NCERT Class 11 Biology Chapter 1 Notes - The Living World PDF Notes

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This chapter explains the diversity of life and how living organisms are identified and classified. Students can download the PDF of NCERT Class 11 Biology Chapter 1 Notes. This PDF can be used offline to study anytime and anywhere. The NCERT Notes for Class 11 Biology are a valuable resource to score well in exams.

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NCERT Class 11 Biology Chapter 1 Notes

These notes help students understand Chapter 1 simply and clearly. They cover what makes something living, how living things are grouped, and the basics of scientific naming. The Living World Class 11 Notes include short, easy-to-learn points so students can follow and remember the topics better.

What is Living?

“Living” means those organisms that show some special features that nonliving things can’t.

• The main things to know are growth, reproduction, metabolism, and response to changes around them.

• Growth is when the size and number of cells increase, which happens in both one-celled and multicelled both.

• Reproduction helps to keep the species continuity, and can be sexual or asexual.

• Sexual type brings variation, asexual reproduction only increases the number.

• Metabolism is basically all the chemical reactions happening to keep life going.

• Responding to surroundings is something only living beings can do.

• These things are not because of one molecule, but how many molecules work together in cells.

• So overall, you can say a living thing is a system that can evolve and respond to outside changes.

Diversity in the Living World

The word biodiversity was first used by W. Rosen. Life on Earth is incredibly diverse, with millions of species inhabiting it.

• Biodiversity refers to the vast variety of living organisms, including plants, animals, and microorganisms.

• Scientists estimate that over 1.7 million species have been identified, but many more remain undiscovered.

• This diversity is the result of evolution, which allows organisms to adapt to different environmental conditions.

• The study of diversity is important for conservation efforts and understanding the ecological balance.

• By classifying the organisms, biologists organise and study them systematically, making it easier to analyse their characteristics, evolutionary history, and ecological roles.

Binomial Nomenclature

Binomial nomenclature is the scientific system of naming organisms using two Latinized names introduced by Carl Linnaeus.

• The first part represents the genus, and the second part denotes the species. For example, humans are scientifically called Homo sapiens, whereas homo is the genus and sapiens is the species.

• This system provides a universal naming convention, avoiding confusion caused by local or common names.

• The Binomial Nomenclature is governed by international codes such as the International Code of Botanical Nomenclature (ICBN) and the International Code of Zoological Nomenclature (ICZN), ensuring consistency and standardisation in naming living organisms.

Taxonomic Categories

Taxonomic categories refer to the hierarchical system of classification used to organise and categorise living organisms based on their characteristics.

• The classification system follows a structured sequence, with each category representing a specific rank.

• The system was formalised by Carolus Linnaeus and is universally accepted for the classification of organisms.

• The taxonomic hierarchy consists of seven major categories arranged from the broadest to the most specific:

Kingdom

The kingdom is the highest and most inclusive tax economic category.

• It groups organisms with the most fundamental similarities. Initially, Linneaus classified all living organisms into two kingdoms: Plantae, which included plants, and Animalia, which included animals.

• However, with advancements in microbiology and evolutionary studies, the classification expanded to a five-kingdom system proposed by R.H. Whittaker in 1969.

• The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.

• In modern taxonomy, a six-kingdom system is also used, where Monera is divided into Archaebacteria and Bacteria due to significant genetic differences.

Division or Phylum

Phylum (in animals) or Division (in plants) is the next level of classification in which organisms are grouped based on major structural and functional similarities.

• Organisms within a phylum share broad characteristics but may have distinct differences at lower levels.

• Example: Phylum Chordata, which includes vertebrates like fish, amphibians, reptiles, birds, and mammals.

• Division Angiosperms includes flowering plants in the Plant Kingdom.

Class

The class is a more specific taxonomic rank than Phylum or Division.

• It groups organisms within a phylum that share additional similarities. For instance, in the phylum Chordata, organisms are further divided into different classes, such as:

• Class Mammalia includes mammals like humans, cats, and elephants.

• Class Aves, which includes birds like eagles and parrots. Class Reptilia includes reptiles like snakes.

Order

The order is a taxonomic category that groups related families together.

• It reflects more precise similarities between organisms.

• For example, within the class Mammalia, Order Carnivora includes families like Felidae and Canidae, and Order Primata includes families such as Hominidae, which includes great apes and humans.

Family

A family consists of related genera that share a significant number of characteristics.

• It is a more specific level of classification than order.

• Organisms in the same family have many structural and genetic similarities.

• Example: Family Felidae includes genera like Panthera and Felis (cats). Family Canidae includes genera like Canis (dogs)

Genus

The genus is one of the most crucial taxonomic categories.

• It consists of closely related species that share common characteristics but may differ in minor ways.

• The genus name is always written in italics with the first letter capitalised.

• Examples are Homo (including Homo sapiens- humans)

Species

Species is the most specific fundamental taxonomic category.

• Organisms belonging to the same species can interbreed and produce fertile offspring.

• It represents a distinct biological identity.

• For example, Homo sapiens (humans), Felis catus (domestic cats), Panthera tigris (tigers)

Also, Read

• NCERT Notes for Class 11 Physics
• NCERT Notes for Class 11 Chemistry
• NCERT Notes for Class 11 Mathematics

Living World Previous Year Questions and Answers

Some of the questions that have come in past years from the chapter are given below. Referring to the Living World Class 11 Notes, students can understand the features of living organisms.

Question 1. Which of the following is a defining characteristic of living organisms?

Option 1. Growth

Option 2. Ability to make sound

Option 3. Reproduction

Option 4. Response to external stimuli

Answer :

The other characteristic than the response to the stimuli, might not be apparent for any time, but the response to the stimuli could be confirmed whenever required and thus can be considered as the defining characteristic of living organisms.

Hence, the answer is option (4), Response to external stimuli

Question 2. All living organisms are linked to one another because

Option 1. They have common genetic material of the same type

Option 2. They share common genetic material, but to varying degrees

Option 3. All have a common cellular organisation

Option 4. All of the above

Answer :

The theory of evolution proposes that all organisms have a common origin, and this is evident in their genetic material. Over time, variations in this genetic material attributed to mutation, natural selection, and many other evolutionary processes have resulted in the vast diversity of life we see today. Shared genetic heritage establishes the interconnection of all living organisms, showing how gradual evolutionary changes result in the appearance of new species with the retention of genetic properties.

Hence, the correct answer is Option 2. They share common genetic material, but to varying degrees

Question 3. Genus represents

Option 1. An individual plant or animal

Option 2. A collection of plants and animals

Option 3. Group of closely related species of plants and animals

Option 4. None of these

Answer :

Consider that the taxon species comes under the taxon genus. A genus is an aggregate of related species that are similar to each other in many correlated characteristics. The genus can be monotypic, i.e., having one species or polytypic, i.e., having many species. Genus Solanum possesses species like Solanum nigrum, Solanum tuberosum (potato), Solanum melongena (brinjal), etc.

Hence, the answer is option (3) Group of closely related species of plants and animals.

Also Read:

• NCERT Solution
• NCERT Solutions for Class 11
• NCERT Solutions for Class 11 Biology

Chapter-Wise NCERT Class 11 Notes Biology

The chapter-wise Notes for class 11 biology are given below: