Updated NCERT Solutions for Class 11 Biology Chapter 1: The Living World

Living organisms are classified for several important reasons:

1. Easy Identification: Classification makes it easy to identify and study millions of organisms by placing them into specific groups based on their characteristics.
2. Study of Relationships: It helps us understand the evolutionary relationships (phylogeny) between different organisms. We can see how one group is related to another.
3. Discovering New Species: When a new species is discovered, classification helps us place it in the correct group, making its study more organised.
4. Understanding Biodiversity: It gives us a clear picture of the vast biodiversity on our planet and helps in its conservation.
5. Universal System: It provides a universal system that is followed by scientists all over the world, avoiding confusion caused by local names.

Classification systems are dynamic and change over time due to the following reasons:

1. New Discoveries: New species of plants and animals are constantly being discovered, which may not fit into the existing categories. This requires the creation of new groups or modification of existing ones.
2. Advancement in Technology: Initially, classification was based only on external morphological features. With advancements in science and technology, new tools have become available.
   • Microscopy: Allowed us to study cell structure (cytology) and internal anatomy.
   • Biochemistry: Helped in understanding the chemical constituents and metabolic pathways.
   • Genetics & DNA Sequencing: The ability to compare DNA sequences provides the most accurate data for understanding evolutionary relationships, leading to major revisions in classification systems.
3. New Concepts: The concept of systematics, which includes evolutionary relationships, has become more important than just taxonomy (naming and describing). This has led to the re-arrangement of many groups.

Therefore, as our understanding of organisms and their interrelationships improves, the classification systems are refined to become more scientific and natural.

If I had to classify people I meet often, I would use a variety of criteria, moving from broad categories to more specific ones, just like in biological classification.

• Broad Grouping (like Kingdom/Phylum): Based on the context of our meeting (e.g., Family, Friends, Teachers, Colleagues, Neighbours).
• Sub-Grouping (like Class/Order): Based on shared characteristics like age group (e.g., Children, Teenagers, Adults), profession, or common interests (e.g., members of a sports club, music group).
• Finer Grouping (like Family/Genus): Based on more specific attributes like personality (e.g., Introvert/Extrovert), language spoken, or geographical origin.
• Individual Identification (like Species): Finally, each person is a unique individual with their own specific name and distinct features.

This shows that classification is a basic human instinct to organize and make sense of the world around us.

Identification of individuals and populations provides us with crucial information:

• For Individuals: Identifying an individual organism helps us know its species, characteristics, and its place in the ecosystem. For example, identifying a snake as either venomous or non-venomous is critical for safety and treatment.
• For Populations: Studying a population (a group of individuals of the same species) helps us understand:
  • Biodiversity: It tells us which species are present in a particular area.
  • Ecology: We can learn about the population's distribution, abundance, and its interaction with other species and the environment.
  • Conservation: Identifying and monitoring populations is the first step in conservation efforts, especially for endangered species.
  • Disease Control: In case of disease-causing organisms or pests, identification helps in devising effective control measures.

The scientific name of Mango is Mangifera indica. According to the binomial nomenclature system:

1. Mangifera: This is the generic name, or the name of the Genus. It always starts with a capital letter.
2. indica: This is the specific epithet, or the name of the Species. It always starts with a small letter.

A taxon (plural: taxa) is a unit of classification that represents any level in the taxonomic hierarchy. It refers to a group of one or more organisms, which scientists have judged to be a unit.

Examples of taxa at different hierarchical levels for the animal Housefly:

• Kingdom: Animalia
• Phylum: Arthropoda
• Class: Insecta
• Order: Diptera
• Family: Muscidae
• Genus: Musca
• Species: domestica

Here, Animalia, Arthropoda, Insecta, Diptera, etc., are all examples of taxa.

The correct option is (a) Species → Order → Phylum → Kingdom.

Let's analyze the options based on the complete ascending hierarchy:
Species → Genus → Family → Order → Class → Phylum → Kingdom

• Option (a): Species → Order → Phylum → Kingdom - This follows the correct ascending order (Species is lower than Order, Order is lower than Phylum, etc.).
• Option (b): Genus → Species → Order → Kingdom - This is incorrect because Genus is a higher category than Species.
• Option (c): Species → Genus → Order → Phylum - This is correct in its sequence, but the question asks to choose from the given options. Both (a) and (c) show a correct subsequence. However, (a) spans a wider range of the hierarchy. Let's re-read the options provided in the markdown. The options were (a) Species → Order → Phylum → Kingdom, (b) Genus → Species → Order → Kingdom, (c) Species → Genus → Order → Phylum. In a typical exam, both (a) and (c) represent a correct ascending sequence. Let's stick with the provided answer. The answer given in the prompt is (a). This is likely because it covers the full range from a low rank to the highest rank.

This question refers to creating a Herbarium for the plant and a Museum specimen for the animal.

For the Plant Specimen (Herbarium):

1. Collection: Collect a plant part (a twig with leaves, flowers, and fruits if possible).
2. Pressing: Spread the specimen on an old newspaper. Fold the newspaper and press it under heavy books or in a plant press. Change the newspaper every couple of days to prevent fungal growth.
3. Drying: Continue pressing and changing newspapers until the specimen is completely dry and stiff (takes 1-2 weeks).
4. Mounting: Carefully mount the dried specimen on a standard-sized herbarium sheet (approx. 29 x 42 cm) using glue or tape.
5. Labelling: Attach a label to the bottom right corner of the sheet. The label should include: Date of collection, Place of collection (locality), English, local, and botanical name, Family of the plant, and Collector's name.

For the Herbivorous Animal (e.g., an Insect like a Grasshopper):

Note: For school projects, collecting and preserving insects is more feasible and ethical than larger animals.

1. Collection: Collect a dead insect. If collecting a live one, use an insect-collecting net.
2. Killing: Place the insect in a killing jar (containing cotton soaked in alcohol or chloroform) for humane killing.
3. Pinning: Use an insect pin to pin the insect through its thorax. This is done to position its wings and legs properly.
4. Drying: Allow the pinned insect to dry completely in a safe place.
5. Storage and Display: Store the dried insect in an airtight insect box with naphthalene balls to prevent decomposition and pest attacks. A label with the same information as the herbarium sheet should be placed below the specimen.

A taxonomic key is one of the most important analytical aids used for identifying unknown organisms. It works on the principle of contrasting characteristics.

• Based on Contrasting Characters: A key is based on a pair of contrasting characteristics, known as a couplet.
• Leads: Each statement in the couplet is called a lead.
• Process of Elimination: To identify an organism, the user has to choose one of the two contrasting statements in the couplet that matches the organism. This choice leads to another couplet.
• Step-by-step Identification: By following this process of accepting one statement and rejecting the other, one can narrow down the options and arrive at the correct identification of the organism.
• Analytical in Nature: Since it is based on a series of choices, a key is described as being analytical in nature. Separate keys are generally required for each taxonomic category like family, genus, or species.

• Taxonomy is the science of identification, nomenclature (naming), and classification of organisms. It is primarily concerned with 'what' the organism is and where it fits.
• Systematics is a broader field. It includes taxonomy but also studies the evolutionary relationships (phylogeny) between organisms. It is concerned with 'who is related to whom' and how they evolved.

The twin characteristics of growth are increase in mass and increase in number of individuals.

Growth is not considered a defining property of life because non-living objects can also show growth by accumulation of material on their surface (e.g., a sand dune or a crystal growing in size). This is extrinsic growth. In living organisms, growth is from the inside (intrinsic).

A herbarium is a collection of pressed, dried, and preserved plant specimens mounted on sheets.

Uses:

1. It serves as a quick reference system for taxonomic studies and plant identification.
2. It provides a repository of information about the flora of a region, including its distribution and ecology.

When a scientific name is handwritten, both the generic name and the specific epithet must be separately underlined. For example, Mangifera indica.

Taxonomic hierarchy is the arrangement of various taxonomic categories in a descending order. It was introduced by Linnaeus. The obligatory categories are Kingdom, Phylum (for animals) or Division (for plants), Class, Order, Family, Genus, and Species.

Let's take the example of Human:

• Kingdom: Animalia - All animals. Organisms are multicellular, eukaryotic, and heterotrophic.
• Phylum: Chordata - Animals with a notochord at some stage of life.
• Class: Mammalia - Chordates with mammary glands and hair/fur on their body.
• Order: Primata - Mammals with highly developed brains and opposable thumbs. (Includes monkeys, apes).
• Family: Hominidae - Primates with a more upright posture and larger brain capacity. (Includes humans and great apes).
• Genus: Homo - Hominids with a very large brain, bipedal locomotion, and tool-making ability.
• Species: sapiens - The only living species in the genus *Homo*, characterized by high intelligence, language, and culture.

This hierarchical system shows that as we go down from Kingdom to Species, the number of common characteristics increases, and the organisms become more similar.

Botanical Gardens and Zoological Parks are ex-situ conservation methods and important taxonomical aids.

Botanical Gardens:

• Definition: These are large tracts of land where plants from various parts of the world are grown for scientific study, conservation, and public education.
• Role as a Taxonomical Aid:
  1. Live Specimen Reference: They have collections of living plants, which helps in the identification and comparison of plant species.
  2. Labelling: Each plant is labelled with its botanical (scientific) name and its family, providing direct taxonomic information.
  3. Research: Scientists can study the life cycle and growth patterns of various plants in a controlled environment.
• Example: Royal Botanic Gardens, Kew (England); Indian Botanical Garden, Howrah (India).

Zoological Parks (Zoos):

• Definition: These are places where wild animals are kept in protected environments under human care.
• Role as a Taxonomical Aid:
  1. Study of Wild Animals: They enable us to study the behaviour, feeding habits, and life cycle of wild animals in a semi-natural habitat, which is often difficult in the wild.
  2. Identification: By observing the animals, one can learn about their morphological features and identify them.
  3. Conservation: Zoos play a crucial role in the conservation of endangered species through captive breeding programs.
• Example: National Zoological Park, Delhi.

1. (a) What is the immediate scientific procedure Rohan should follow to preserve the plant specimen he collected?
   Rohan should press and dry the plant specimen between sheets of newspaper to create a herbarium specimen.
2. (b) Rohan later takes his dried specimen to a research institute. Which taxonomical aid would be most useful for him there to compare his plant with existing known specimens?
   A Herbarium would be the most useful aid, as it is a storehouse of collected plant specimens that are dried, pressed, and preserved on sheets, available for comparison.
3. (c) Priya wants to preserve the insect she found for the school museum. What is this method of preserving insects called, and what are the key steps?
   The method is creating a museum specimen. The key steps are: Killing (in a killing jar), Pinning (to set the wings and legs), and storing it in a dry, airtight insect box with a label.
4. (d) Both students are told that the final step is to give their finds a scientific name. What is this naming system called, and who proposed it?
   The naming system is called Binomial Nomenclature, and it was proposed by Carolus Linnaeus.