---
title: "NCERT Solutions Class 9 Science Patterns in Life: Diversity and Classification"
url: https://www.swavid.com/science/class/9/chapter/patterns-in-life-diversity-and-classification/ncert-solutions
dateModified: 2026-10-07T16:39:20+00:00
---

# NCERT Solutions Class 9 Science Patterns in Life: Diversity and Classification

This chapter's questions cover the understanding of biodiversity, classification systems, and the criteria used to group living organisms from prokaryotes to complex plants and animals.

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## Think It Over (Page 228)

### Question 1

*3 marks · Short answer*

What do you understand by biodiversity?

**Solution**

1. The immense variety of living organisms existing in countless forms and habitats on Earth is known as biodiversity.
2. It includes everything from microscopic organisms to giant trees and animals.
3. Every organism plays a vital role in keeping nature stable and functioning, such as providing oxygen, decomposing waste, and pollinating flowers.

**Answer:** Biodiversity refers to the immense variety of living organisms on Earth, which is essential for maintaining a stable and functioning ecosystem.

> Common mistake: Confining biodiversity only to animals or plants, forgetting microorganisms.

### Question 2

*3 marks · Short answer*

How does the grouping of organisms help us understand diversity?

**Solution**

1. Grouping and classifying organisms based on shared characteristics and evolutionary relationships make the study of vast biological diversity organized and systematic.
2. It helps us understand the similarities and differences among living beings.
3. It also allows us to understand how different organisms are related to one another and how they interact in ecosystems.

**Answer:** Grouping organisms organizes information, reveals relationships and similarities among them, and makes the study of biological diversity systematic.

> Common mistake: Stating that grouping is only done for naming rather than understanding relationships and systematic study.

### Question 3

*3 marks · Short answer*

On what basis, are plants and animals classified?

**Solution**

1. Plants and animals are classified using a number of characteristics such as external features, mode of nutrition, and internal structures.
2. Other important criteria include cell structure (prokaryotic or eukaryotic, unicellular or multicellular, presence of cell wall), ecological role, and reproduction methods.
3. Scientists also use genetic similarity studied through DNA to determine evolutionary relationships and common ancestry.

**Answer:** Plants and animals are classified on the basis of shared characteristics such as cell structure, mode of nutrition, internal organisation, and genetic similarity.

> Common mistake: Listing only external appearance while ignoring internal cellular and genetic features.

### Question 4

*3 marks · Short answer*

How does classification help address problems in farming?

**Solution**

1. Classification helps identify diverse crop varieties with useful characteristics such as drought tolerance, pest resistance, and the ability to grow in nutrient-poor soils.
2. Understanding plant relationships helps farmers realize that diversity reduces the risk of crop failure.
3. It aids in sustainable farming practices, ecosystem management, and strengthening food security.

**Answer:** Classification helps address problems in farming by identifying beneficial traits like pest resistance and drought tolerance, which reduce crop failure and strengthen food security.

> Common mistake: Focusing only on general biological classification without connecting it to agricultural applications like crop resistance and food security.

## Activity 12.1: Let us compare and classify (Page 230)

### Question 1

*3 marks · Case-based*

Ponder on the questions given below: 
- Which animals can you identify in the given picture?
- Where are they seen?
- Which animals in the picture seem active: 
(i) during the day?
(ii) during the night?
(iii) both during the day and the night?

**Part (i)**

1. Observe Fig. 12.2 for animals active during the day.
2. Birds like eagles, peafowls, and mammals like tigers and leopards are seen active during the day.

Answer (i): Birds (eagles, peafowls) and mammals (tigers, leopards) are active during the day.

**Part (ii)**

1. Observe Fig. 12.2 for animals active during the night.
2. Nocturnal animals such as owls are active during the night.

Answer (ii): Owls are active during the night.

**Part (iii)**

1. Observe Fig. 12.2 for animals that are active during both day and night.
2. Certain animals and insects may remain active across day and night cycles depending on the ecosystem.

Answer (iii): Certain insects and small mammals are active both during the day and the night.

**Answer:** Animals in the ecosystem are active at different times of the day, with some active during daytime, some at night, and some both.

> Common mistake: Confusing nocturnal and diurnal animals.

### Question 2

*Activity*

Record your observations in Table 12.1.

**Solution**

1. Observe different organisms in the ecosystem illustration (Fig. 12.2).
2. Record their location, active time, and visible features in Table 12.1.

**Answer:** Organisms are recorded based on habitat, activity time, and visible features.

> Common mistake: Failing to note specific observable features like feathers or fur.

### Question 3

*Activity*

Now, try grouping the same organisms in more than one way. Each time change the criterion you are using for grouping (Table 12.2).

**Solution**

1. Select a grouping criterion such as habitat, mode of nutrition, or body covering.
2. Group organisms that share the chosen criterion and note the pattern.

**Answer:** Organisms can be grouped in multiple ways by changing the classification criterion.

> Common mistake: Using multiple criteria simultaneously instead of one criterion at a time.

## Pause and Ponder (Page 231)

### Question 1

*3 marks · Short answer*

If many organisms share common features, could they also share a common ancestry?

**Solution**

1. Yes, organisms that share many common features are considered to have evolved from common ancestors.
2. Similar external and internal features, cell structures, or genetic material (DNA) suggest that these organisms inherited these traits from a shared ancestral form over evolutionary time.
3. Biological classification groups such organisms together based on these shared similarities to understand their evolutionary relationships.

**Answer:** Yes, organisms sharing common features often share a common ancestry due to inherited traits passed down through generations.

> Common mistake: Stating that organisms share ancestry just by living in the same habitat instead of considering their inherited biological features.

## Activity 12.2: Let us read a case study (Page 232)

### Question 1

*4 marks · Case-based*

Think and discuss the case based on the following questions —
(i) How can scientists keep track of so many species?
(ii) The four hornbills look similar in some ways. What features can help scientists distinguish them from one another?
(iii) What would happen if the large, old trees disappeared from the forest?

**Part (i)**

1. Scientists keep track of a vast number of species by using biological classification.
2. They group organisms systematically based on their shared characteristics and differences.

Answer (i): Scientists keep track of many species through biological classification, which systematically groups organisms based on shared characteristics.

**Part (ii)**

1. The four hornbill species can be distinguished by observing their external features.
2. Specific differences in bill shape, size, coloration, and patterns on their casque help scientists tell them apart.

Answer (ii): Distinct external features such as bill shape, size, and coloration help scientists distinguish between the four hornbill species.

**Part (iii)**

1. Large, old trees provide suitable cavities for hornbills to nest in.
2. If these trees disappeared, hornbills would lose their natural nesting sites, leading to a decline in their population.

Answer (iii): If large, old trees disappeared, hornbills would lose their nesting sites, adversely affecting their survival and reproduction.

**Answer:** Scientists keep track of species through biological classification, distinguish hornbills using specific external features like bill structure and coloration, and rely on old trees since hornbills depend on them for nesting.

> Common mistake: Failing to connect the specific ecological needs of organisms like nesting habits to habitat features.

## Activity 12.3: Let us study (Page 234)

### Question 1

*Activity*

Study the concept map (Fig. 12.5).

**Solution**

1. The concept map (Fig. 12.5) illustrates the hierarchical criteria used to classify living organisms into the five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.
2. Observation shows how organisms branch based on cell type, level of organisation, cell structure, and mode of nutrition.

**Answer:** The concept map visually represents the criteria used in the five kingdom classification system.

### Question 2

*3 marks · Short answer*

List the criteria which form the basis of five kingdom classification.

**Solution**

1. Based on the concept map in Fig. 12.5, the five kingdom classification is based on specific key criteria.
2. The criteria include cell type (prokaryotic or eukaryotic), level of organisation (unicellular or multicellular), cell structure (presence or absence of a cell wall, and composition of the cell wall such as chitin or cellulose), and mode of nutrition (autotrophic or heterotrophic).
3. Ecological roles such as producers, consumers, or decomposers also form part of the criteria.

**Answer:** The basis of the five kingdom classification includes cell type, level of organisation, cell structure, and mode of nutrition.

> Common mistake: Listing only nutrition or cell type instead of all the combined criteria shown in the concept map.

### Question 3

*3 marks · Short answer*

Compare the criteria you have listed after studying the concept map and the criteria given below:
- Cell type — prokaryote or eukaryote
- Cell structure — presence or absence of a cell wall
- Level of organisation — unicellular or multicellular
- Mode of nutrition — autotrophic or heterotrophic

**Solution**

1. The criteria listed from the concept map directly match the given criteria used by Whittaker.
2. Cell type distinguishes primitive prokaryotes (Monera) from eukaryotes with membrane-bound nuclei.
3. Cell structure (such as chitin or cellulose cell walls or no cell wall), level of organisation (unicellular or multicellular), and mode of nutrition (autotrophic or heterotrophic) separate Fungi, Plantae, Animalia, and Protista.

**Answer:** The listed criteria match Whittaker's criteria of cell type, cell structure, level of organisation, and mode of nutrition.

> Common mistake: Confusing the order or categories of cell walls between fungi and plants.

## Activity 12.4: Let us explore (Page 235)

### Question 1

*Activity*

In the school laboratory, observe the available permanent slides of bacteria and cyanobacteria under the microscope.

**Solution**

1. Focus the permanent slides of bacteria and cyanobacteria under the high power of a compound microscope.
2. Observe the single-celled prokaryotic structure and note that they lack a well-defined membrane-bound nucleus.

**Answer:** Bacteria and cyanobacteria appear as single-celled microscopic structures lacking a true nucleus.

### Question 2

*Activity*

Compare them with Fig. 12.6.

**Solution**

1. Compare the shapes and forms seen under the microscope with the illustrations of Monera in Fig. 12.6.
2. Note the presence of bacillus (rod-like), coccus (spherical), spirillum (spiral), and filamentous cyanobacterial forms.

**Answer:** The observed slides match the diverse shapes of Monera shown in Fig. 12.6.

## Pause and Ponder (Page 236)

### Question 2

*3 marks · Short answer*

How can a single-celled organism carry out all its life processes when billions of cells are required to perform similar functions in multicellular organisms like us?

**Solution**

1. A single-celled organism carries out all essential life processes within its single cell using specialised structures or organelles.
2. It interacts directly with its surrounding environment for the exchange of gases, intake of nutrients, and removal of waste.
3. In contrast, multicellular organisms have billions of cells organised into specialised tissues, organs, and organ systems to divide complex functions.

**Answer:** Single-celled organisms perform all life processes within one cell using organelles and direct environmental contact, whereas multicellular organisms distribute these functions among specialised cells, tissues, and organ systems.

> Common mistake: Stating that single-celled organisms have organs or tissues, which are only present in multicellular organisms.

## Activity 12.6: Let us explore (Page 238)

### Question 1

*Activity*

Observe some bryophytes with the help of a hand lens. Collect them in a watch glass.

**Solution**

1. Collect some bryophytes such as mosses using a hand lens to observe their external features closely.
2. Observation: The plant body shows slight differentiation into stem-like and leaf-like structures with root-like rhizoids, lacking true roots, stems, and leaves.

**Answer:** Bryophytes show a simple, non-differentiated body compared to higher plants, possessing rhizoids instead of true roots.

### Question 2

*Activity*

Put a drop of water on it and observe it under a dissecting microscope. How do they differ from the leaves that you usually observe in plants in your surroundings?

**Solution**

1. Place a drop of water on the collected bryophyte specimen and observe it under a dissecting microscope.
2. Observation: The structures appear thin, often only a few cells thick, lacking specialised vascular tissues (xylem and phloem) which are typically present in the leaves of surrounding higher plants.

**Answer:** Unlike the leaves of higher plants, bryophyte leaves lack a complex vascular system and true internal tissue differentiation.

## Pause and Ponder (Page 238)

### Question 3

*3 marks · Short answer*

Which plant features reduce their dependence on water but still require moist conditions?

**Solution**

1. Bryophytes and pteridophytes possess features like specialized body structures, rhizoids, or true roots and stems that allow them to live on land.
2. However, they still require external water for the swimming of male gametes during reproduction.
3. Therefore, damp soil and moist conditions are essential for their fertilization and survival.

**Answer:** Features like a land-adapted body help them survive on land, but they still need moisture for swimming male gametes during reproduction.

> Common mistake: Confusing land adaptation with complete independence from water for reproduction.

### Question 4

*3 marks · Short answer*

Why do taller plants need specialised transport tissues?

**Solution**

1. Taller plants have a large height and span a significant distance between the roots (which absorb water) and the leaves (which prepare food).
2. Simple diffusion is too slow and inefficient to transport water, minerals, and food over such long distances.
3. Therefore, taller plants need specialised vascular tissues, namely xylem and phloem, to efficiently transport water and nutrients to all parts of the plant.

**Answer:** Taller plants need specialised transport tissues (xylem and phloem) to efficiently carry water, minerals, and food over long distances from where they are absorbed or produced to distant parts of the plant body.

> Common mistake: Stating only that they need transport without explaining the limitation of simple transport over long distances.

### Question 5

*3 marks · Short answer*

How do seeds and fruits affect, where and how plants can survive?

**Solution**

1. Seeds protect the developing plant embryo and contain stored food to support its initial growth, allowing survival during unfavorable conditions without needing external water for fertilisation.
2. Fruits enclose the seeds and help in their dispersal to new locations through agents like wind, water, animals, and birds.
3. These features enable plants to colonise a wide range of environments, reducing overcrowding and expanding their geographical distribution.

**Answer:** Seeds protect the embryo and provide stored food for survival during harsh conditions, while fruits assist in seed dispersal to new locations, enabling plants to successfully survive and spread across diverse environments.

> Common mistake: Confusing the function of seeds with that of flowers or confusing seed protection with fruit dispersal mechanisms.

## Activity 12.7: Let us compare (Page 238)

### Question 1

*Activity*

Recall the cross section of the sunflower stem you have studied in Chapter 3 (Fig. 3.7).

**Solution**

1. Recall that the sunflower stem is an angiosperm showing well-developed internal structures, including vascular bundles arranged in a ring containing both xylem and phloem for transport.

**Answer:** The cross section of a sunflower stem shows distinct vascular bundles arranged in a ring with functional xylem and phloem.

### Question 2

*Activity*

Compare the cross section of the stem of a fern, a pteridophytic plant (Fig. 12.11) with a cross section of sunflower stem you studied in Chapter 3 (Fig. 3.7).

**Solution**

1. Observe the cross section of the fern stem in Fig. 12.11, which shows specialised vascular tissues, namely xylem and phloem.
2. Compare this with the sunflower stem cross section from Chapter 3 to note the presence of vascular tissues in both pteridophytes and higher plants like angiosperms.

**Answer:** Both the fern stem and the sunflower stem possess specialised vascular tissues (xylem and phloem) for transporting water and food throughout the plant.

### Question 3

*Activity*

What difference do you observe in the vascular tissue of the fern stem and of the stem of higher plants? Write your observations. Share and discuss them in class.

**Solution**

1. Examine the arrangement and complexity of vascular bundles in the fern stem compared to higher angiospermic plants like the sunflower.
2. Note that while pteridophytes like ferns possess vascular tissues (xylem and phloem), higher plants exhibit a more advanced and organised tissue system supporting complex body structures and secondary growth.

**Answer:** Higher plants possess a more complex, well-developed, and structurally organised vascular tissue system compared to the simpler vascular arrangement found in ferns.

## Activity 12.8: Let us discuss (Page 239)

### Question 1

*Activity*

Collect different leaves from your surroundings, and observe their shape and venation. Group them as monocots or dicots. Discuss how their structures help them adapt in different conditions to survive.

**Solution**

1. Collect different leaves from the surroundings and observe their shape and venation patterns.
2. Group leaves with parallel venation as monocots and those with reticulate (net-like) venation as dicots.
3. Discuss how parallel venation and narrow shapes help monocots withstand strong winds, while broad blades with reticulate venation help dicots capture maximum sunlight for photosynthesis.

**Answer:** Leaves are grouped into monocots (parallel venation) and dicots (reticulate venation), with structural adaptations helping them survive in varying environmental conditions.

> Common mistake: Confusing parallel venation with reticulate venation.

## Activity 12.9: Let us study (Page 239)

### Question 1

*Activity*

Carefully study the salient features of each plant group.

**Solution**

1. Study the salient features of plant groups including Thallophyta, Bryophyta, Pteridophyta, Gymnosperm, and Angiosperm from Table 12.3 in the textbook.
2. Observe how each plant group possesses specific adaptations in body structure, reproduction, and transport systems to survive in different environments.

**Answer:** Salient features of all five plant groups of Kingdom Plantae have been studied from Table 12.3.

### Question 2

*Activity*

Analyse the salient features, and write the advantages for survival of the group and the exceptions or challenges faced in the given columns.

**Solution**

1. Analyse the advantages for survival for each group, such as simple bodies for water dispersal in thallophytes, vascular systems in pteridophytes, and flowers and fruits in angiosperms.
2. Note the challenges and exceptions, such as dependence on water for reproduction in bryophytes and pteridophytes, and lack of fruit-enclosed seeds in gymnosperms.

**Answer:** The advantages, challenges, and exceptions for survival for each plant group have been analysed and recorded as per Table 12.3.

## Pause and Ponder (Page 242)

### Question 6

*3 marks · Short answer*

An earthworm (annelida) and a beetle (arthropoda), both have segmented bodies but the beetle has a hard external skeleton. How does the beetle’s external skeleton help it survive?

**Solution**

1. The hard external skeleton (exoskeleton) of the beetle provides physical protection from predators and environmental hazards.
2. It significantly reduces water loss from the body, allowing the beetle to survive and thrive in dry and exposed terrestrial environments.
3. It also supports powerful muscles required for locomotion and active movement.

**Answer:** The beetle's external skeleton provides protection, reduces water loss, and supports powerful muscles for survival in dry and exposed environments.

> Common mistake: Confusing the function of an exoskeleton with internal bones or thinking it is used for digestion.

## Pause and Ponder (Page 247)

### Question 7

*3 marks · Short answer*

Does the term ‘biodiversity’ relate only to the variety of organisms, or does it encompass other elements?

**Solution**

1. The term biodiversity refers to the immense variety of all living organisms on the Earth.
2. It encompasses not only the variety of organisms ranging from microscopic life forms to giant trees and animals, but also their genetic differences and the diverse ecosystems they form.
3. It includes the complex interconnections among organisms and their physical environment that sustain life and keep nature stable.

**Answer:** Biodiversity encompasses the immense variety of living organisms, their genetic differences, the ecosystems they form, and their interconnections with the environment.

> Common mistake: Restricting biodiversity only to animals or plants while forgetting microorganisms and ecological interactions.

### Question 8

*3 marks · Short answer*

If you find a new organism in a pond, what features will you observe to classify it and why?

**Solution**

1. First, observe cell type and cellular organisation to determine if the organism is prokaryotic or eukaryotic, and unicellular or multicellular.
2. Next, check for the presence or absence of a cell wall and the mode of nutrition to decide whether it is autotrophic or heterotrophic.
3. These features help place the organism into the correct kingdom such as Monera, Protista, Fungi, Plantae, or Animalia.

**Answer:** We observe cell type, presence of a cell wall, level of organisation, and mode of nutrition to correctly classify the organism into its respective kingdom.

> Common mistake: Classifying organisms based only on habitat or locomotion instead of fundamental cellular and nutritional features.

### Question 9

*3 marks · Short answer*

Why do genetic studies provide deep information about living beings?

**Solution**

1. Every living cell contains genetic material in the form of DNA, which carries instructions for its growth, functioning, and inherited traits.
2. Comparing DNA sequences allows scientists to determine how closely related different organisms are to one another.
3. Similarities in DNA help trace evolutionary relationships and establish common ancestry among organisms more accurately than visible features alone.

**Answer:** Genetic studies compare DNA level instructions, helping scientists accurately determine common ancestry, evolutionary relationships, and similarities among living beings.

> Common mistake: Confusing genetic material with external morphological features.

### Question 10

*3 marks · Short answer*

How can changes in climate affect the biodiversity?

**Solution**

1. Climate change alters temperature, rainfall patterns, and natural habitats across different regions of the Earth.
2. Many species fail to adapt quickly enough to these rapid environmental changes, leading to habitat loss, decline in population, and risk of extinction.
3. Since organisms are interconnected in food webs, the disappearance or decline of one species negatively impacts other species that depend on it, reducing overall biodiversity.

**Answer:** Climate change alters habitats and weather conditions, causing habitat loss, species extinction, and disruption of ecological interconnections.

> Common mistake: Stating that climate change only affects plants without mentioning its cascading effect on animals and entire food webs.

## Revise, Reflect, Refine (Page 249)

### Question 1

*1 mark · MCQ*

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 which confirms that it is an insect.

- Bilateral symmetrical body
- Body with jointed legs
- Cylindrical body
- Body with little segmentation

**Solution**

1. Insects are arthropods characterized by having jointed appendages and legs.
2. An earthworm belongs to annelids and lacks jointed legs.

**Answer:** (ii) Body with jointed legs

> Common mistake: Confusing annelids with arthropods due to segmentation.

### Question 2

*1 mark · MCQ*

Sponges represent one of the simplest animal body plans. Their bodies lack true tissues and organs. Which feature of sponge cells supports its classification under the animal kingdom?

- Absence of mitochondria
- Ability to photosynthesise
- Presence of a cell membrane
- Presence of a cell wall

**Solution**

1. Sponges belong to the animal kingdom, and animal cells lack a rigid cell wall.
2. Instead, animal cells possess a cell membrane, distinguishing them from plants, fungi, and most bacteria which have cell walls.

**Answer:** (iii) Presence of a cell membrane

> Common mistake: Students often confuse the absence of a cell wall with the presence of a cell wall or mistakenly think animal cells lack a cell membrane.

### Question 3

*3 marks · Short answer*

Observe two different animals in your immediate environment. What features help you distinguish between them? How do these features help place them into different groups?

**Solution**

1. Animals in the immediate environment, such as a cat and a pigeon, can be distinguished using external features like body covering and locomotion.
2. The cat has hair and walks on four limbs, placing it under mammals, whereas the pigeon has feathers and wings for flight, placing it under birds.
3. These external and structural features help group organisms into systematic biological categories.

**Answer:** Animals are distinguished based on external features, body coverings, and modes of locomotion, which place them into different groups.

> Common mistake: Listing only names of animals without stating the distinguishing features.

### Question 4

*3 marks · Short answer*

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

**Solution**

1. Cellular organisation applies to all living organisms across kingdoms to distinguish prokaryotes from eukaryotes and unicellular from multicellular forms.
2. Xylem and phloem are specialized vascular tissues found only in certain plant groups like pteridophytes, gymnosperms, and angiosperms.
3. Therefore, cellular organisation is a more fundamental characteristic as it is universal, unlike vascular tissues which are absent in many organisms.

**Answer:** Cellular organisation is fundamental because it applies to all living forms, whereas vascular tissues are restricted to specific plant groups.

> Common mistake: Confining fundamental characteristics to plant-specific traits.

### Question 5

*3 marks · Short answer*

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

**Solution**

1. The organism is single-celled and possesses a well-defined membrane-bound nucleus, making it a eukaryotic unicellular organism.
2. It moves using multiple cilia, which are characteristic locomotory structures of certain aquatic protists.
3. Therefore, it most likely belongs to Kingdom Protista.

**Answer:** It belongs to Kingdom Protista because it is a unicellular eukaryote with cilia.

> Common mistake: Placing unicellular eukaryotes under Monera instead of Protista.

### Question 6

*3 marks · Short answer*

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

**Solution**

1. Biodiversity ensures that different organisms perform specific ecological roles such as producers, consumers, and decomposers.
2. Interactions like pollination, predation, and nutrient recycling maintain energy flow and stability within the ecosystem.
3. If one species disappears, dependent organisms are affected, demonstrating how diversity sustains natural balance.

**Answer:** Diversity of organisms maintains balance and stability through interconnected ecological roles like producers, consumers, and decomposers.

> Common mistake: Ignoring the functional roles of different organisms in an ecosystem.

### Question 7

*3 marks · Short answer*

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

**Solution**

1. Grouping all unicellular organisms into a single kingdom would ignore fundamental differences in cell structure and organisation.
2. It would group together prokaryotes (such as bacteria) which lack a true membrane-bound nucleus and eukaryotes (such as Amoeba and Paramecium) which have a well-defined nucleus.
3. Such a system would fail to reflect evolutionary relationships and cellular complexity, making systematic study difficult.

**Answer:** Grouping all unicellular organisms together would ignore major cellular differences like prokaryotic and eukaryotic structures.

> Common mistake: Confusing cell type (prokaryote vs eukaryote) with the number of cells (unicellular vs multicellular).

### Question 8

*3 marks · Short answer*

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

**Solution**

1. Viruses are not placed in any of the five kingdoms because they lack cellular organisation.
2. They do not have cells, cell membranes, or cytoplasm of their own.
3. They remain inactive outside a host cell and only show characteristics of living organisms when inside a living host.

**Answer:** Viruses are excluded from the five kingdom system because they lack cellular organisation and are inactive outside a host.

> Common mistake: Stating that viruses are completely non-living without mentioning their host-dependent activity.

### Question 9

*3 marks · Short answer*

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 scientific classification.

**Solution**

1. Viruses should be kept outside the five kingdom system rather than given a separate kingdom.
2. This is because kingdoms are meant for cellular life forms, whereas viruses lack cellular structure and metabolic machinery of their own.
3. This highlights the evolving nature of scientific classification, showing how new discoveries continually test and refine existing biological boundaries.

**Answer:** Viruses are kept outside the cellular classification system, demonstrating that science is an ongoing process of change and refinement.

> Common mistake: Treating viruses as simple micro-organisms belonging to Monera.

### Question 10

*3 marks · Short answer*

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

**Solution**

1. The absence of cellular organisation, cytoplasm, and independent metabolic activity prevents viruses from fitting into the five kingdom system.
2. The five kingdom classification is strictly designed for cellular organisms ranging from prokaryotes to complex eukaryotes.
3. This reveals the limitations of classification systems, showing that biological entities exist on boundaries that defy rigid, pre-defined categories.

**Answer:** Lack of cellular structure prevents viruses from fitting into classification systems, highlighting the limitations of rigid categories.

> Common mistake: Assuming that possessing genetic material alone is sufficient to place an entity within the kingdom system.

### Question 11

*3 marks · Short answer*

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

**Solution**

1. Although both bryophytes and pteridophytes lack flowers and seeds, they differ significantly in body differentiation and internal transport systems.
2. Bryophytes have a simple plant body without true roots, stems, or leaves, and lack specialised vascular tissues.
3. Pteridophytes possess true roots, stems, and leaves along with specialised vascular tissues (xylem and phloem) for transporting water and food.

**Answer:** Pteridophytes have true roots, stems, leaves, and vascular tissues, whereas bryophytes lack vascular tissues and true organs.

> Common mistake: Failing to mention the presence of vascular tissues in pteridophytes.

### Question 12

*3 marks · Short answer*

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

**Solution**

1. In the classification hierarchy, genus has fewer members but more features in common compared to class.
2. Classification moves from broad groups to specific groups, meaning lower levels share more common features.
3. A genus contains closely related species with very similar characteristics, whereas a class encompasses multiple orders with broader differences.

**Answer:** Genus has fewer members and more features in common because it is lower down in the classification hierarchy.

> Common mistake: Confusing the hierarchical order, thinking higher groups share more features.

### Question 13

*3 marks · Short answer*

A scientist discovers a new organism with the characteristic features of locomotion and autotrophic nutrition. Which character(s) would help the scientist identify the organism belonging to Protista according to the five kingdom classification?

**Solution**

1. According to the five kingdom classification, Kingdom Protista includes single-celled eukaryotic organisms.
2. To classify an organism with locomotion and autotrophic nutrition under Protista, the scientist must observe that the organism is unicellular and possesses a true, membrane-bound nucleus (eukaryotic cell structure).
3. Examples of such photosynthetic, motile unicellular protists include Euglena and Chlamydomonas.

**Answer:** The scientist must check that the organism is unicellular and eukaryotic (has a true nucleus) while exhibiting autotrophic nutrition and locomotion.

> Common mistake: Confusing unicellular protists with multicellular autotrophs like plants.

### Question 14

*3 marks · Short answer*

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

**Solution**

1. Fungi are generally multicellular, heterotrophic eukaryotes with cell walls made of chitin.
2. However, to classify a unicellular organism under Kingdom Fungi, the identification key must check for the presence of a cell wall made of chitin and a heterotrophic mode of nutrition through absorption.
3. Yeast is a classic example of a unicellular organism placed under fungi due to its chitinous cell wall and heterotrophic nutrition.

**Answer:** The key features to identify a unicellular organism as a fungus are a cell wall made of chitin and a heterotrophic (absorptive) mode of nutrition.

> Common mistake: Assuming all fungi are strictly multicellular because yeast is a notable unicellular exception.

### Question 15

*4 marks · Case-based*

During a long-term ecological study, students examined organisms collected from three different environments — a freshwater pond, damp soil near decaying logs and the digestive tract of animals. Instead of naming organisms directly, scientists recorded only structural, cellular and nutritional features as given in the table below.
[Table with organisms P, Q, R, S, T]
The students realised that some organisms fit neatly into Whittaker’s five kingdom classification, while others challenged the very basis of this classification.
Based on the case study, answer the following questions —
(i) Identify one organism that clearly belongs to the Kingdom Fungi. State one observation that supports your answer.
(ii) Which organism would be placed in the Kingdom Monera? Mention one characteristic that justifies this placement.
(iii) Organisms R and Q are both eukaryotic, yet they are placed in different kingdoms. Analyse the criteria that separate them.
(iv) Explain why organism S cannot be classified using the mode of nutrition alone.
(v) Organism T does not fit into any of the five kingdoms. Which fundamental characteristic used in classification does it lack and what does this reveal about the limitations of classification systems?
(vi) If classification were based only on habitat, which organisms might be incorrectly grouped together? Explain the scientific consequences of such a classification.
(vii) Imagine scientists discover a new organism that is multicellular, eukaryotic, lacks chlorophyll and absorbs nutrients from a host externally. Should it be placed under fungi or animalia? Justify your reasoning using classification criteria.

**Part (i)**

1. Organism Q belongs to the Kingdom Fungi.
2. It is supported by the observation that it has a multicellular, filamentous body with a cell wall, lacks chlorophyll, and grows on dead organic matter.

Answer (i): Organism Q; supported by its multicellular filamentous structure, cell wall, absence of chlorophyll, and saprophytic habit.

**Part (ii)**

1. Organism P would be placed in the Kingdom Monera.
2. It is justified by the characteristic that it is microscopic and lacks a true nucleus (prokaryotic).

Answer (ii): Organism P; justified by being microscopic and lacking a true nucleus (prokaryotic nature).

**Part (iii)**

1. Organism R is unicellular with a true nucleus and placed in Protista, while Organism Q is multicellular and filamentous with a cell wall made of chitin/cellulose placed in Fungi.
2. The criteria that separate them are the level of cellular organisation (unicellular versus multicellular) and their specific body structures and modes of nutrition.

Answer (iii): They are separated by their level of organisation (unicellular protist versus multicellular filamentous fungus) and structural features.

**Part (iv)**

1. Organism S is a multicellular vertebrate with well-differentiated tissues.
2. Classification relies on multiple fundamental criteria such as cell type, cell structure, level of organisation, and presence of a notochord or backbone, not nutrition alone since many different kingdoms share similar nutritional modes.

Answer (iv): Mode of nutrition alone is insufficient because many diverse organisms share nutritional types; classification requires structural and cellular criteria.

**Part (v)**

1. Organism T lacks cellular organisation (it is acellular).
2. This reveals the limitations of classification systems in accommodating transitional or acellular entities like viruses that possess genetic material but no cells.

Answer (v): It lacks cellular organisation, highlighting the limitation of classification systems in categorizing acellular entities like viruses.

**Part (vi)**

1. Organisms from completely different biological domains or groups living in the same habitat (such as aquatic bacteria, fish, and aquatic plants) would be incorrectly grouped together.
2. Scientifically, this would ignore fundamental differences in cell structure, genetics, and evolutionary relationships, leading to a loss of systematic understanding.

Answer (vi): Unrelated organisms sharing habitats would be grouped together, ignoring fundamental cellular and evolutionary differences.

**Part (vii)**

1. It should be placed under Fungi if it is multicellular with a cell wall absorbing nutrients, or under Animalia if it lacks a cell wall and ingests/absorbs nutrients heterotrophically.
2. The presence or absence of a rigid cell wall and the specific mode of nutrition determine its placement between these two eukaryotic kingdoms.

Answer (vii): It depends on the presence of a cell wall; if it possesses a cell wall, it goes to Fungi, otherwise to Animalia.

**Answer:** Organisms are classified based on cellular organisation, cell wall composition, and mode of nutrition, though acellular forms like viruses challenge these criteria.

> Common mistake: Confusing prokaryotic and eukaryotic features when analyzing the table rows.

## Frequently asked questions

### How many total questions and exercises are there in NCERT Class 9 Science Chapter 12?

This chapter features several embedded learning exercises across its pages, including 4 questions in Think It Over on page 228, 15 questions in Revise, Reflect, Refine on page 249, and multiple activities like Activity 12.1 and Activity 12.3. SwaVid provides complete step-by-step solutions for all these questions on this page to help students prepare thoroughly.

### Which important topics are covered in the NCERT solutions for Class 9 Science Chapter 12?

The solutions cover essential topics such as the basis of biological classification, Whittaker's Five Kingdom Classification, plant and animal diversity, and biodiversity significance. You can also find detailed answers for specific activities like microscopic observations of bacteria in Activity 12.4 and bryophytes in Activity 12.6.

### What are the hardest question types in this chapter and how should I approach them?

Case-based and analytical questions found in sections like Revise, Reflect, Refine and Activity 12.2 tend to be the most challenging. To approach them, carefully analyze the ecological interdependence and classification criteria before structuring your answers logically.

### How can I write answers for full marks in Class 9 Science Chapter 12 examinations?

To secure full marks, ensure your answers clearly define key biological terms such as biodiversity, common ancestry, and vascular tissues. Using precise scientific terminology and referencing features from the five kingdom classification will significantly improve your score.

### Is a free PDF of these NCERT solutions available for Class 9 Science Chapter 12?

Yes, a comprehensive and free PDF containing accurate NCERT solutions for this chapter is available right on this SwaVid page. Students can easily download or view the material online to support their studies for the 2026-27 academic session based on the new NCERT book.

## Related pages

- [Class 9 Science chapters](https://www.swavid.com/science/class/9)

Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student