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

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Patterns in Life: Diversity and Classification – NCERT Solutions Class 9 Science Exploration includes all the questions with solutions given in NCERT Class 9 Science Exploration textbook.

NCERT Solutions Class 9

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Patterns in Life: Diversity and Classification – NCERT Solutions

Q.1: What do you understand by biodiversity?

Solution: Biodiversity refers to the variety of living organisms found on Earth, including plants, animals and microorganisms. It also includes the ecosystems in which these organisms live. Biodiversity exists at three levels: genetic diversity, species diversity and ecosystem diversity. It is important because it maintains ecological balance and supports life processes such as food chains, nutrient cycling and environmental stability.

Q.2: How does the grouping of organisms help us understand diversity?

Solution: Grouping of organisms, known as classification, helps in organising the vast diversity of living beings into smaller, manageable categories based on similarities and differences. This makes it easier to study and identify organisms. It also helps in understanding evolutionary relationships and patterns among different groups. Thus, classification simplifies the study of biodiversity and provides a systematic way to understand the variety of life on Earth.

Q.3: On what basis, are plants and animals classified?

Solution: Plants and animals are classified based on similarities and differences in their characteristics. These include cell structure, body organisation and mode of nutrition. Plants are classified by features like vascular tissues and seeds, while animals are grouped based on body structure and level of organisation.

Q.4: How does classification help address problems in farming?

Solution: Classification helps in identifying different crop plants, pests and useful organisms. By grouping them based on characteristics, farmers can select suitable crops, recognise harmful pests and apply proper control methods. It also helps in improving crop yield and managing agricultural practices effectively.

Q.5: If many organisms share common features, could they also share a common ancestry?

Solution: Yes, organisms that share many common features are likely to have a common ancestry. Similar characteristics indicate that they may have evolved from a common ancestor over time. The more features they share, the closer their evolutionary relationship, which helps in understanding the process of evolution and diversity.

Q.6: 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?

Solution: A single-celled organism carries out all life processes within one cell using specialised organelles. Each organelle performs a specific function, such as respiration, digestion and excretion. In multicellular organisms, these functions are divided among many specialised cells and tissues. Thus, while multicellular organisms require many cells for efficiency, a unicellular organism can perform all functions within a single cell due to its simpler organisation.

Q.7: Which plant features reduce their dependence on water but still require moist conditions?

Solution: Plants that show reduced dependence on water but still require moist conditions possess features such as a thin cuticle, poorly developed vascular tissues, and rhizoids instead of true roots. They lack well-developed conducting systems, so water absorption and transport occur mainly by diffusion. These plants (like bryophytes) also need water for reproduction, as male gametes must swim to reach the female gametes. Hence, they are found in moist and shady environments.

Q.8: Why do taller plants need specialised transport tissues?

Solution: Taller plants need specialised transport tissues because simple diffusion is too slow to carry water, minerals, and food over long distances. As plant size increases, cells are located far from the source of nutrients. Therefore, specialised tissues like xylem (for water and minerals) and phloem (for food transport) are required to efficiently distribute substances throughout the plant. This ensures proper growth, survival, and functioning of all parts of the plant.

Q.9: How do seeds and fruits affect where and how plants can survive?

Solution: Seeds and fruits help plants survive by aiding in protection, dispersal, and germination. The seed coat protects the embryo, while fruits assist in dispersal through wind, water, or animals. This allows plants to grow in new and suitable habitats, reducing competition with the parent plant. Seeds can also remain dormant during unfavorable conditions and germinate when conditions become suitable, ensuring the survival and spread of the plant species.

Q.10: 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.

Options:
(1) Bilateral symmetrical body
(2) Body with jointed legs ✅
(3) Cylindrical body
(4) Body with little segmentation

Explanation: Insects are identified by the presence of jointed legs and a segmented body divided into head, thorax, and abdomen. Earthworms, on the other hand, have a cylindrical body without jointed legs. Therefore, the presence of jointed legs confirms that the organism is an insect.

Q.11: 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?

Options:
(1) Absence of mitochondria
(2) Ability to photosynthesise
(3) Presence of a cell membrane ✅
(4) Presence of a cell wall

Explanation: Sponges are placed in the animal kingdom because their cells have a cell membrane and lack a cell wall, which is a defining feature of animals. They are heterotrophic and do not perform photosynthesis. Although they have a simple body plan without true tissues and organs, these cellular features confirm their classification under Kingdom Animalia.

Q.12: 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?

Solution: Two animals in our surroundings, such as a dog and a sparrow, can be distinguished based on features like body covering, limbs, and mode of movement. A dog has hair, four legs, and walks, while a sparrow has feathers, wings, and flies.

These differences help in classification by grouping animals with similar features together. For example, dogs are placed under mammals, while sparrows are classified as birds (Aves). Thus, observable characteristics help in identifying and placing organisms into different groups.

Q.13: 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?

Solution: A scientist would prefer cellular organisation as a fundamental basis of classification because it is a basic and universal feature present in all living organisms. It helps distinguish organisms into major groups like prokaryotes and eukaryotes or unicellular and multicellular forms.

In contrast, the presence of xylem and phloem is a specific feature found only in higher plants. Therefore, cellular organisation reflects deeper evolutionary relationships and provides a more fundamental and broad basis for classification.

Q.14: 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.

Solution: The organism most likely belongs to the Kingdom Protista.

This is because it is single-celled (unicellular) and has a well-defined nucleus, indicating that it is a eukaryote. The presence of cilia suggests that it uses them for movement, which is a characteristic feature of many protists (e.g., Paramecium). Therefore, these features place it under the group Protista in the five kingdom classification system.

Q.15: How does the diversity of organisms contribute to the balance and stability of an ecosystem?

Solution: The diversity of organisms helps maintain the balance and stability of an ecosystem by ensuring that different species perform varied roles such as producers, consumers, and decomposers. This creates a food web that maintains energy flow and nutrient cycling.

Greater biodiversity increases the ability of an ecosystem to withstand environmental changes, as the loss of one species can be compensated by others. Thus, biodiversity ensures the proper functioning and long-term stability of ecosystems.

Q.16: If all unicellular organisms were grouped into a single kingdom, what problems would arise?

Solution: If all unicellular organisms were placed in a single kingdom, it would ignore important differences in cellular organisation. For example, prokaryotic organisms (like bacteria) lack a true nucleus, while eukaryotic organisms (like Amoeba) have a well-defined nucleus.

They also differ in mode of nutrition, cell structure, and reproduction. Grouping them together would make classification unnatural and less meaningful, as it would not reflect their true evolutionary relationships.

Q.17: Viruses were studied in earlier classes. Why are they not placed in any of the five kingdoms? Give reasons.

Solution: Viruses are not placed in any of the five kingdoms because they do not exhibit characteristics of living organisms completely. They are acellular (not made of cells) and lack cellular organisation, which is a basic criterion for classification in the five-kingdom system.

They behave like non-living entities outside a host, as they do not carry out metabolism independently. However, inside a living host, they show living characteristics by reproducing. Due to this borderline nature between living and non-living, they are not included in any kingdom.

Q.18: 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.

Solution: I would prefer to keep viruses outside the five kingdom classification, rather than placing them in a separate kingdom. This is because viruses are acellular and do not show all characteristics of living organisms. They are inactive outside a host and become active only inside living cells, which makes them different from all other organisms included in the five kingdoms.

This situation indicates that scientific classification is not fixed but evolves over time. As new information and discoveries are made, classification systems are revised and improved to better reflect the true nature and relationships of organisms.

Q.19: 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?

Solution: Viruses cannot be placed in the five kingdom system because they lack cellular organisation and are acellular. They do not have cytoplasm or organelles and cannot carry out metabolic activities independently. Outside a host, they behave like non-living particles, while inside a host, they reproduce like living organisms.

This shows that classification systems have limitations, as they may not accommodate organisms with mixed or unique characteristics. It also highlights that classification is constantly evolving with new scientific knowledge.

Q.20: Both pteridophytes and bryophytes lack flowers and seeds, yet they are placed in different groups. Explain this classification using their key features.

Solution: Although both bryophytes and pteridophytes lack flowers and seeds, they are placed in different groups due to differences in body organisation and vascular tissues.

Bryophytes are non-vascular plants; they do not have specialised tissues like xylem and phloem and possess simple structures with rhizoids instead of true roots. In contrast, pteridophytes have well-developed vascular tissues (xylem and phloem) and true roots, stems, and leaves.

Thus, the presence or absence of vascular tissues is a key feature used to classify them into separate groups.

Q.21: In the classification hierarchy, which group - class or genus - has fewer members but more features in common? Explain your answer.

Solution: In the classification hierarchy, a genus has fewer members but more features in common than a class.

This is because classification proceeds from broader groups to more specific ones. A class contains many different organisms with fewer similarities, while a genus includes closely related species that share a large number of characteristics.

Thus, as we move from class to genus, the number of organisms decreases but the similarity among them increases.

Q.22: 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?

Solution: To identify the organism as belonging to Kingdom Protista, the scientist should look for unicellular organisation and a well-defined nucleus (eukaryotic cell).

Although the organism shows locomotion and autotrophic nutrition (like Euglena), these features alone are not sufficient. The key identifying characters of protists are that they are single-celled eukaryotes, often showing both plant-like and animal-like features.

Thus, the presence of a unicellular, eukaryotic body structure would confirm its placement in Protista.

Q.23: 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?

Solution: To classify a unicellular organism under Kingdom Fungi, the key identifying features should include heterotrophic nutrition (saprophytic or parasitic) and the presence of a cell wall made of chitin.

Although most fungi are multicellular, some (like yeast) are unicellular eukaryotes. Unlike protists, fungi do not perform photosynthesis and absorb nutrients from organic matter.

Thus, a eukaryotic, unicellular organism with chitinous cell wall and heterotrophic mode of nutrition can be placed in Kingdom Fungi.

Q.24: 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 -

Identify one organism that clearly belongs to the Kingdom Fungi. State one observation that supports your answer.
Which organism would be placed in the Kingdom Monera? Mention one characteristic that justifies this placement.
Organisms R and Q are both eukaryotic, yet they are placed in different kingdoms. Analyse the criteria that separate them.
Explain why organism S cannot be classified using the mode of nutrition alone.
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?
If classification were based only on habitat, which organisms might be incorrectly grouped together? Explain the scientific consequences of such a classification.
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.

Solution:

Organism Q belongs to Kingdom Fungi.
It shows saprophytic nutrition (grows on dead organic matter), which is a key feature of fungi.
Organism P is placed in Kingdom Monera.
It lacks a true nucleus (prokaryotic cell), which is the main characteristic of Monera.
Although both R and Q are eukaryotic: Thus, cellularity and mode of nutrition separate them.
- R is unicellular and shows both autotrophic and heterotrophic nutrition → placed in Protista
- Q is multicellular and shows saprophytic heterotrophic nutrition → placed in Fungi
Organism S cannot be classified based only on nutrition because many organisms share similar feeding habits.
Instead, features like multicellular body, presence of backbone, and tissue organisation are more reliable for placing it in Kingdom Animalia.
Organism T lacks cellular organisation (it is acellular).
This shows that classification systems have limitations, as they cannot accommodate entities like viruses that show both living and non-living characteristics.
If classification were based only on habitat, organisms like P (extreme environments) and Q (damp soil) or others from similar environments might be grouped together incorrectly. This would ignore cell structure, organisation, and evolutionary relationships, making classification unscientific and misleading.
The new organism should be placed under Kingdom Fungi.
This is because it is eukaryotic, multicellular, lacks chlorophyll, and shows absorptive heterotrophic nutrition, which are defining features of fungi, not animals (which ingest food).