CBSE Class 11 Biology Chapter 1: The Living World NCERT Solutions

Living organisms are classified for several crucial reasons. Earth hosts an immense variety of life forms, including millions of plants, animals, and microorganisms, each differing in size, shape, colour, habitat, and numerous other characteristics. Studying each organism individually would be practically impossible due to this vast diversity.

Classification provides a systematic framework based on established rules and principles. This framework allows scientists to:

• Identify organisms based on their features.
• Assign a universally accepted scientific name (nomenclature).
• Group similar organisms together into categories (classification).

For instance, once an organism is identified as an insect, it can be given a scientific name and placed within the correct group of insects, alongside other similar organisms. This systematic grouping, known as taxonomy, helps in understanding the evolutionary relationships and similarities among different life forms. Ultimately, biological classification makes the study of organisms organized, manageable, and insightful.

Classification systems are dynamic and evolve over time primarily because new species of plants, animals, and microorganisms are continuously being discovered around the world. As scientists identify and describe these new organisms, existing classification systems need to be updated or revised to incorporate them accurately.

Furthermore, advancements in scientific knowledge, particularly in areas like genetics, molecular biology, and evolutionary studies, provide new insights into the relationships between different organisms. These insights often lead to a re-evaluation of existing classifications, prompting changes to better reflect the true evolutionary history and biological connections among life forms.

To classify people whom I meet often, such as classmates, I would use a hierarchical approach based on various criteria:

1. Initial Broad Classification: I could start by classifying them based on gender (e.g., boys and girls). This creates two distinct groups.
2. Further Classification by Name: Within each gender group, I could classify them by their first names. However, since multiple people might share the same first name, this might not be sufficient.
3. Classification by Surname: To refine the classification further, I would use surnames. This would help differentiate individuals who share the same first name.
4. Final Specific Classification: If there are still individuals with the same first and last names (which is rare in a typical class but possible), the final level of classification would be based on their unique roll numbers. This ensures each person is uniquely identified within the group.

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

The process of identifying individuals and studying populations provides valuable information that is fundamental to biological classification. By carefully observing and documenting the characteristics of an individual organism or an entire population, we learn to:

• Recognize the unique features of each organism.
• Identify similarities and differences among individuals within the same species (population).
• Identify similarities and differences between organisms belonging to different species or groups.

This detailed knowledge of characteristics is essential for scientists to accurately place organisms into various taxonomic categories, thereby building the foundation for understanding biodiversity and evolutionary relationships.

The correctly written scientific name of Mango is Mangifera indica.

The rules of binomial nomenclature, a system for naming species, dictate that:

• The scientific name consists of two parts: the genus name and the specific epithet.
• The genus name (e.g., 'Mangifera') must always begin with a capital letter.
• The specific epithet (e.g., 'indica') must always begin with a small letter.
• Both parts, when printed, should be italicized; when handwritten, they should be underlined separately.

Therefore, 'Mangifera indica' follows these conventions correctly, while 'Mangifera Indica' does not, as the specific epithet 'Indica' is incorrectly capitalized.

A taxon (plural: taxa) is defined as any unit or category used in the classification of living organisms. It represents a rank in the hierarchical system of taxonomy. Each taxon includes organisms that share a set of common characteristics defined by that rank.

Examples of taxa at different hierarchical levels, arranged in ascending order from most specific to most general, are:

• Species: The most basic level of classification. Example: indica (referring to a specific type of mango).
• Genus: A group of closely related species. Example: Mangifera (which includes Mangifera indica and other related mango species).
• Family: A group of related genera. Example: Anacardiaceae (the mango family, which includes mangoes, cashews, and pistachios).
• Order: A group of related families. Example: Sapindales (an order that includes families like Anacardiaceae, Sapindaceae, etc.).
• Class: A group of related orders. Example: Magnoliopsida (also known as dicotyledons, which includes many orders like Sapindales).
• Phylum: A group of related classes. Example: Magnoliophyta (the division/phylum for flowering plants).
• Kingdom: The highest level of classification, grouping together all organisms with fundamental similarities. Example: Plantae (the kingdom for all plants).

The standard hierarchical arrangement of taxonomic categories in ascending order is:

Species <math>→</math> Genus <math>→</math> Family <math>→</math> Order <math>→</math> Class <math>→</math> Phylum <math>→</math> Kingdom

Let's evaluate the given sequences:

• Sequence (a): Species → Order → Phylum → Kingdom - This sequence is incorrect because 'Order' comes after 'Genus' and 'Family', not directly after 'Species'. 'Phylum' is also placed incorrectly relative to 'Order'.
• Sequence (b): Genus → Species → Order → Kingdom - This sequence is incorrect because 'Species' is a lower rank than 'Genus' and should precede it in an ascending sequence.
• Sequence (c): Species → Genus → Order → Phylum - This sequence correctly places 'Species' before 'Genus'. However, it omits 'Family', 'Class', and places 'Order' before 'Phylum' without the intermediate ranks. While the initial part (Species → Genus) and the later part (Order → Phylum) are in the correct relative order, the sequence is incomplete and skips intermediate major ranks.

Considering the options provided and the standard hierarchy, none of the sequences are perfectly correct and complete. However, if we interpret the question as asking for sequences that contain correctly ordered adjacent ranks within them, then:

• Sequence (a) has Order → Phylum → Kingdom, which are in correct relative order.
• Sequence (b) has Order → Kingdom, which are in correct relative order.
• Sequence (c) has Species → Genus and Order → Phylum, both of which are correctly ordered adjacent ranks.

Given the typical structure of such questions, it's likely intended that the most complete correct sequence or sequences containing correct adjacent pairs are sought. Sequence (c) starts correctly with Species → Genus. If we assume the question implies partial correct sequences, then both (a) and (c) contain correctly ordered adjacent major ranks. However, the most fundamental correct starting pair is Species → Genus, which is present in (c).

Revisiting the standard hierarchy: Species → Genus → Family → Order → Class → Phylum → Kingdom.

Let's re-evaluate based on the provided options and common textbook representations:

• Option (a) skips Genus, Family, Class.
• Option (b) incorrectly places Genus before Species.
• Option (c) correctly starts with Species → Genus, and then correctly places Order → Phylum. It omits Family and Class.

Therefore, sequence (c) represents the most accurate partial sequence among the choices, correctly ordering the initial and later major ranks. Sequence (a) also contains correctly ordered major ranks (Order → Phylum → Kingdom) but misses the fundamental Species → Genus step.

Final Answer Determination: Based on the standard hierarchy, the sequence Species → Genus is fundamental. Sequence (c) starts with this correct pair. Sequence (a) starts incorrectly by skipping Genus and Family. Sequence (b) reverses Species and Genus. Thus, sequence (c) is the best fit among the given options, despite its incompleteness.