?
Imagine a library where books are just thrown onto shelves with no order — fiction mixed with science textbooks mixed with cookbooks. Finding anything would be a nightmare. Scientists faced a similar problem with the millions of living species on Earth, so they came up with systems of classification — sorting organisms into groups based on shared characteristics.
Classification makes it easier to:
- Study organisms in an organised way
- Understand relationships between different species
- Identify unknown organisms by comparing features
- Communicate clearly about organisms using consistent names
The Basis of Classification
Organisms are usually grouped according to features such as:
| Feature Considered | Example |
|---|---|
| Body structure | Presence or absence of a backbone |
| Habitat | Land-dwelling, water-dwelling, or both |
| Method of nutrition | Self-making food (plants) vs depending on others (animals) |
| Reproduction | Seeds, eggs, live birth, spores |
| Cell structure | Single-celled or many-celled organisms |
Plants and Animals — The Two Familiar Groups
Most students naturally divide the living world into "plants" and "animals," and that's a reasonable starting point, even though scientists now recognise several more groups (like fungi and microorganisms) beyond just these two.
Plants generally stay fixed in one place, make their own food using sunlight (a process you'll study in detail later, called photosynthesis), and have a green colour due to a pigment called chlorophyll.
Animals, on the other hand, usually move from place to place in search of food, cannot make their own food, and depend on plants or other animals for nutrition.
Within plants and animals, there's still enormous variety. Some plants are as small as duckweed floating on a pond; others, like the banyan tree, can spread across acres. Some animals like earthworms have no visible eyes or legs, while others like eagles have sharp vision and powerful wings.
Diversity Among Plants
Plants are often grouped based on their size, the strength of their stem, and whether they carry seeds or not.
- Herbs – small plants with soft, green, and delicate stems (example: tulsi, spinach)
- Shrubs – medium-sized plants with woody stems that branch out close to the ground (example: rose, henna)
- Trees – tall plants with a hard, woody stem called a trunk (example: neem, mango)
- Climbers – weak-stemmed plants that use support to climb upward (example: money plant, grapevine)
- Creepers – plants with weak stems that spread along the ground (example: pumpkin, watermelon)
Diversity Among Animals
Animals show even more dramatic diversity, since they live in almost every possible environment on Earth — underground, underwater, in the air, and on land.
A rough (and useful) way to begin grouping animals is by whether or not they have a backbone:
- Vertebrates — animals with a backbone (fish, frogs, lizards, birds, humans)
- Invertebrates — animals without a backbone (earthworms, snails, insects, jellyfish)
Interestingly, invertebrates actually make up the majority of animal species on Earth, even though we tend to notice vertebrates more in daily life.
Habitat and Its Role in Diversity
A habitat is simply the natural place where an organism lives and finds everything it needs — food, shelter, and conditions suited to its survival. Different habitats support very different life forms:
- Terrestrial habitats – land-based, such as forests, deserts, and grasslands
- Aquatic habitats – water-based, such as rivers, ponds, and oceans
Organisms living in extreme habitats often show special features. A cactus, for instance, has thick, waxy stems and reduced leaves (spines) to survive with minimal water in a desert. A fish has fins and gills — features that would be completely useless on land but are essential underwater.
This connection between habitat and body features is a good example of how diversity isn't accidental — it's shaped by the need to survive in a particular environment.
Key Terms to Remember
- Diversity – the presence of a wide variety of living organisms, differing in structure, habitat, and behaviour
- Classification – grouping organisms based on shared characteristics
- Habitat – the natural home or surroundings where an organism lives
- Vertebrates – animals possessing a backbone
- Invertebrates – animals lacking a backbone
- Herbs, shrubs, trees, climbers, creepers – categories of plants based on stem type and size
Quick Revision – Key Points (Chapter Summary)
- The living world shows enormous diversity, shaped largely by differences in habitat and survival needs.
- Living organisms share certain common characteristics — movement, growth, nutrition, reproduction, respiration, and response to stimuli.
- Classification helps scientists study and organise the huge number of species on Earth in a systematic way.
- Plants are broadly grouped as herbs, shrubs, trees, climbers, and creepers.
- Animals are broadly grouped as vertebrates (with a backbone) and invertebrates (without a backbone).
- A habitat provides everything an organism needs to survive, and organisms often develop special features suited to their particular habitat.
Possible Exam Questions from This Chapter
- What is meant by diversity in the living world? Give two examples.
- List any five characteristics common to all living organisms.
- Why do scientists classify living organisms?
- Differentiate between vertebrates and invertebrates with examples.
- Explain the difference between a herb, a shrub, and a tree.
- How does habitat influence the features of an organism? Give one example.
These notes are based on the new NCERT Class 6 Science textbook, Chapter: Diversity in the Living World, and are designed for quick and complete revision.
Comments
Post a Comment