Class 9 Science Exploration Chapter 12 Solutions (NCERT 2026–27) – Patterns in Life: Diversity and Classification

These Class 9 Science Exploration Chapter 12 solutions cover Patterns in Life: Diversity and Classification from the new NCF-2023 textbook (2026–27).

Class: 9 Subject: Science Book: Exploration Chapter: 12 Exercise: Revise, Reflect, Refine (15 Qs) Session: 2026–27
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Class 9 Science Exploration Chapter 12 Solutions – Overview

Chapter 12 of Exploration, Patterns in Life: Diversity and Classification, explains the huge biodiversity of life and why we need to classify organisms. It covers the basis of classification (cellular organisation, number of cells and mode of nutrition), Whittaker’s five kingdom classification (Monera, Protista, Fungi, Plantae and Animalia), the main groups of plants and animals, the classification hierarchy, and why viruses are kept outside the system. These Class 9 Science Exploration Chapter 12 solutions answer every textbook question step by step.

Key Concepts & Definitions

Biodiversity: the variety of living organisms — their species, forms and habitats.

Classification: arranging organisms into groups based on shared characteristics.

Basis of classification: cellular organisation (prokaryotic / eukaryotic), number of cells (unicellular / multicellular) and mode of nutrition (autotrophic / heterotrophic).

Five kingdoms (Whittaker): Monera (prokaryotes), Protista (unicellular eukaryotes), Fungi (heterotrophic, chitin cell wall), Plantae (autotrophic, cellulose cell wall) and Animalia (heterotrophic, no cell wall).

Classification hierarchy: Kingdom → Phylum → Class → Order → Family → Genus → Species (going down, fewer members but more shared features).

Viruses: acellular; active only inside a host — kept outside the five kingdoms.

“Think It Over” — Answers

What do you understand by biodiversity, and why is there such an enormous variety of life on Earth?

ANSWERBiodiversity is the huge variety of living organisms — the different species, their forms and the habitats they live in. This variety has arisen because organisms have adapted over a very long time to many different environments and ways of life, and each one plays a role in keeping nature in balance.

On what basis are organisms classified into groups?

ANSWEROrganisms are grouped by their shared characteristics — cellular organisation (prokaryotic or eukaryotic), number of cells (unicellular or multicellular), mode of nutrition (autotrophic or heterotrophic) and body design — so that similar organisms are placed together. This makes the vast diversity of life easier to study and reflects evolutionary relationships.

Class 9 Science Exploration Chapter 12 Solutions — Revise, Reflect, Refine

1. Meena and Hari observed an animal in their garden. Hari called it an insect while Meena said it was an earthworm. Choose the correct option that confirms it is an insect. (i) Bilateral symmetrical body (ii) Body with jointed legs (iii) Cylindrical body (iv) Body with little segmentation

ANSWERCorrect option: (ii) Body with jointed legs. Insects are arthropods and have jointed legs, while an earthworm has a soft, segmented body without jointed legs.

2. Sponges lack true tissues and organs. Which feature of sponge cells supports their classification under the animal kingdom? (i) Absence of mitochondria (ii) Ability to photosynthesise (iii) Presence of a cell membrane (iv) Presence of a cell wall

ANSWERCorrect option: (iii) Presence of a cell membrane. Animal cells have only a cell membrane and no cell wall, and they cannot photosynthesise — this is why sponges (heterotrophic, no cell wall) are placed in Animalia.

3. Observe two different animals in your environment. What features help you distinguish between them, and how do these features help place them into different groups?

ANSWER Useful distinguishing features include body symmetry, presence or absence of a backbone, number and type of legs, body covering (scales, feathers or fur), and the way the animal moves and reproduces. For example, a sparrow has feathers, wings and a beak and lays eggs (it is a bird), while a cat has fur and four legs and gives birth to young (it is a mammal). Such shared features let us place each animal into its correct group.

4. How would a scientist justify choosing cellular organisation as a more fundamental characteristic for classification than the presence of xylem and phloem?

ANSWER Cellular organisation (prokaryotic vs eukaryotic, unicellular vs multicellular) is a universal feature present in every living organism, so it can be used to classify all forms of life. Xylem and phloem are found only in some plants (vascular plants), so they cannot classify animals, fungi or bacteria. A fundamental characteristic must apply broadly and reflect basic body design — which cellular organisation does.

5. You find an unlabelled slide of a single-celled organism with a well-defined nucleus and multiple cilia. Which group would it most likely belong to? Give reasons.

ANSWER It would most likely belong to the Kingdom Protista (for example, Paramecium). Reasons: it is unicellular and has a well-defined (true) nucleus, so it is a single-celled eukaryote, and the cilia are used for movement — all typical of protists.

6. How does the diversity of organisms contribute to the balance and stability of an ecosystem?

ANSWER A variety of organisms fill different roles — producers, consumers and decomposers — and link together in food chains and webs, which keeps energy and nutrients cycling. Greater diversity makes the ecosystem more stable and resilient: if one species declines, others can take over its role, so the ecosystem can recover from disturbances and diseases.

7. If all unicellular organisms were grouped into a single kingdom, what problems would arise?

ANSWER Unicellular organisms are very different from one another: some are prokaryotic (bacteria, no true nucleus) and some are eukaryotic (protists, with a true nucleus); some are autotrophic and some heterotrophic; some have cell walls and some do not. Putting them all together would ignore these fundamental differences — especially the basic prokaryote–eukaryote divide — making the classification inaccurate and unhelpful.

8. Viruses were studied in earlier classes. Why are they not placed in any of the five kingdoms? Give reasons.

ANSWER Viruses are acellular — they are not made of cells, so they have no cellular organisation, which the five kingdom system is based on. They cannot carry out life processes such as growth, metabolism or reproduction on their own; they become active and multiply only inside a host cell, and are inert outside it. Showing features of both living and non-living things, they are kept outside the five kingdoms.

9. If you were asked to revise the five kingdom classification, would you create a separate category for viruses or keep them outside the system? Justify your answer and explain what this indicates about the evolving nature of classification.

ANSWER A reasonable choice is to create a separate category for viruses, because they are unique — acellular and on the borderline between living and non-living — so a separate group recognises their distinct nature without forcing them into a kingdom of cellular organisms. This shows that scientific classification is dynamic and evolving: it is revised as new knowledge is gained and as organisms (or entities like viruses) are found that do not fit the existing scheme.

10. Viruses contain genetic material like living organisms but lack cellular organisation. Which features prevent them from fitting into the five kingdom system, and what does this tell us about the limitations of classification systems?

ANSWER Features that prevent them fitting in: they are acellular (no cell, no cytoplasm or organelles) and cannot perform metabolism or reproduce on their own — they need a host cell. The five kingdom system requires cellular organisation. This shows that classification systems are human-made frameworks based on chosen criteria; they cannot always accommodate every entity (especially borderline cases) and must be revised as our understanding grows.

11. Both pteridophytes and bryophytes lack flowers and seeds, yet they are placed in different groups. Explain this classification using their key features.

ANSWER Bryophytes (e.g., mosses) lack true vascular tissue (no xylem and phloem) and do not have true roots, stems and leaves — they have a simple body with root-like rhizoids and grow in moist places. Pteridophytes (e.g., ferns) have true vascular tissue (xylem and phloem) and well-differentiated true roots, stems and leaves. So, although both lack flowers and seeds, the presence or absence of vascular tissue and a differentiated plant body places them in different groups.

12. In the classification hierarchy, which group — class or genus — has fewer members but more features in common? Explain.

ANSWER Genus has fewer members but more features in common. As we move down the hierarchy (Kingdom → … → Class → … → Genus → Species), the number of organisms in a group decreases while the characteristics they share increase. Genus is below class, so its members are fewer and more alike.

13. A scientist discovers a new organism that shows both locomotion and autotrophic nutrition. Which character(s) would help identify it as belonging to Protista?

ANSWER If the organism is unicellular with a true nucleus (a single-celled eukaryote) and shows both locomotion (using flagella, cilia or pseudopodia) and autotrophic (photosynthetic) nutrition, these mixed plant-like and animal-like features place it in Protista (like Euglena).

14. A researcher identified a unicellular eukaryotic organism as fungi. What identification key would you suggest to keep a unicellular organism in the Kingdom Fungi?

ANSWER Key features of Fungi: a cell wall made of chitin, a heterotrophic (saprophytic) mode of nutrition (absorbing food from dead organic matter), and no chlorophyll (non-photosynthetic). So even a unicellular organism (such as yeast) is placed in Fungi if it has a chitinous cell wall and feeds by absorption — these characters distinguish it from a protist.

15. Students recorded only the features of organisms P–T (not their names):

CASE DATA
OrganismKey observations
PMicroscopic; no true nucleus; rigid cell covering; survives high salinity and temperature.
QMulticellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter.
RUnicellular; true nucleus; contractile vacuole; moves using flagella; photosynthesis in light but heterotrophic in the dark.
SMulticellular; well-differentiated tissues; backbone present; aquatic respiration in early life stage.
TAcellular; contains genetic material; remains inactive outside a host cell.

Answer the following based on the case study: (i) Identify one organism that clearly belongs to Kingdom Fungi and give one supporting observation. (ii) Which organism would be placed in Kingdom Monera, and what characteristic justifies it? (iii) R and Q are both eukaryotic, yet are placed in different kingdoms. Analyse the criteria that separate them. (iv) Why can organism S not be classified using mode of nutrition alone? (v) Organism T does not fit any of the five kingdoms. Which fundamental characteristic does it lack, and what does this reveal? (vi) If classification were based only on habitat, which organisms might be incorrectly grouped, and what are the consequences? (vii) A new organism is multicellular, eukaryotic, lacks chlorophyll and absorbs nutrients from a host externally. Should it be placed under Fungi or Animalia? Justify.

ANSWER (i) Q belongs to Fungi — it is a multicellular, filamentous organism with a cell wall but no chlorophyll, growing on dead organic matter (saprophytic). (ii) P belongs to Monera — it has no true nucleus (it is a prokaryote). (iii) R is unicellular and can be autotrophic (photosynthetic), so it is a protist; Q is multicellular and heterotrophic (saprophytic), so it is a fungus. They differ in number of cells and mode of nutrition. (iv) S is heterotrophic, but so are fungi and many other organisms, so nutrition alone cannot place it. Other features — multicellular body, well-differentiated tissues and a backbone — are needed to classify it as an animal (Animalia). (v) T (a virus) lacks cellular organisation — the fundamental basis of the five kingdom system. This reveals that classification systems based on cells cannot accommodate acellular entities and may need revision. (vi) If habitat alone were used, very different organisms sharing a habitat (for example a bacterium, a protist and a fish all from a pond) would be wrongly grouped together, while related organisms in different habitats would be separated — the classification would ignore real relationships and become inaccurate. (vii) It should be placed under Fungi: like fungi it is multicellular, eukaryotic, lacks chlorophyll and feeds by external absorption. Animals are also heterotrophic but they ingest food rather than absorb it, so absorption-based nutrition points to Fungi.

Common Mistakes to Avoid

Watch out for these

  • Mixing up the kingdoms — Monera (prokaryote), Protista (unicellular eukaryote), Fungi (chitin wall, absorptive), Plantae (autotroph), Animalia (heterotroph, no wall).
  • Thinking all unicellular organisms are the same — the prokaryote vs eukaryote difference is fundamental.
  • Classifying animals by nutrition alone — many groups are heterotrophic, so other features are needed.
  • Confusing fungi (absorb nutrients) with animals (ingest food).
  • Forgetting that going down the hierarchy means fewer members but more shared features.
  • Trying to fit viruses into a kingdom — they are acellular and kept outside.

Extra Practice Questions

Very Short Answer Type Questions

Q1. Who proposed the five kingdom classification?

ANSWERR. H. Whittaker.

Q2. To which kingdom do bacteria belong?

ANSWERKingdom Monera.

Q3. What is the cell wall of fungi made of?

ANSWERChitin.

Short Answer Type Questions

Q1. Differentiate between Kingdom Monera and Kingdom Protista.

ANSWERMonera contains prokaryotes (no true nucleus or membrane-bound organelles), e.g., bacteria; Protista contains unicellular eukaryotes (a true nucleus and organelles), e.g., Amoeba and Paramecium.

Q2. Why is classification necessary?

ANSWERBecause there is an enormous variety of organisms; classification arranges them into groups by shared features, which makes them easier to study, identify and understand, and shows their relationships.

Long Answer Type Question

Q1. Describe the five kingdoms of Whittaker’s classification with one example each.

ANSWER Monera: prokaryotic, unicellular, with or without cell wall — e.g., bacteria. Protista: unicellular eukaryotes — e.g., Amoeba, Paramecium, Euglena. Fungi: eukaryotic, heterotrophic (saprophytic), chitin cell wall — e.g., yeast, mushrooms. Plantae: multicellular, autotrophic (photosynthetic), cellulose cell wall — e.g., mosses, ferns, flowering plants. Animalia: multicellular, heterotrophic, no cell wall — e.g., insects, fish, mammals.

MCQs & Assertion–Reason

1. The five kingdom classification was given by:

(a) Linnaeus    (b) Whittaker    (c) Haeckel    (d) Darwin

2. Organisms without a true nucleus belong to:

(a) Protista    (b) Fungi    (c) Monera    (d) Plantae

3. The cell wall of fungi is made of:

(a) cellulose    (b) chitin    (c) protein    (d) lipid

4. Which kingdom contains only unicellular eukaryotes?

(a) Monera    (b) Protista    (c) Fungi    (d) Animalia

5. Insects belong to the phylum:

(a) Annelida    (b) Arthropoda    (c) Mollusca    (d) Porifera

6. Which of these is the smallest unit of classification?

(a) kingdom    (b) class    (c) genus    (d) species

7. Plants with vascular tissue but no seeds are:

(a) bryophytes    (b) pteridophytes    (c) gymnosperms    (d) angiosperms

8. Members of Animalia are:

(a) autotrophic    (b) heterotrophic    (c) prokaryotic    (d) photosynthetic

9. Viruses are placed:

(a) in Monera    (b) in Protista    (c) outside the five kingdoms    (d) in Fungi

10. Euglena shows characteristics of both plants and animals, so it is placed in:

(a) Plantae    (b) Animalia    (c) Protista    (d) Monera

Answer key: 1-(b), 2-(c), 3-(b), 4-(b), 5-(b), 6-(d), 7-(b), 8-(b), 9-(c), 10-(c).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: Bacteria are placed in Kingdom Monera.

Reason: They are prokaryotes with no true nucleus.

A-R 2. Assertion: Viruses are not included in the five kingdoms.

Reason: They lack cellular organisation.

A-R 3. Assertion: Going down the classification hierarchy, the number of shared features increases.

Reason: Lower groups contain fewer, more closely related organisms.

A-R 4. Assertion: All members of Plantae are heterotrophic.

Reason: Plants have chlorophyll and a cellulose cell wall.

A-R 5. Assertion: Pteridophytes are placed in a different group from bryophytes.

Reason: Pteridophytes have true vascular tissue while bryophytes do not.

Answer key: 1-(A), 2-(A), 3-(A), 4-(D), 5-(A).

Quick Revision Summary

  • Biodiversity is the variety of life; classification groups organisms by shared features.
  • Basis of classification: cellular organisation, number of cells, mode of nutrition.
  • Five kingdoms: Monera, Protista, Fungi, Plantae, Animalia.
  • Hierarchy: Kingdom → Phylum → Class → Order → Family → Genus → Species (fewer members, more shared features going down).
  • Bryophytes lack vascular tissue; pteridophytes have it.
  • Viruses are acellular and kept outside the five kingdoms — classification is an evolving system.

Real-life Applications

Classification underpins much of biology and daily life: it helps scientists identify and name new species, understand evolutionary relationships, find useful organisms (medicinal plants, antibiotic-producing fungi), manage crops and pests, conserve biodiversity, and track disease-causing microbes — all by organising the enormous variety of life into meaningful groups.

How to score full marks in this chapter

Learn the defining feature of each kingdom (nucleus, cell wall type, number of cells, nutrition) and use more than one feature when classifying. Remember the hierarchy order, the bryophyte vs pteridophyte difference, and always explain why viruses sit outside the five kingdoms.

Frequently Asked Questions

What is Class 9 Science Exploration Chapter 12 about?

Diversity and classification — biodiversity, the basis of classification, Whittaker’s five kingdoms, plant and animal groups, the classification hierarchy, and why viruses are kept outside the system.

What are the five kingdoms?

Monera, Protista, Fungi, Plantae and Animalia, based on cellular organisation, number of cells and mode of nutrition.

Why are viruses not placed in any kingdom?

Because they are acellular and become active only inside a host, so they do not fit the five kingdom system built on cellular organisms.

Are these Class 9 Science Exploration Chapter 12 solutions free?

Yes. All solutions are free and follow the official NCERT Exploration textbook for 2026–27.

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