Chapter 1 : The Living World

Class 11 Biology Chapter 1. The Living World Exercise Questions and Answers

1. Why are living organisms classified?

Answer : Living organisms are classified to organize and understand the diversity of life on Earth. Classification helps scientists group similar organisms based on their characteristics and evolutionary relationships. This makes it easier to study and communicate about different species, ensuring that we can identify, name, and learn about the millions of species that exist in our world.

2. Why are the classification systems changing every now and then?

Answer : Classification systems change because our understanding of organisms evolves with new scientific discoveries. Advances in genetics and technology reveal more about how species are related, leading to updates in classifications. Additionally, as more species are discovered, they may not fit neatly into existing categories. So, classification systems adapt to reflect the most accurate and up-to-date information about the diversity of life on Earth.

3. What different criteria would you choose to classify people that you meet often?

Answer :  The criteria for classifying people we meet often can vary based on personal, social, and contextual factors, and are not strictly based on the principles of biological classification.

Some common criteria might are :

Gender: Male, female, non-binary, etc.

Skin Color: Based on varying melanin levels.

Height: Tall, average, short, etc.

Hobbies and Interests: Shared activities or passions.

Personality Traits: Nature (introverted, extroverted), values, and attitudes.

Age: Children, teenagers, adults, seniors.

Occupation: Professional roles or job titles.

Cultural Background: Ethnicity, nationality, language.

Relationship: Family, friends, colleagues, acquaintances.

Location: Local, long-distance, neighborhood.

4. What do we learn from identification of individuals and populations?

Answer : The identification of individuals and populations, through standardized nomenclature, ensures clarity and consistency in communication about living organisms worldwide. It facilitates accurate taxonomy, biodiversity conservation, and the exchange of scientific knowledge, reducing confusion and enabling effective research and conservation efforts.

5. Given below is the scientific name of Mango. Identify the correctly written name.

Mangifera Indica

Mangifera indica

Answer : The correctly written scientific name for Mango is "Mangifera indica." In scientific nomenclature, the genus name (Mangifera) should be capitalized, and the species name (indica) should be in lowercase.

6. Define a taxon. Give some examples of taxa at different hierarchical levels.

Answer :  A taxon is a unit of classification in the hierarchical structure of taxonomy.

Examples of taxa at different hierarchical levels are:

(a) Kingdom (e.g., Animalia, Plantae)

(b) Phylum (e.g., Chordata, Arthropoda)

(c) Class (e.g., Mammalia, Insecta)

(d) Order (e.g., Carnivora, Coleoptera)

(e) Family (e.g., Felidae, Rosaceae)

(f) Genus (e.g., Panthera, Rosa)

(g) Species (e.g., Panthera leo, Rosa canina)

Each taxon represents a specific rank within the taxonomic hierarchy and is used to classify organisms based on their shared characteristics.

7. Can you identify the correct sequence of taxonomical categories?

(a) Species → Order → Phylum → Kingdom

(b) Genus → Species → Order → Kingdom

(c) Species → Genus → Order → Phylum

Answer : The correct sequences of taxonomical categories are:

(a) Species → Order → Phylum → Kingdom

(c) Species → Genus → Order → Phylum

8. Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand, and bacteria on the other hand.

Answer : The term "species" has multiple accepted meanings in biology, and the definition can vary depending on the group of organisms being considered. Here are the primary meanings:

Biological Species Concept : This concept, often applied to higher plants and animals, defines a species as a group of interbreeding or potentially interbreeding populations that are reproductively isolated from other such groups. In simpler terms, if individuals can mate and produce fertile offspring, they are considered the same species.

Morphological Species Concept : Species are identified based on physical characteristics and similarities in appearance. This concept is used when reproductive information is limited or unavailable.

Phylogenetic Species Concept : Species are categorized based on their evolutionary history and genetic relatedness. This approach relies heavily on genetic data, such as DNA sequencing.

For higher plants and animals, the Biological Species Concept is commonly applied, focusing on reproductive compatibility. However, for bacteria, which reproduce asexually and have substantial genetic diversity, species definitions include genetic relatedness, phenotypic traits, and ecological niches. Bacterial taxonomy is complex and evolving due to advancements in DNA sequencing and our growing understanding of microbial diversity. Discussing these differences with a teacher can provide a deeper understanding of the various interpretations and applications of the term "species" in biology.

9. Define and understand the following terms:

(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus

Answer :  (i) Phylum : Phylum is a taxonomic rank in the biological classification system. It represents a higher-level category that includes classes of animals such as fishes, amphibians, reptiles, birds, and mammals. These classes share common characteristics, such as the presence of a notochord and a dorsal hollow neural system, and are grouped together within the phylum Chordata. In the context of plants, classes that share a few similar characteristics are assigned to a higher taxonomic category called Division.

(ii) Class : Class is a taxonomic rank that represents a category within the biological classification system. It includes related orders of organisms. For instance, in the class Mammalia, there are various orders like Primata, which consists of monkeys, gorillas, and gibbons, and Carnivora, which includes animals like tigers, cats, and dogs. Class Mammalia encompasses a variety of other orders with shared characteristics.

(iii) Family : Order is a taxonomic rank within the biological classification system. It represents a higher-level category that groups together related families. Orders are identified based on an aggregation of shared characteristics. While the number of similarities is fewer than those within a family, they are still significant. For instance, in the animal kingdom, the order Carnivora includes families like Felidae and Canidae, which encompass a range of species with both shared and differing features.

(iv) Order : Order  is a taxonomic rank in the biological classification system. It represents a higher-level category in which families with a few shared characteristics are grouped together. Orders are identified based on aggregates of characters, and while the number of shared characters is fewer than those found within a family, they are still significant. For example, the plant order Polymoniales includes families like Convolvulaceae and Solanaceae, mainly based on shared floral characters. In the animal kingdom, the order Carnivora includes families like Felidae and Canidae.

(v) Genus :  Genus is a taxonomic rank comprising a group of closely related species that share a higher number of common characteristics in comparison to species from different genera. It is a level in the classification system that helps organize and differentiate species based on their shared traits and evolutionary relationships within a broader category. For example, potato and brinjal are two different species but both belong to the genus Solanum.

10. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

Answer : The taxonomical hierarchy with examples of a plant (Mango) and an animal (Man) are :

This table illustrates the taxonomical hierarchy for a Mango plant and a Human (Man), highlighting how they are categorized from the highest level of Kingdom down to the lowest level of Species based on their shared characteristics and evolutionary relationships.