CBSE Class 11 Biology Chapter 3: The Living World - NCERT Solutions

Living organisms are classified for several key reasons. Firstly, the Earth hosts an immense diversity of life, with millions of different species varying in size, shape, habitat, and characteristics. Studying each organism individually would be practically impossible. Classification provides a systematic framework to organize this vast biodiversity.

Secondly, classification helps in identifying similarities and dissimilarities among organisms, which is fundamental to understanding their relationships. By grouping organisms based on shared traits and evolutionary history, scientists can make the study of life more manageable and coherent.

Finally, classification systems facilitate the identification, naming (nomenclature), and arrangement of organisms into meaningful groups (taxa), making biological knowledge more accessible and organized.

Classification systems are dynamic and undergo changes primarily because scientific knowledge is constantly expanding. New species are continuously being discovered around the world, and these new organisms need to be incorporated into the existing classification framework.

Furthermore, advancements in scientific understanding, particularly in areas like genetics, molecular biology, and evolutionary studies, provide new insights into the relationships between organisms. These insights may reveal that existing classifications do not accurately reflect evolutionary history, necessitating revisions or the development of entirely new systems.

Therefore, classification systems are updated periodically to reflect the latest discoveries and a more accurate understanding of life's diversity and evolutionary pathways.

To classify people whom I meet often, I could use a hierarchical approach based on various criteria:

1. Initial Broad Classification: Based on gender (e.g., Male, Female). This divides the group into two large categories.
2. Further Classification by Name: Within each gender group, I could classify individuals based on their first names. However, since multiple people might share the same first name, this needs refinement.
3. Classification by Surname: A more refined classification would be based on surnames. This would group individuals who are likely related or share a common lineage.
4. Specific Identification: If surnames are also common, the final level of classification would be based on unique identifiers like roll numbers (in a school context) or specific roles/relationships (e.g., 'my neighbor', 'my classmate', 'my cousin').

This multi-level approach, starting from broad categories and moving to more specific ones, mirrors the principles used in biological classification.

The process of identification involves carefully observing and noting down the characteristics of an individual organism or a population. From this detailed observation, we learn to recognize the similarities and differences that exist among individuals within the same species, and also between different species or groups of organisms.

This knowledge of characteristics is fundamental. It allows scientists to accurately place an organism within a taxonomic framework, enabling them to assign a scientific name and group it with related organisms. Essentially, identification provides the raw data necessary for classification.

The correctly written scientific name of Mango is Mangifera indica.

According to the rules of binomial nomenclature, the scientific name of a species consists of two parts: the genus name and the specific epithet. The genus name must always begin with a capital letter, while the specific epithet must begin with a lowercase letter. Therefore, 'Mangifera' (genus) starts with a capital 'M', and 'indica' (specific epithet) starts with a lowercase 'i'.

A taxon (plural: taxa) refers to any unit or group of organisms that is recognized at any particular level within the hierarchical system of biological classification. Each taxon represents a rank or a step in this hierarchy.

Examples of taxa at different hierarchical levels, in ascending order, are:

• Species: The most basic unit of classification (e.g., sapiens).
• Genus: A group of closely related species (e.g., Homo).
• Family: A group of related genera (e.g., Hominidae).
• Order: A group of related families (e.g., Primates).
• Class: A group of related orders (e.g., Mammalia).
• Phylum: A group of related classes (e.g., Chordata).
• Kingdom: The highest taxonomic rank (e.g., Animalia).

The universally accepted hierarchical arrangement of taxonomic categories in ascending order is:

Species → Genus → Family → Order → Class → Phylum → Kingdom

Let's evaluate the given options based on this hierarchy:

• Option 1: Species → Order → Phylum → Kingdom - This sequence is incorrect because 'Order' should come after 'Family' and before 'Class', and 'Phylum' should come after 'Class'.
• Option 2: Genus → Species → Order → Kingdom - This sequence is incorrect because 'Species' should precede 'Genus' in the ascending order.
• Option 3: Species → Genus → Order → Phylum - This sequence correctly starts with 'Species' followed by 'Genus'. However, it omits 'Family' and 'Class' between 'Genus' and 'Order', and between 'Order' and 'Phylum' respectively. If we consider only the elements present and their relative order, it shows a correct progression from lower to higher ranks, but it is incomplete.

Considering the options provided, none perfectly match the complete hierarchy. However, if we interpret the question as asking for sequences where the relative order of the listed categories is correct, then Option 3 shows a correct progression from Species to Genus, and then to higher ranks like Order and Phylum, even though intermediate ranks are missing. Option 1 and 2 have fundamental order errors (e.g., Genus after Species, Order before Phylum).

Therefore, based on the relative order of the categories presented, Option 3 is the most plausible correct sequence among the choices, despite its incompleteness.