Class 9 › Science › Exploration Patterns in Life: Diversity and Classification Class 9 Science · Exploration · Chapter 12
Practice all → Summary Questions & answers Practise this chapter → This chapter explores the enormous variety of life (biodiversity) and the need to organise it through classification. The Earth holds countless life forms, each playing a role in keeping ecosystems stable, and humans depend on this diversity for food, medicine and livelihoods. Because there are so many organisms, scientists classify them — sorting them into groups based on shared characteristics — which makes study easier, shows relationships and helps in farming and conservation. Classification is hierarchical: organisms are grouped into ever larger categories — species, genus, family, order, class, phylum (or division in plants) and kingdom — with species being the basic unit. Early systems sorted living things into just plants and animals, but this was inadequate, so Whittaker proposed a five-kingdom system based on cell type (prokaryotic or eukaryotic), body organisation (unicellular or multicellular) and mode of nutrition: Monera (prokaryotes such as bacteria), Protista (single-celled eukaryotes such as amoeba and algae), Fungi (decomposers that absorb food, such as moulds and mushrooms), Plantae (multicellular photosynthetic plants) and Animalia (multicellular organisms that ingest food). To name organisms unambiguously across languages, Carl Linnaeus introduced binomial nomenclature, giving each species a two-part Latin scientific name (genus + species), such as Homo sapiens or Mangifera indica. The chapter shows how classification reflects evolutionary relationships and supports work in agriculture, medicine and the conservation of biodiversity.
Biodiversity
The immense variety of living organisms found on the Earth, from microbes to large plants and animals, across many habitats.
Classification
The arrangement of organisms into groups based on shared characteristics, to make their study easier and show relationships.
Species
The basic unit of classification — a group of similar organisms that can interbreed and produce fertile offspring.
Five-kingdom system
Whittaker’s scheme dividing life into Monera, Protista, Fungi, Plantae and Animalia, based on cell type, organisation and nutrition.
Binomial nomenclature
Linnaeus’s system of giving each species a two-word Latin scientific name made of its genus and species names.
Hierarchy of classification
The ordered ranks species, genus, family, order, class, phylum/division and kingdom, from smallest to largest group.
Q1 What is biodiversity and why is it important? Answer Q2 Why do scientists classify organisms? Answer Q3 What is the basic unit of classification? Answer Q4 Write the hierarchy of classification from smallest to largest group. Answer Q5 On what basis did Whittaker divide organisms into five kingdoms? Answer Q6 Name the five kingdoms and one feature of each. Answer Q7 How do fungi obtain their food? Answer Q8 What is binomial nomenclature and who introduced it? Answer Q9 Why is a universal scientific name needed for each organism? Answer Q10 How does classification help in agriculture and conservation? Answer Q1 What do you understand by biodiversity? Answer Q2 How does the grouping of organisms help us understand diversity? Answer Q3 On what basis, are plants and animals classified? Answer Q4 How does classification help address problems in farming? Answer Q1 1. Ponder on the questions given below: Which animals can you identify in the given picture? Answer Q2 1. Ponder on the questions given below: Where are they seen? Answer Q3 1. Ponder on the questions given below: Which animals in the picture seem active: (i) during the day? Answer Q4 1. Ponder on the questions given below: Which animals in the picture seem active: (ii) during the night? Answer Q5 1. Ponder on the questions given below: Which animals in the picture seem active: (iii) both during the day and the night? Answer Q6 2. Record your observations in Table 12.1. Answer Q7 3. Now, try grouping the same organisms in more than one way. Each time change the criterion you are using for grouping (Table 12.2). Answer Q1 1. If many organisms share common features, could they also share a common ancestry? Answer Q1 Think and discuss the case based on the following questions — (i) How can scientists keep track of so many species? Answer Q2 Think and discuss the case based on the following questions — (ii) The four hornbills look similar in some ways. What features can help scientists distinguish them from one another? Answer Q3 Think and discuss the case based on the following questions — (iii) What would happen if the large, old trees disappeared from the forest? Answer Q1 2. 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? Answer Q1 3. Which plant features reduce their dependence on water but still require moist conditions? Answer Q2 4. Why do taller plants need specialised transport tissues? Answer Q3 5. How do seeds and fruits affect, where and how plants can survive? Answer Q1 6. 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? Answer Q1 7. Does the term 'biodiversity' relate only to the variety of organisms, or does it encompass other elements? Answer Q2 8. If you find a new organism in a pond, what features will you observe to classify it and why? Answer Q3 9. Why do genetic studies provide deep information about living beings? Answer Q4 10. How can changes in climate affect the biodiversity? Answer Q1 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. (i) Bilateral symmetrical body (ii) Body with jointed legs (iii) Cylindrical body (iv) Body with little segmentation Answer Q2 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? (i) Absence of mitochondria (ii) Ability to photosynthesise (iii) Presence of a cell membrane (iv) Presence of a cell wall Answer Q3 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 Q4 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 Q5 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 Q6 6. How does the diversity of organisms contribute to the balance and stability of an ecosystem? Answer Q7 7. If all unicellular organisms were grouped into a single kingdom, what problems would arise? Answer Q8 8. Viruses were studied in earlier classes. Why are they not placed in any of the five kingdoms? Give reasons. Answer Q9 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 Q10 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 Q11 11. Both pteridophytes and bryophytes lack flowers and seeds, yet they are placed in different groups. Explain this classification using their key features. Answer Q12 12. In the classification hierarchy, which group — class or genus — has fewer members but more features in common? Explain your answer. Answer Q13 13. 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? Answer Q14 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 Q15 15. 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. Organisms Key Observations P Microscopic; no true nucleus; rigid cell covering; survives high salinity and temperature Q Multicellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter R Unicellular; true nucleus; contractile vacuole present; moves using flagella; shows photosynthesis in light but heterotrophic in the absence of light S Multicellular; well-differentiated tissues; backbone present; aquatic respiration during early life stage T Acellular; contains genetic material; remains inactive outside a host cell 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. Answer Q16 15. 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. Organisms Key Observations P Microscopic; no true nucleus; rigid cell covering; survives high salinity and temperature Q Multicellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter R Unicellular; true nucleus; contractile vacuole present; moves using flagella; shows photosynthesis in light but heterotrophic in the absence of light S Multicellular; well-differentiated tissues; backbone present; aquatic respiration during early life stage T Acellular; contains genetic material; remains inactive outside a host cell 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 — (ii) Which organism would be placed in the Kingdom Monera? Mention one characteristic that justifies this placement. Answer Q17 15. 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. Organisms Key Observations P Microscopic; no true nucleus; rigid cell covering; survives high salinity and temperature Q Multicellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter R Unicellular; true nucleus; contractile vacuole present; moves using flagella; shows photosynthesis in light but heterotrophic in the absence of light S Multicellular; well-differentiated tissues; backbone present; aquatic respiration during early life stage T Acellular; contains genetic material; remains inactive outside a host cell 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 — (iii) Organisms R and Q are both eukaryotic, yet they are placed in different kingdoms. Analyse the criteria that separate them. Answer Q18 15. 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. Organisms Key Observations P Microscopic; no true nucleus; rigid cell covering; survives high salinity and temperature Q Multicellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter R Unicellular; true nucleus; contractile vacuole present; moves using flagella; shows photosynthesis in light but heterotrophic in the absence of light S Multicellular; well-differentiated tissues; backbone present; aquatic respiration during early life stage T Acellular; contains genetic material; remains inactive outside a host cell 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 — (iv) Explain why organism S cannot be classified using the mode of nutrition alone. Answer Q19 15. 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. Organisms Key Observations P Microscopic; no true nucleus; rigid cell covering; survives high salinity and temperature Q Multicellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter R Unicellular; true nucleus; contractile vacuole present; moves using flagella; shows photosynthesis in light but heterotrophic in the absence of light S Multicellular; well-differentiated tissues; backbone present; aquatic respiration during early life stage T Acellular; contains genetic material; remains inactive outside a host cell 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 — (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 Q20 15. 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. Organisms Key Observations P Microscopic; no true nucleus; rigid cell covering; survives high salinity and temperature Q Multicellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter R Unicellular; true nucleus; contractile vacuole present; moves using flagella; shows photosynthesis in light but heterotrophic in the absence of light S Multicellular; well-differentiated tissues; backbone present; aquatic respiration during early life stage T Acellular; contains genetic material; remains inactive outside a host cell 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 — (vi) If classification were based only on habitat, which organisms might be incorrectly grouped together? Explain the scientific consequences of such a classification. Answer Q21 15. 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. Organisms Key Observations P Microscopic; no true nucleus; rigid cell covering; survives high salinity and temperature Q Multicellular; filamentous body; cell wall present; no chlorophyll; grows on dead organic matter R Unicellular; true nucleus; contractile vacuole present; moves using flagella; shows photosynthesis in light but heterotrophic in the absence of light S Multicellular; well-differentiated tissues; backbone present; aquatic respiration during early life stage T Acellular; contains genetic material; remains inactive outside a host cell 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 — (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 huge variety of living organisms found on the Earth is called:
A Heredity B Photosynthesis C Adaptation D Biodiversity
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