Class 09 Biology - Patterns in Life: Diversity and Classification - Exercises

Questions and Answers

1. Meena and Hari observed an animal. Hari called it an insect while Meena said it was an earthworm. Which option confirms it is an insect?

(i) Bilateral symmetrical body (ii) Body with jointed legs (iii) Cylindrical body (iv) Body with little segmentation Answer: (ii) Body with jointed legs. (The name 'Arthropoda' literally means jointed legs, which is a defining characteristic of insects).

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2. Sponges lack true tissues and organs. Which feature 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 Answer: (Sponges are classified as animals because they are multicellular, heterotrophic, and lack a cell wall). In the context of the options provided, the absence of a cell wall (implied by being an animal) and being heterotrophic are key. (Note: Option iv is a plant/fungi feature, so its absence would support animal classification).

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3. 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) is a fundamental distinction that applies to all living organisms on Earth. In contrast, xylem and phloem are specialized tissues found only in a specific group of plants (vascular plants). Therefore, cellular structure provides a broader and more ancient basis for understanding the primary branches of life.

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4. Single-celled organism with a well-defined nucleus and multiple cilia. Which group?

Answer: It belongs to the Kingdom Protista. The presence of a well-defined nucleus makes it eukaryotic, and being single-celled is the primary criterion for Protista. Cilia are common locomotory structures in many protists (like Paramecium).

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

Answer: This would group together prokaryotic organisms (like bacteria, which lack a nucleus and organelles) with eukaryotic organisms (like amoeba or yeast, which have complex internal structures). These two groups have vastly different cellular machineries and evolutionary histories, so grouping them together would ignore the most significant biological divide in nature.

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6. Why are viruses not placed in any of the five kingdoms?

Answer: Viruses are acellular (not made of cells). They do not perform metabolic processes on their own and can only replicate inside a host cell. Since the five-kingdom system is based on cellular organization and life processes, viruses do not fit the criteria for "living" organisms in this framework.

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7. Pteridophytes vs. Bryophytes classification.

Answer: Both are non-flowering and seedless, but they differ in their level of body differentiation. Bryophytes lack true roots, stems, leaves, and vascular tissues (xylem/phloem). Pteridophytes possess true roots, stems, and leaves, and have a well-developed vascular system for conducting water and food.

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8. Which has fewer members but more features in common: Class or Genus?

Answer: Genus. In the taxonomic hierarchy (Kingdom > Phylum > Class > Order > Family > Genus > Species), as we move from Kingdom towards Species, the groups become smaller (fewer members) and the individuals within those groups share a higher degree of similarity (more common features).

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9. Case Study Observations:

(i) Identify one organism that belongs to Kingdom Fungi. Answer: Organism Q. It is multicellular, has a cell wall, lacks chlorophyll, and grows on dead organic matter (saprotrophic nutrition), which are the defining traits of fungi.

(ii) Which organism is in Kingdom Monera? Answer: Organism P. It is microscopic and has "no true nucleus" (prokaryotic), which is the primary characteristic of Monera.

(iii) Analyse the criteria separating R (Protista) and Q (Fungi). Answer: While both are eukaryotic, R is unicellular (a protist with a contractile vacuole and flagella), whereas Q is multicellular and filamentous (a fungus). They also differ in their mode of nutrition in the dark.

(iv) Why can't Organism S be classified by nutrition alone? Answer: Organism S (multicellular with a backbone) is a vertebrate animal. While it is a heterotroph, many other organisms (fungi, many protists, and all other animals) are also heterotrophs. Nutrition alone does not reveal its complex tissue differentiation or the presence of a backbone.

(v) Which characteristic does Organism T lack? Answer: Organism T (a virus) lacks cellular organisation. It is acellular and inactive outside a host. This reveals that classification systems are limited by our definitions of "life" and "cells."

(vi) Habitat-based classification consequences. Answer: If based only on habitat, a whale (mammal), a shark (fish), and a jellyfish (cnidarian) might be grouped together simply because they live in water. This would ignore their fundamental differences in anatomy, reproduction, and evolution, leading to a system with no predictive power or scientific accuracy.

(vii) Multicellular, eukaryotic, no chlorophyll, absorptive heterotroph? Answer: It should be placed under Kingdom Fungi. While animals are also heterotrophs, they typically ingest food. Fungi absorb nutrients from their environment (often after external digestion). The lack of chlorophyll and multicellular eukaryotic structure confirms it is a fungus.