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

Exercise Solution

Question 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.

Correct Answer: (ii) Body with jointed legs

Explanation:

Insects belong to the phylum Arthropoda. The most characteristic feature of arthropods is the presence of jointed legs. Earthworms belong to the phylum Annelida and have a long segmented body but do not possess jointed legs. Therefore, the presence of jointed legs confirms that the animal is an insect.

Question 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?

Correct Answer: (iii) Presence of a cell membrane

Explanation:

Sponges belong to the kingdom Animalia. Although they lack true tissues and organs, their cells have a cell membrane and do not possess a cell wall. Like other animals, they are multicellular and heterotrophic.

Question 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?

Answer:

Animals can be distinguished by observing their external features such as body covering, body symmetry, number of legs, body segmentation, presence or absence of a backbone, and method of movement. These characteristics help scientists classify animals into different groups.

Example: Dog and Butterfly

Thus, differences in body structure help classify organisms into suitable taxonomic groups.

Question 4

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?

Answer:

Cellular organisation is a more fundamental characteristic because it reflects the basic structure of all living organisms. Features such as whether the organism is unicellular or multicellular and whether it has a prokaryotic or eukaryotic cell are more basic than specialised tissues.

Xylem and phloem are vascular tissues found only in certain groups of plants. These tissues evolved later and cannot be used to classify all living organisms.

Question 5

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.

Answer:

The organism most likely belongs to the Kingdom Protista.

Reasons:

• It is unicellular.
• It possesses a well-defined nucleus, indicating that it is a eukaryote.
• It has cilia, which are used for movement and feeding. Many protists, such as Paramecium, possess cilia.

Question 6

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

Answer:

Biological diversity (biodiversity) is the variety of living organisms present in an ecosystem. Each organism performs a specific role, such as producing food, consuming other organisms, decomposing dead matter, or recycling nutrients. The presence of a wide variety of organisms helps maintain ecological balance and increases the stability of ecosystems.

Greater biodiversity ensures that if one species declines, other organisms can continue performing similar ecological functions. Thus, ecosystems become more resilient to natural disturbances and environmental changes.

Question 7

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

Answer:

Grouping all unicellular organisms into one kingdom would ignore the fundamental differences among them. Unicellular organisms include both prokaryotes and eukaryotes, which differ greatly in their cellular organisation and evolutionary relationships.

Such a classification would not accurately represent the diversity of living organisms.

Conclusion:

Therefore, unicellular organisms are placed in different kingdoms such as Monera and Protista based on their cellular organisation and other characteristics.

Question 8

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

Answer:

Viruses are not included in Whittaker's Five Kingdom Classification because they do not possess all the characteristics of living organisms. They show both living and non-living characteristics.

Conclusion:

Since viruses are neither completely living nor completely non-living, they are kept outside the Five Kingdom Classification.

Question 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 scientific classification.

Answer:

I would keep viruses outside the Five Kingdom Classification because they do not satisfy the basic criteria used for classifying living organisms. Viruses are acellular, lack independent metabolism and reproduction, and become active only inside the cells of a living host.

However, scientists continue to study viruses in detail because of their unique characteristics and their importance in medicine, biotechnology and evolution. If future scientific evidence provides a better understanding of their nature, classification systems may be modified accordingly.

What does this indicate about scientific classification?

• Scientific classification is dynamic and changes with new discoveries.
• It is based on scientific evidence rather than fixed ideas.
• As knowledge about organisms increases, classification systems become more accurate and reflect evolutionary relationships more effectively.

Question 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 systems?

Answer:

Viruses possess genetic material (DNA or RNA), but they are not made up of cells. They cannot perform life processes independently and reproduce only inside the living cells of a host organism. Because the Five Kingdom Classification is based mainly on cellular organisation, mode of nutrition, body organisation and reproduction, viruses do not satisfy these criteria.

Therefore, viruses are not included in any of the five kingdoms.

What does this tell us about the limitations of classification systems?

• No classification system can perfectly classify every organism.
• Scientific classification is based on the knowledge available at a particular time.
• As new discoveries are made, classification systems are revised and improved.
• The existence of viruses shows that some organisms possess characteristics of both living and non-living things, making classification more complex.

Question 11

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

Answer:

Although both bryophytes and pteridophytes are non-flowering plants and reproduce by spores, they differ significantly in their body organisation and vascular tissues. These differences place them in separate groups.

Conclusion:

Pteridophytes possess vascular tissues and true plant organs, whereas bryophytes do not. Therefore, they are placed in different groups despite both lacking flowers and seeds.

Question 12

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

Answer:

Genus has fewer members but more characteristics in common than a class.

In biological classification, organisms are arranged from broader categories to more specific categories:

Kingdom → Phylum (Division) → Class → Order → Family → Genus → Species

As we move from kingdom towards species, the number of organisms decreases while the similarity among them increases.

Conclusion:

Since organisms in the same genus are more closely related, genus has fewer members but greater similarity than class.

Question 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?

Answer:

The scientist should examine the organism's cellular organisation and other basic characteristics. Some protists, such as Euglena, show both locomotion and autotrophic nutrition.

The following characteristics would help identify the organism as belonging to Kingdom Protista.

Example: Euglena is a unicellular protist that moves using a flagellum and can prepare its own food by photosynthesis.

Question 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 the Kingdom Fungi?

Answer:

Being unicellular alone does not place an organism in Kingdom Fungi. The researcher should examine additional characteristics that are typical of fungi.

Conclusion:

If the organism is unicellular, eukaryotic, has a chitinous cell wall, lacks chlorophyll, and obtains nutrition by absorption, it can be classified under Kingdom Fungi. Yeast is a well-known example of a unicellular fungus.

Question 15

During a long-term ecological study, students examined organisms collected from different environments. Based on the observations given in the table, answer the following questions.

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

Answer:

Organism Q belongs to the Kingdom Fungi.

Supporting Observation: It lacks chlorophyll and grows on dead organic matter, showing a saprophytic mode of nutrition, which is a characteristic feature of fungi.

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

Answer:

Organism P belongs to the Kingdom Monera.

Justification: It has no true nucleus, indicating that it is a prokaryotic organism, which is the defining feature of Kingdom Monera.

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

Answer:

Although both R and Q are eukaryotic organisms, they differ in body organisation, mode of nutrition and movement.

Therefore, despite both being eukaryotic, differences in cellular organisation, locomotion and nutrition place them in different kingdoms.

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

Answer:

Mode of nutrition alone is not sufficient for classifying an organism because classification is based on several characteristics such as cell type, body organisation, presence of tissues, backbone, method of reproduction and evolutionary relationships.

Organism S possesses a backbone, has well-differentiated tissues and undergoes aquatic respiration during its early life stage. These are important characteristics of vertebrate animals and cannot be ignored even if another organism shows a similar mode of nutrition.

(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?

Answer:

Organism T lacks the most fundamental characteristic required for classification into the five kingdoms—it is not cellular (acellular).

Since Whittaker's Five Kingdom Classification is based on cellular organisation, acellular viruses cannot be included in any kingdom.

This reveals that:

• Scientific classification has certain limitations.
• Some biological entities, such as viruses, do not satisfy all classification criteria.
• Classification systems are revised as scientific knowledge advances.

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

Answer:

If only habitat were considered, organisms living in the same environment could be grouped together even though they belong to completely different kingdoms.

For example:

• P and R may both occur in aquatic environments but belong to Monera and Protista, respectively.
• R and S may also occur in freshwater habitats, yet one is a unicellular protist while the other is a multicellular vertebrate.

Scientific Consequences:

• Evolutionary relationships would not be represented correctly.
• Organisms with very different body structures would be grouped together.
• Identification and scientific study would become inaccurate.
• The classification would fail to reflect natural relationships among organisms.

(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.

Answer:

The organism should be placed under the Kingdom Fungi.

Justification:

Animals obtain food by ingestion, whereas fungi obtain nutrients through external absorption. Therefore, the given organism shows the characteristic mode of nutrition of fungi.

Hence, it should be classified under Kingdom Fungi.