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

Step-by-step working for every question of End-of-chapter exercises in NCERT's Class 9 Science book, chapter “Patterns in Life: Diversity and Classification”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.

1. Exercises Q1

   Hari says an animal in the garden is an insect; Meena says it is an earthworm. Which feature confirms an insect? (i) bilaterally symmetrical body (ii) jointed legs (iii) cylindrical body (iv) little segmentation

   1. Insects belong to the arthropod group, which is defined by having jointed appendages.
   2. Earthworms have cylindrical bodies with segments but lack jointed legs.
   3. Thus, jointed legs are the feature that confirms the animal is an insect.

   Answer: (ii)

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2. Exercises Q2

   Sponges have no true tissues or organs. Which feature of their cells supports placing them in the animal kingdom? (i) no mitochondria (ii) can photosynthesise (iii) a cell membrane (iv) a cell wall

   1. (i) Sponges are classified as animals because their cells are eukaryotic and lack a rigid cell wall.
   2. (ii) The presence of a cell membrane is a key feature of animal cells, distinguishing them from plants and fungi which have cell walls.
   3. (iii) Options like photosynthesis or absence of mitochondria do not apply to sponges, as they are heterotrophic and have mitochondria.

   Answer: (iii) Presence of a cell membrane

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3. Exercises Q3

   Take two different animals around you. What features tell them apart, and how do these features put them in different groups?

   1. Choose two animals, such as a house cat and a parrot, that are commonly found around you.
   2. Identify visible external features like body covering, limb structure, and size to distinguish them.
   3. Note that the cat has fur and walks on four legs, while the parrot has feathers and wings for flight.
   4. These features place them in different groups because classification uses broad visible traits to organise organisms.
   5. The cat belongs to the mammal group due to fur and mammary glands, while the parrot is a bird due to feathers.

   Answer: External features like body covering and limbs distinguish the animals, placing them in different groups such as mammals and birds based on classification criteria.

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4. Exercises Q4

   Why would a scientist choose cellular organisation, rather than the presence of xylem and phloem, as a more basic feature for classification?

   1. Cellular organisation is a fundamental feature present in all living organisms, distinguishing them from non-living entities.
   2. Xylem and phloem are specific vascular tissues found only in certain plant groups, not in all organisms.
   3. Using cellular organisation allows for the broad classification of all life forms into kingdoms based on basic structural differences.
   4. Relying on xylem and phloem would exclude most organisms, such as animals, fungi, and non-vascular plants, from the classification system.

   Answer: Cellular organisation is chosen because it is a universal basic feature of all life, whereas xylem and phloem are specific to only certain plants, making cellular organisation a more fundamental and inclusive criterion for classification.

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5. Exercises Q5

   An unlabelled slide shows a single-celled organism with a well-defined nucleus and many cilia. Which group is it most likely in? Why?

   1. The presence of a well-defined nucleus indicates that the organism is eukaryotic, which excludes it from the Kingdom Monera.
   2. The fact that it is a single-celled organism places it in the Kingdom Protista, which includes unicellular eukaryotes.
   3. The presence of multiple cilia is a specific feature of certain protists like Paramecium, confirming its classification within this group.

   Answer: The organism belongs to the Kingdom Protista because it is a unicellular eukaryote with a well-defined nucleus and cilia.

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6. Exercises Q6

   How does the diversity of organisms help keep an ecosystem balanced and stable?

   1. Every organism in an ecosystem performs a specific function that supports the overall stability of nature.
   2. Microscopic algae release oxygen, while fungi and bacteria break down waste to make soil fertile.
   3. Animals like birds and bees help in pollination, and plants produce food that sustains other life forms.
   4. These interconnections between different organisms ensure that ecosystems remain balanced and functional.

   Answer: Diversity keeps ecosystems stable because each organism plays a unique role, such as producing oxygen, decomposing waste, or pollinating, and these interconnections sustain the balance of nature.

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7. Exercises Q7

   What problems would arise if all unicellular organisms were put in one kingdom?

   1. Unicellular organisms include both prokaryotes like bacteria and eukaryotes like amoeba.
   2. Bacteria lack a membrane-bound nucleus while eukaryotes have a true nucleus.
   3. Grouping them together would mix organisms with fundamentally different cellular structures.
   4. This would make it difficult to study their distinct evolutionary relationships and characteristics.

   Answer: Mixing prokaryotes and eukaryotes in one kingdom would obscure key structural differences and hinder systematic study.

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8. Exercises Q8

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

   1. The five kingdom classification groups organisms based on cellular organisation and other common features.
   2. Viruses lack cellular organisation, which is a fundamental requirement for placement in any of the five kingdoms.
   3. Because they do not have cells, viruses cannot be classified under Monera, Protista, Fungi, Plantae, or Animalia.

   Answer: Viruses are not placed in any of the five kingdoms because they lack cellular organisation, which is a basic criterion for classification in this system.

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9. Exercises Q9

   If you revised the five kingdom classification, would you make a separate group for viruses or keep them outside? Justify, and say what this shows about how classification changes.

   1. Viruses lack cellular organisation, which is the fundamental basis for the five kingdom classification system.
   2. Since viruses do not have cells, they cannot be grouped into any of the existing kingdoms like Monera or Protista.
   3. Keeping them outside the system is more appropriate because they do not fit the criteria of being living, cellular organisms.
   4. This situation shows that classification systems are not static and must evolve as new scientific knowledge is discovered.
   5. It indicates that scientific classification is dynamic and changes to accommodate new findings about organisms.

   Answer: (i) Keep them outside the system because they lack cellular organisation; (ii) This shows that classification is dynamic and evolves with new scientific knowledge.

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10. Exercises Q10

    Viruses have genetic material but no cells. Which features keep them out of the five kingdoms, and what does this show about the limits of classification?

    1. Viruses lack cellular organisation, which is a fundamental requirement for all five kingdoms.
    2. They are described as acellular and contain genetic material but remain inactive outside a host cell.
    3. The five kingdom system groups organisms based on cell type, nutrition, and other cellular features that viruses do not possess.
    4. This shows that classification systems have limitations when dealing with entities that do not fit standard biological definitions.

    Answer: Viruses are excluded because they lack cellular organisation and are acellular; this reveals that classification systems are limited by their reliance on cellular characteristics.

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11. Exercises Q11

    Pteridophytes and bryophytes both lack flowers and seeds, yet sit in different groups. Explain using their key features.

    1. (i) Bryophytes lack true roots, stems, and leaves, as well as vascular tissues for transport.
    2. (ii) Pteridophytes possess true roots, stems, and leaves along with vascular tissues like xylem and phloem.
    3. (iii) The presence of these structural and transport features in pteridophytes distinguishes them from bryophytes.
    4. (iv) Both groups depend on water for reproduction and do not produce seeds, but their body organisation differs.

    Answer: (i) Bryophytes lack true roots, stems, leaves, and vascular tissues; (ii) Pteridophytes have true roots, stems, leaves, and vascular tissues; (iii) These structural differences place them in different groups despite both lacking flowers and seeds.

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12. Exercises Q12

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

    1. Genus has fewer members than class because it is a smaller, more specific group in the hierarchy.
    2. Genus has more features in common because organisms in the same genus share detailed characteristics.
    3. Class is a broader group containing multiple genera, so it has more members but fewer shared specific features.

    Answer: Genus has fewer members but more features in common than class.

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13. Exercises Q13

    A new organism can move and makes its own food. Which features would place it in Protista under the five kingdom classification?

    1. According to the five kingdom classification, the kingdom Protista is defined by organisms that are mostly unicellular and possess a true nucleus.
    2. Although the organism moves and makes its own food, these features alone are not sufficient to place it in Protista as plants are also autotrophic.
    3. The key distinguishing character that would identify this organism as belonging to Protista is that it is unicellular with a true nucleus.

    Answer: The character that helps identify the organism as belonging to Protista is that it is unicellular and has a true nucleus.

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14. Exercises Q14

    A unicellular eukaryote is identified as a fungus. What identification key would you suggest for keeping a unicellular organism in Kingdom Fungi?

    1. Check if the organism has a true nucleus to confirm it is eukaryotic.
    2. Verify that the cell wall is made of chitin, which is a key feature of fungi.
    3. Observe that the organism does not make its own food and is heterotrophic.
    4. Note that it absorbs nutrients from dead or decaying matter rather than ingesting them.

    Answer: The identification key includes having a chitin cell wall, being heterotrophic, and absorbing nutrients from decaying matter.

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15. Exercises Q15

    Organisms by features: P microscopic, no true nucleus, rigid covering, survives salt and heat; Q multicellular filaments, cell wall, no chlorophyll, lives on dead matter; R unicellular, true nucleus, flagella, photosynthesises in light, feeds in the dark; S multicellular, backbone, breathes in water when young; T acellular, genetic material, inactive outside a host. (i) Which is a fungus? (ii) Which is in Monera? (iii) What separates R and Q? (iv) Why can S not be classified by nutrition alone? (v) What does T lack, and what does it show? (vi) What goes wrong if grouped by habitat only? (vii) A new multicellular eukaryote without chlorophyll absorbs food from a host: fungi or animals?

    1. (i) Q is a fungus because it is multicellular, has a cell wall, lacks chlorophyll, and grows on dead organic matter as a saprophyte.
    2. (ii) P belongs to Monera because it is microscopic, lacks a true nucleus, and has a rigid cell covering, which are features of prokaryotes.
    3. (iii) R is separated from Q because R is a unicellular eukaryote in Protista, while Q is a multicellular eukaryote in Fungi.
    4. (iv) S cannot be classified by nutrition alone because it is an animal that moves and has a backbone, distinguishing it from plants despite its aquatic respiration.
    5. (v) T lacks a cellular structure and is inactive outside a host, showing it is a virus which is acellular and depends on a host for life processes.
    6. (vi) Grouping by habitat only causes confusion because organisms like Amoeba and bacteria share habitats but differ greatly in cell structure and nutrition.
    7. (vii) The new organism is a fungus because it is a multicellular eukaryote without chlorophyll that absorbs food, fitting the fungal kingdom criteria.

    Answer: (i) Q; (ii) P; (iii) R is unicellular eukaryote, Q is multicellular eukaryote; (iv) S is an animal with a backbone; (v) T lacks cells and shows viral nature; (vi) It ignores cellular and nutritional differences; (vii) Fungi

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