Class 9 - Chapter 12: Patterns in Life: Diversity and Classification

Exercise Solution

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 which confirms that it is an insect.

Answer: (ii) Body with jointed legs

Insects belong to Phylum Arthropoda and possess jointed legs. Earthworms do not have legs. Therefore, the presence of jointed legs confirms that the animal is an insect.

2. 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?

Answer: (i) Absence of mitochondria

The correct characteristic is the absence of a cell wall. Sponges are animals and animal cells do not possess cell walls.

3. 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?

Example: Dog and Butterfly

• Dog has a backbone, four legs and internal skeleton.
• Butterfly has jointed legs, wings and an exoskeleton.

The dog is classified under Vertebrata, while the butterfly belongs to Arthropoda. Features such as body symmetry, skeleton type and presence of backbone help classify organisms into different groups.

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

Cellular organisation is a basic characteristic present in all organisms. It indicates whether an organism is prokaryotic or eukaryotic and whether it is unicellular or multicellular. Xylem and phloem are specialised tissues found only in higher plants. Therefore, cellular organisation is a more fundamental criterion for classification.

5. You find an unlabeled 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.

The organism most likely belongs to Kingdom Protista.

Reasons:

• It is unicellular.
• It possesses a true nucleus, indicating it is eukaryotic.
• Cilia are characteristic locomotory structures found in many protists such as Paramecium.

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

Biodiversity maintains ecological balance by ensuring food chains, nutrient cycling and energy flow. Different organisms perform different roles such as producers, consumers and decomposers. Greater diversity increases ecosystem stability and resilience against environmental changes.

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

Many unicellular organisms differ greatly in cellular organisation. Some are prokaryotic while others are eukaryotic. Grouping them together would ignore fundamental differences in structure, reproduction and evolution, making classification inaccurate.

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

Viruses are neither completely living nor non-living. They lack cellular organisation and can reproduce only inside a host cell. Since the five-kingdom classification is based on cellular organisation, viruses do not fit into any kingdom.

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.

A separate category for viruses may be created because they possess genetic material and show some characteristics of living organisms. However, they differ fundamentally from cellular organisms. Their unique nature justifies a separate classification rather than placement in existing kingdoms.

10. 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?

Viruses lack:

• Cellular structure
• Independent metabolism
• Independent reproduction

This shows that classification systems may not perfectly accommodate all forms of life and must evolve as scientific knowledge increases.

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

Bryophytes:

• Lack vascular tissues.
• Have rhizoids instead of true roots.
• Usually grow in moist habitats.

Pteridophytes:

• Possess vascular tissues (xylem and phloem).
• Have true roots, stems and leaves.
• Show better adaptation to land.

Thus, the presence of vascular tissues distinguishes pteridophytes from bryophytes.

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

Genus has fewer members but more features in common.

As we move from kingdom to species, the number of organisms decreases while similarities increase. Genus is a lower category than class and therefore contains fewer but more closely related organisms.

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

The scientist should check whether the organism:

• Is unicellular.
• Has a true nucleus.
• Shows both autotrophic and heterotrophic modes of nutrition.
• Possesses locomotory structures such as flagella.

These characteristics are typical of Protista.

14. 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 Kingdom Fungi?

The organism should:

• Be eukaryotic.
• Have a cell wall.
• Be heterotrophic and absorb nutrients from dead organic matter.
• Lack chlorophyll.

A unicellular fungus such as yeast satisfies these criteria.

15. Case Study

(i) Identify one organism that clearly belongs to the Kingdom Fungi. State one observation that supports your answer.

Answer: Organism Q

Observation: It grows on dead organic matter and lacks chlorophyll.

(ii) Which organism would be placed in Kingdom Monera? Mention one characteristic that justifies this placement.

Answer: Organism P

Characteristic: It lacks a true nucleus (prokaryotic).

(iii) Organisms R and Q are both eukaryotic, yet they are placed in different kingdoms. Analyse the criteria that separate them.

Q belongs to Fungi because it is multicellular, lacks chlorophyll and obtains food saprophytically.

R belongs to Protista because it is unicellular, eukaryotic and capable of both autotrophic and heterotrophic nutrition.

(iv) Explain why organism S cannot be classified using the mode of nutrition alone.

Organism S is a vertebrate animal. Classification based only on nutrition would ignore important characteristics such as body organisation, backbone, tissues and evolutionary relationships. Therefore, nutrition alone is insufficient.

(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?

Organism T lacks cellular organisation.

This shows that classification systems may not accommodate all biological entities and need modification as scientific understanding advances.

(vi) If classification were based only on habitat, which organisms might be incorrectly grouped together? Explain the scientific consequences of such a classification.

Organisms R and S may be grouped together because both are associated with aquatic environments.

However, R is a protist while S is an animal. Such classification would ignore fundamental differences in cellular organisation and evolutionary relationships, leading to inaccurate scientific conclusions.

(vii) Imagining 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 animal? Justify.

The organism should be placed under Kingdom Fungi.

Justification:

• It is eukaryotic.
• It lacks chlorophyll.
• It obtains nutrients by absorption.
• This mode of nutrition is characteristic of fungi.

Animals ingest food internally, whereas fungi absorb nutrients from external sources.