NCERT Exemplars: The Living World - 2

Long Answer Type Questions

Q.1. What is meant by living? Give any four defining features of life forms.
Ans: Living refers to those organisms that exhibit characteristics such as growth, reproduction, metabolism, responsiveness, and the ability to maintain internal balance (homeostasis).

Four defining features of life forms are:

1. Growth:
   Living organisms increase in size and mass. This growth occurs from within due to cell division.

2. Reproduction:
   Living organisms have the ability to produce new individuals of their own kind, either sexually or asexually.

3. Metabolism:
   All living organisms carry out biochemical reactions such as respiration, digestion, and excretion to maintain life.

4. Response to stimuli (Consciousness):
   Living organisms can sense and respond to environmental changes like light, temperature, and touch.

These features together help distinguish living organisms from non-living things.

Q.2. A scientist has come across a plant which he feels is a new species. How will he go about its identification, classification and nomenclature? 
Ans: When a scientist suspects that a plant is new to science, a standard, careful procedure is followed to establish its identity and to name it officially. The main steps are:

• Collection and documentation: Collect representative specimens, preferably with flowers and fruits. Record the exact locality, habitat, date and ecological notes. Prepare voucher specimens and preserve them properly for future reference.
• Characterisation: Describe morphological and anatomical features in detail (leaf shape, flower structure, fruit type, stem characters, etc.). Take clear photographs and make botanical drawings when possible.
• Comparison with known taxa: Consult regional floras, monographs, herbarium specimens and taxonomic literature to compare the plant with already described species and to check whether it is indeed undescribed.
• Use of keys and experts: Use dichotomous keys to narrow down the identity and, if required, consult specialists working on that plant group for confirmation.
• Designation of type specimen: Choose a single representative specimen as the holotype and deposit it in a recognised herbarium; isotypes or paratypes may also be deposited in other herbaria.
• Nomenclature: Propose a scientific name following the rules of the International Code of Nomenclature for algae, fungi and plants (ICN). Prepare a formal description (diagnosis) in the required language and clearly state characters that distinguish the new species from its closest relatives.
• Publication: Publish the name and description in a recognised scientific journal so the name becomes validly published and available to the scientific community.

Following these steps ensures that the new species is properly documented, comparable with existing material and validly named according to international standards.

Q.3. Brassica campestris Linn
(a) Give the common name of the plant.
(b) What do the first two parts of the name denote?
(c) Why are they written in italics?
(d) What is the meaning of Linn written at the end of the name?
Ans: 
(a) Mustard.
(b) The first word is the genus name (Brassica) and the second word is the specific epithet (campestris). Together they form the species name Brassica campestris.
(c) The two words of the scientific name are printed in italics (or underlined when handwritten) because they are Latinised scientific names; the genus name is capitalised and the specific epithet is written in lower case.
(d) Linn (short for Linnaeus) is the author citation. It indicates that Carl Linnaeus was the first to validly describe and publish this species name.

Q.4. What are Taxonomical Aids? Give the importance of herbaria and museums. How are Botanical gardens and Zoological parks useful in conserving biodiversity?
Ans: Taxonomical aids are tools, collections and reference materials that help taxonomists to identify, classify and name organisms reliably. Key taxonomical aids include botanical gardens, zoological parks, herbaria, biological museums and identification keys.

(i) Botanical gardens are living plant collections maintained for research, education and conservation. They cultivate rare, endemic and economically important plants, provide living material for study, support ex situ conservation and raise public awareness about plant diversity.

(ii) Zoological parks keep living animals under managed conditions and contribute to conservation through captive-breeding programmes, rehabilitation and reintroduction efforts. They also support behavioural and ecological research and educate the public about wildlife protection.

(iii) Herbarium is a repository of dried, pressed and systematically arranged plant specimens mounted on sheets with labels that record collection details (date, place, collector, local and scientific names). Herbaria serve as permanent records of plant diversity, provide material for identification and taxonomic studies, and house type specimens that define species names.

(iv) Biological museums preserve specimens (skeletal material, preserved animals, models and casts) and are important for teaching, reference and historical documentation. Museum collections allow comparison of morphological characters and record past biodiversity and distribution patterns.

(v) Keys (for example dichotomous keys) are analytical aids that present a series of paired contrasting statements (couplets). By following the leads, a user is guided step by step to the identity of an unknown organism.

Botanical gardens and Zoological parks are useful in conserving biodiversity

Botanical gardens and zoological parks support conservation by maintaining ex situ living collections, propagating and breeding endangered species, participating in reintroduction programmes and acting as genetic reservoirs. They provide plant and animal material for research, training and public education, and help build support for in situ conservation measures.

Importance of Herbaria and Museums

Herbaria and museums provide permanent, verifiable records of biodiversity. Herbarium sheets and museum specimens carry collection data essential for taxonomic work, biogeographic studies and conservation planning. They preserve type specimens and historical material that help resolve taxonomic problems and track changes in species distributions over time.

Q.5. Define a taxon. What is meant by the taxonomic hierarchy? Give a flow diagram from the lowest to the highest category for a plant and an animal. What happens to the number of individuals and number of shared characters as we go up the taxonomical hierarchy? 
Ans:  A taxon is a named group of organisms at any rank (for example species, genus or family) that share defining characters. Taxa are the units used in classification.

Classification arranges organisms into a series of ranked categories; these ranks together form the taxonomic hierarchy. Each higher rank includes several units of the lower rank and groups organisms by progressively broader shared features.

• Flow diagram (plant): Species → Genus → Family → Order → Class → Division → Kingdom.
• Flow diagram (animal): Species → Genus → Family → Order → Class → Phylum → Kingdom.
• As we move up the taxonomic hierarchy from species to kingdom:
  • The number of individuals included in each category increases (for example, a genus contains many species; a family contains many genera).
  • The number of shared characters common to all members of a category decreases; members of a species share many specific characters, while members of a kingdom share only a few broad features.

Q.6. A student of taxonomy was puzzled when told by his professor to look for a key to identify a plant. He went to his friend to clarify what 'Key' the professor was referring to? What would the friend explain to him?
Ans: In taxonomy, a key is an identification aid that helps determine the identity of an unknown organism. The friend would explain:

• Keys are usually presented as a series of paired contrasting statements called couplets. Each couplet presents two alternatives; choosing one alternative directs the user to the next appropriate couplet until an identification is reached.
• Keys are prepared for different taxonomic levels (family, genus, species) and are analytical in form.
• Dichotomous keys, which give two choices at each step, are commonly used. Each statement in the key is called a lead.

Q.7. Metabolism is a defining feature of all living organisms without exception. Isolated metabolic reactions in vitro are not living things but surely living reactions. Comment.
Ans: Metabolism- the organised set of chemical reactions inside living cells-is essential for life. It provides energy and raw materials for maintenance, growth and reproduction. In an organism, metabolic reactions are integrated, regulated and occur within the cellular context.

Although individual biochemical reactions can be carried out in cell-free systems in vitro, such isolated reactions lack other essential attributes of life, such as cellular organisation, coordinated regulation, growth and reproduction. Therefore, while isolated metabolic reactions resemble aspects of living processes, they are not living entities; they are biochemical events outside the organised living system.

Q.8. Do you consider a person in coma-living or dead?
Ans: A person in a coma requires careful medical assessment before deciding whether they are alive or dead. Important considerations are:

• If a person is brain-dead-that is, there is a complete and irreversible loss of all brain functions including brain-stem reflexes-then they are medically and legally regarded as dead even if some bodily functions are temporarily maintained by machines.
• If the person is in a coma but the brain-stem and vital centres still function, respiration and circulation continue and the person is considered alive, although unconscious.
• Loss of consciousness alone does not equal death; the clinical and legal determination depends on the irreversible loss of integrated brain functions.

Thus, a clear conclusion depends on medical criteria rather than on the single feature of consciousness.

Q.9. What is the similarity and dissimilarity between "whole moong daal" and "broken moong daal" in terms of respiration and growth? Based on these parameters, classify them into living or nonliving?
Ans:

Whole moong daal contains an intact embryo and is therefore viable. While dormant, its respiration rate is low; after soaking in water, respiration increases, the embryo resumes metabolic activity and the seed germinates and grows into a new plant. Hence whole moong daal is classified as living (dormant but viable).

Broken moong daal lacks an intact embryo or essential parts required for germination. It cannot germinate or grow into a plant, so it fails the criteria for growth and reproduction and is regarded as non-living for these purposes, although some chemical components may still undergo simple reactions.

Similarity: Both may show some chemical reactions such as respiration in isolated components, but only whole moong daal has the organised living embryo capable of growth and development.

Q.10. Some of the properties of tissues are not the constituents of its cells. Give three examples to support the statement.
Ans:  Tissue-level properties often arise from the organised arrangement and interaction of cells plus extracellular materials. Examples:

(i) Bone: Bone is a specialised connective tissue composed of osteocytes embedded in a mineralised extracellular matrix. The rigid mechanical support and load-bearing function of bone result from the hard, mineralised matrix organised with cells; an individual osteocyte alone cannot provide this mechanical strength.

(ii) Skin surface (dry and protective): The water-resistant, protective outer surface of skin is produced by multiple layers of keratinised epithelial cells and their secretions. This protective property is emergent from layered organisation and keratin deposition, not a property of a single epithelial cell.

(iii) Blood (transport): Blood as a tissue transports gases, nutrients and wastes because of the combined actions of plasma (the fluid matrix) and formed elements (red blood cells, white blood cells and platelets). Individual blood cells cannot perform the full transport and regulatory functions that the whole blood performs as an integrated tissue.

These examples show that tissue functions depend on the collective structure and interactions among cells and extracellular components rather than on isolated cells alone.