The Living World

Chapter 1: The Living World from the NCERT Biology textbook for Class 11 introduces the fundamental concepts of life and its diversity. It delves into the characteristics that distinguish living organisms from non-living objects and explores the vast array of life forms on Earth.

Key Concepts:

Characteristics of Living Organisms: The chapter outlines the essential features that define life, including:
- Growth: An increase in size and mass due to cell division.
- Reproduction: The ability to produce offspring.
- Nutrition: The intake of food and its conversion into energy.
- Excretion: The removal of waste products from the body.
Biodiversity: The chapter explores the incredible variety of life on Earth, highlighting the diversity of species, ecosystems, and genetic variation.
Classification: It introduces the concept of classification, a system used to group organisms based on shared characteristics. The chapter discusses the taxonomic hierarchy, including kingdoms, phyla, classes, orders, families, genera, and species.
Nomenclature: The chapter explains binomial nomenclature, a system of naming organisms using a two-word Latin name, consisting of the genus and species.
Taxonomic Categories: It outlines the different taxonomic categories and their importance in understanding relationships between organisms.

In essence, “The Living World” provides a foundational understanding of the characteristics of life, its diversity, and the classification systems used to organize it. It lays the groundwork for further exploration of biological concepts in subsequent chapters.

Exercise

1.Why are living organisms classified?

Ans :

Organize and understand the vast diversity of life: With millions of species on Earth, classification helps to group organisms based on shared characteristics, making it easier to study and understand them.

Identify and name organisms: Classification provides a standardized system for naming organisms, ensuring that scientists worldwide can communicate and understand each other.

Understand evolutionary relationships: By studying the relationships between different groups of organisms, scientists can trace their evolutionary history and understand how they have evolved over time.

Predict the characteristics of organisms: Based on the classification of an organism, scientists can make educated guesses about its characteristics, such as its habitat, diet, and behavior.

Manage and conserve biodiversity: Classification helps in identifying and protecting endangered species and ecosystems, as well as in managing natural resources effectively.

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

Ans :

New discoveries: As scientists continue to explore and study new species, they may find that existing classifications need to be revised or expanded to accommodate these new findings.

Advances in technology: Technological advancements, such as DNA sequencing and molecular analysis, provide new insights into the genetic relationships between organisms, leading to changes in classification.

Changing understanding of evolutionary relationships: Our understanding of evolutionary relationships between organisms is constantly evolving as new evidence is gathered. This can lead to changes in classification as we refine our understanding of how different groups of organisms are related.

International collaboration: Classification systems are often developed through international collaboration, involving scientists from various countries. As new information and perspectives are shared, classification systems may be updated to reflect these global contributions.

Need for consistency: Classification systems need to be consistent and widely accepted in order to facilitate scientific communication and research. As new information becomes available, classification systems may be revised to ensure that they remain up-to-date and relevant.

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

Ans :

1. Shared Interests

2. Personality Traits

3. Values

4. Social Connections

5. Geographic Location

6. Demographic Factors

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

Ans : The identification of individuals and populations provides a wealth of information that can be used to address a wide range of scientific, environmental, and societal challenges.

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

Mangifera Indica Mangifera indica

Ans : Mangifera indica is the correctly written scientific name of mango.

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

Ans :

A taxon (plural: taxa) is a taxonomic unit, or a group of organisms that share a common ancestor. It can refer to any level of the taxonomic hierarchy, from a kingdom to a species.

Here are some examples of taxa at different hierarchical levels:

Kingdom: Animalia (animals), Plantae (plants), Fungi (fungi), Bacteria (bacteria), Archaea (archaea)

Phylum: Chordata (animals with a notochord), Arthropoda (insects, spiders, crustaceans), Angiospermae (flowering plants)

Class: Mammalia (mammals), Aves (birds), Reptilia (reptiles), Insecta (insects)

Order: Carnivora (carnivores), Primates (primates), Rosales (roses)

Family: Felidae (cats), Hominidae (humans and apes), Rosaceae (roses)

Genus: Panthera (tigers, lions, leopards), Homo (humans), Rosa (roses)

Species: Panthera tigris (tiger), Homo sapiens (human), Rosa indica (rose)

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

(a) Species —> Order —> Phylum —> Kingdom

(b) Genus—) Species—> OrderKingdom

(c) Species —> Genus —>Order —> Phylu

Ans :

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.

Ans :

The concept of “species” has been debated and defined in various ways throughout history.

In the case of higher plants and animals:

The biological species concept is often used, as reproductive isolation is relatively easy to observe and study.
However, there are exceptions, such as ring species, where populations can interbreed with adjacent populations but not with those at the opposite end of the ring.

In the case of bacteria:

The biological species concept is less applicable due to the asexual reproduction of bacteria.
The phylogenetic species concept is often used, focusing on the genetic differences between bacterial strains.
However, even this concept can be challenging due to the rapid evolution and horizontal gene transfer that occur in bacteria.

9. Define and understand the following terms:

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

Ans :

(i) Phylum

Definition: A major taxonomic category below kingdom. It groups organisms with similar body plans and developmental patterns.
Example: Chordata (animals with a notochord), Arthropoda (insects, spiders, crustaceans)

(ii) Class

Definition: A taxonomic category below phylum. It groups organisms within a phylum that share more specific characteristics.
Example: Mammalia (mammals), Aves (birds), Reptilia (reptiles)

(iii) Family

Definition: A taxonomic category below class. It groups organisms within a class that have similar anatomical features and evolutionary relationships.
Example: Felidae (cats), Hominidae (humans and apes), Rosaceae (roses)

(iv) Order

Definition: A taxonomic category below family. It groups organisms within a family that share more specific characteristics and evolutionary relationships.
Example: Carnivora (carnivores), Primates (primates), Rosales (roses)

(v) Genus

Definition: A taxonomic category below order. It groups closely related organisms that share a common ancestor and have similar characteristics.
Example: Panthera (tigers, lions, leopards), Homo (humans), Rosa (roses)

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

Ans :

Plant Example: Mango (Mangifera indica)