NCERT Textbook: The Living World | Biology Class 11 - NEET PDF Download

 Page 1


Biology is the science of life forms and living processes. The living world
comprises an amazing diversity of living organisms. Early man could
easily perceive the difference between inanimate matter and living
organisms. Early man deified some of the inanimate matter (wind, sea,
fire etc.) and some among the animals and plants. A common feature of
all such forms of inanimate and animate objects was the sense of awe
or fear that they evoked. The description of living organisms including
human beings began much later in human history. Societies which
indulged in anthropocentric view of biology could register limited
progress in biological knowledge. Systematic and monumental
description of life forms brought in, out of necessity, detailed systems
of identification, nomenclature and classification. The biggest spin off
of such studies was the recognition of the sharing of similarities among
living organisms both horizontally and vertically. That all present day
living organisms are related to each other and also to all organisms
that ever lived on this earth, was a revelation which humbled man and
led to cultural movements for conservation of biodiversity. In the
following chapters of this unit, you will get a description, including
classification, of animals and plants from a taxonomist’s perspective.
DIVERSITY IN THE LIVING WORLD
Chapter 1
The Living World
Chapter 2
Biological Classification
Chapter 3
Plant Kingdom
Chapter 4
Animal Kingdom
UNIT 1
2024-25
Page 2


Biology is the science of life forms and living processes. The living world
comprises an amazing diversity of living organisms. Early man could
easily perceive the difference between inanimate matter and living
organisms. Early man deified some of the inanimate matter (wind, sea,
fire etc.) and some among the animals and plants. A common feature of
all such forms of inanimate and animate objects was the sense of awe
or fear that they evoked. The description of living organisms including
human beings began much later in human history. Societies which
indulged in anthropocentric view of biology could register limited
progress in biological knowledge. Systematic and monumental
description of life forms brought in, out of necessity, detailed systems
of identification, nomenclature and classification. The biggest spin off
of such studies was the recognition of the sharing of similarities among
living organisms both horizontally and vertically. That all present day
living organisms are related to each other and also to all organisms
that ever lived on this earth, was a revelation which humbled man and
led to cultural movements for conservation of biodiversity. In the
following chapters of this unit, you will get a description, including
classification, of animals and plants from a taxonomist’s perspective.
DIVERSITY IN THE LIVING WORLD
Chapter 1
The Living World
Chapter 2
Biological Classification
Chapter 3
Plant Kingdom
Chapter 4
Animal Kingdom
UNIT 1
2024-25
Born on 5 July 1904, in Kempten, Germany, ERNST MAYR, the
Harvard University evolutionary biologist who has been called
‘The Darwin of the 20
th
 century’, was one of the 100 greatest
scientists of all time. Mayr joined Harvard’s Faculty of Arts
and Sciences in 1953 and retired in 1975, assuming the title
Alexander Agassiz Professor of Zoology Emeritus. Throughout
his nearly 80-year career, his research spanned ornithology,
taxonomy, zoogeography, evolution, systematics, and the
history and philosophy of biology. He almost single-handedly
made the origin of species diversity the central question of
evolutionary biology that it is today. He also pioneered the
currently accepted definition of a biological species. Mayr was
awarded the three prizes widely regarded as the triple crown of
biology: the Balzan Prize in 1983, the International Prize for
Biology in 1994, and the Crafoord Prize in 1999. Mayr died at
the age of 100 in the year 2004.
Ernst Mayr
(1904 – 2004)
2024-25
Page 3


Biology is the science of life forms and living processes. The living world
comprises an amazing diversity of living organisms. Early man could
easily perceive the difference between inanimate matter and living
organisms. Early man deified some of the inanimate matter (wind, sea,
fire etc.) and some among the animals and plants. A common feature of
all such forms of inanimate and animate objects was the sense of awe
or fear that they evoked. The description of living organisms including
human beings began much later in human history. Societies which
indulged in anthropocentric view of biology could register limited
progress in biological knowledge. Systematic and monumental
description of life forms brought in, out of necessity, detailed systems
of identification, nomenclature and classification. The biggest spin off
of such studies was the recognition of the sharing of similarities among
living organisms both horizontally and vertically. That all present day
living organisms are related to each other and also to all organisms
that ever lived on this earth, was a revelation which humbled man and
led to cultural movements for conservation of biodiversity. In the
following chapters of this unit, you will get a description, including
classification, of animals and plants from a taxonomist’s perspective.
DIVERSITY IN THE LIVING WORLD
Chapter 1
The Living World
Chapter 2
Biological Classification
Chapter 3
Plant Kingdom
Chapter 4
Animal Kingdom
UNIT 1
2024-25
Born on 5 July 1904, in Kempten, Germany, ERNST MAYR, the
Harvard University evolutionary biologist who has been called
‘The Darwin of the 20
th
 century’, was one of the 100 greatest
scientists of all time. Mayr joined Harvard’s Faculty of Arts
and Sciences in 1953 and retired in 1975, assuming the title
Alexander Agassiz Professor of Zoology Emeritus. Throughout
his nearly 80-year career, his research spanned ornithology,
taxonomy, zoogeography, evolution, systematics, and the
history and philosophy of biology. He almost single-handedly
made the origin of species diversity the central question of
evolutionary biology that it is today. He also pioneered the
currently accepted definition of a biological species. Mayr was
awarded the three prizes widely regarded as the triple crown of
biology: the Balzan Prize in 1983, the International Prize for
Biology in 1994, and the Crafoord Prize in 1999. Mayr died at
the age of 100 in the year 2004.
Ernst Mayr
(1904 – 2004)
2024-25
How wonderful is the living world ! The wide range of living types is
amazing. The extraordinary habitats in which we find living organisms,
be it cold mountains, deciduous forests, oceans, fresh water lakes, deserts
or hot springs, leave us speechless. The beauty of a galloping horse, of
the migrating birds, the valley of flowers or the attacking shark evokes
awe and a deep sense of wonder. The ecological conflict and cooperation
among members of a population and among populations of a community
or even the molecular traffic inside a cell make us deeply reflect on – what
indeed is life? This question has two implicit questions within it. The first
is a technical one and seeks answer to what living is as opposed to the
non-living, and the second is a philosophical one, and seeks answer to
what the purpose of life is. As scientists, we shall not attempt answering
the second question. We will try to reflect on – what is living?
1.1 DIVERSITY IN THE LIVING WORLD
If you look around you will see a large variety of living organisms, be it
potted plants, insects, birds, your pets or other animals and plants. There
are also several organisms that you cannot see with your naked eye but
they are all around you. If you were to increase the area that you make
observations in, the range and variety of organisms that you see would
increase. Obviously, if you were to visit a dense forest, you would probably
see a much greater number and kinds of living organisms in it. Each
different kind of plant, animal or organism that you see, represents a
species. The number of species that are known and described range
between 1.7-1.8 million. This refers to biodiversity or the number and
THE LIVING WORLD
CHAPTER  1
1.1 Diversity in the
Living World
1.2 Taxonomic
Categories
2024-25
Page 4


Biology is the science of life forms and living processes. The living world
comprises an amazing diversity of living organisms. Early man could
easily perceive the difference between inanimate matter and living
organisms. Early man deified some of the inanimate matter (wind, sea,
fire etc.) and some among the animals and plants. A common feature of
all such forms of inanimate and animate objects was the sense of awe
or fear that they evoked. The description of living organisms including
human beings began much later in human history. Societies which
indulged in anthropocentric view of biology could register limited
progress in biological knowledge. Systematic and monumental
description of life forms brought in, out of necessity, detailed systems
of identification, nomenclature and classification. The biggest spin off
of such studies was the recognition of the sharing of similarities among
living organisms both horizontally and vertically. That all present day
living organisms are related to each other and also to all organisms
that ever lived on this earth, was a revelation which humbled man and
led to cultural movements for conservation of biodiversity. In the
following chapters of this unit, you will get a description, including
classification, of animals and plants from a taxonomist’s perspective.
DIVERSITY IN THE LIVING WORLD
Chapter 1
The Living World
Chapter 2
Biological Classification
Chapter 3
Plant Kingdom
Chapter 4
Animal Kingdom
UNIT 1
2024-25
Born on 5 July 1904, in Kempten, Germany, ERNST MAYR, the
Harvard University evolutionary biologist who has been called
‘The Darwin of the 20
th
 century’, was one of the 100 greatest
scientists of all time. Mayr joined Harvard’s Faculty of Arts
and Sciences in 1953 and retired in 1975, assuming the title
Alexander Agassiz Professor of Zoology Emeritus. Throughout
his nearly 80-year career, his research spanned ornithology,
taxonomy, zoogeography, evolution, systematics, and the
history and philosophy of biology. He almost single-handedly
made the origin of species diversity the central question of
evolutionary biology that it is today. He also pioneered the
currently accepted definition of a biological species. Mayr was
awarded the three prizes widely regarded as the triple crown of
biology: the Balzan Prize in 1983, the International Prize for
Biology in 1994, and the Crafoord Prize in 1999. Mayr died at
the age of 100 in the year 2004.
Ernst Mayr
(1904 – 2004)
2024-25
How wonderful is the living world ! The wide range of living types is
amazing. The extraordinary habitats in which we find living organisms,
be it cold mountains, deciduous forests, oceans, fresh water lakes, deserts
or hot springs, leave us speechless. The beauty of a galloping horse, of
the migrating birds, the valley of flowers or the attacking shark evokes
awe and a deep sense of wonder. The ecological conflict and cooperation
among members of a population and among populations of a community
or even the molecular traffic inside a cell make us deeply reflect on – what
indeed is life? This question has two implicit questions within it. The first
is a technical one and seeks answer to what living is as opposed to the
non-living, and the second is a philosophical one, and seeks answer to
what the purpose of life is. As scientists, we shall not attempt answering
the second question. We will try to reflect on – what is living?
1.1 DIVERSITY IN THE LIVING WORLD
If you look around you will see a large variety of living organisms, be it
potted plants, insects, birds, your pets or other animals and plants. There
are also several organisms that you cannot see with your naked eye but
they are all around you. If you were to increase the area that you make
observations in, the range and variety of organisms that you see would
increase. Obviously, if you were to visit a dense forest, you would probably
see a much greater number and kinds of living organisms in it. Each
different kind of plant, animal or organism that you see, represents a
species. The number of species that are known and described range
between 1.7-1.8 million. This refers to biodiversity or the number and
THE LIVING WORLD
CHAPTER  1
1.1 Diversity in the
Living World
1.2 Taxonomic
Categories
2024-25
4 BIOLOGY
types of organisms present on earth. We should remember here that as
we explore new areas, and even old ones, new organisms are continuously
being identified.
As stated earlier, there are millions of plants and animals in the world;
we know the plants and animals in our own area by their local names.
These local names would vary from place to place, even within a country.
Probably you would recognise the confusion that would be created if we
did not find ways and means to talk to each other, to refer to organisms
we are talking about.
Hence, there is a need to standardise the naming of living organisms
such that a particular organism is known by the same name all over the
world. This process is called nomenclature. Obviously, nomenclature
or naming is only possible when the organism is described correctly and
we know to what organism the name is attached to. This is identification.
In order to facilitate the study, number of scientists have established
procedures to assign a scientific name to each known organism.  This is
acceptable to biologists all over the world. For plants, scientific names are
based on agreed principles and criteria, which are provided in International
Code for Botanical Nomenclature (ICBN). You may ask, how  are animals
named? Animal taxonomists have evolved International Code of Zoological
Nomenclature (ICZN). The scientific names ensure that each organism
has only one name. Description of any organism should enable the people
(in any part of the world) to arrive at the same name. They also ensure
that such a name has not been used for any other known organism.
Biologists follow universally accepted principles to provide scientific
names to known organisms.  Each name has two components – the
Generic name and the specific epithet. This system of providing a
name with two components is called Binomial nomenclature. This
naming system given by Carolus Linnaeus is being practised by biologists
all over the world. This naming system using a two word format was
found convenient. Let us take the example of mango to understand the
way of providing scientific names better. The scientific name of mango is
written as Mangifera indica. Let us see how it is a binomial name.  In this
name Mangifera represents the genus while indica, is a particular species,
or a specific epithet. Other universal rules of nomenclature are as follows:
1. Biological names are generally in Latin and written in italics.
They are Latinised or derived from Latin irrespective of their
origin.
2. The first word in a biological name represents the genus while
the second component denotes the specific epithet.
3. Both the words in a biological name, when handwritten, are
separately underlined, or printed in italics to indicate their Latin
origin.
2024-25
Page 5


Biology is the science of life forms and living processes. The living world
comprises an amazing diversity of living organisms. Early man could
easily perceive the difference between inanimate matter and living
organisms. Early man deified some of the inanimate matter (wind, sea,
fire etc.) and some among the animals and plants. A common feature of
all such forms of inanimate and animate objects was the sense of awe
or fear that they evoked. The description of living organisms including
human beings began much later in human history. Societies which
indulged in anthropocentric view of biology could register limited
progress in biological knowledge. Systematic and monumental
description of life forms brought in, out of necessity, detailed systems
of identification, nomenclature and classification. The biggest spin off
of such studies was the recognition of the sharing of similarities among
living organisms both horizontally and vertically. That all present day
living organisms are related to each other and also to all organisms
that ever lived on this earth, was a revelation which humbled man and
led to cultural movements for conservation of biodiversity. In the
following chapters of this unit, you will get a description, including
classification, of animals and plants from a taxonomist’s perspective.
DIVERSITY IN THE LIVING WORLD
Chapter 1
The Living World
Chapter 2
Biological Classification
Chapter 3
Plant Kingdom
Chapter 4
Animal Kingdom
UNIT 1
2024-25
Born on 5 July 1904, in Kempten, Germany, ERNST MAYR, the
Harvard University evolutionary biologist who has been called
‘The Darwin of the 20
th
 century’, was one of the 100 greatest
scientists of all time. Mayr joined Harvard’s Faculty of Arts
and Sciences in 1953 and retired in 1975, assuming the title
Alexander Agassiz Professor of Zoology Emeritus. Throughout
his nearly 80-year career, his research spanned ornithology,
taxonomy, zoogeography, evolution, systematics, and the
history and philosophy of biology. He almost single-handedly
made the origin of species diversity the central question of
evolutionary biology that it is today. He also pioneered the
currently accepted definition of a biological species. Mayr was
awarded the three prizes widely regarded as the triple crown of
biology: the Balzan Prize in 1983, the International Prize for
Biology in 1994, and the Crafoord Prize in 1999. Mayr died at
the age of 100 in the year 2004.
Ernst Mayr
(1904 – 2004)
2024-25
How wonderful is the living world ! The wide range of living types is
amazing. The extraordinary habitats in which we find living organisms,
be it cold mountains, deciduous forests, oceans, fresh water lakes, deserts
or hot springs, leave us speechless. The beauty of a galloping horse, of
the migrating birds, the valley of flowers or the attacking shark evokes
awe and a deep sense of wonder. The ecological conflict and cooperation
among members of a population and among populations of a community
or even the molecular traffic inside a cell make us deeply reflect on – what
indeed is life? This question has two implicit questions within it. The first
is a technical one and seeks answer to what living is as opposed to the
non-living, and the second is a philosophical one, and seeks answer to
what the purpose of life is. As scientists, we shall not attempt answering
the second question. We will try to reflect on – what is living?
1.1 DIVERSITY IN THE LIVING WORLD
If you look around you will see a large variety of living organisms, be it
potted plants, insects, birds, your pets or other animals and plants. There
are also several organisms that you cannot see with your naked eye but
they are all around you. If you were to increase the area that you make
observations in, the range and variety of organisms that you see would
increase. Obviously, if you were to visit a dense forest, you would probably
see a much greater number and kinds of living organisms in it. Each
different kind of plant, animal or organism that you see, represents a
species. The number of species that are known and described range
between 1.7-1.8 million. This refers to biodiversity or the number and
THE LIVING WORLD
CHAPTER  1
1.1 Diversity in the
Living World
1.2 Taxonomic
Categories
2024-25
4 BIOLOGY
types of organisms present on earth. We should remember here that as
we explore new areas, and even old ones, new organisms are continuously
being identified.
As stated earlier, there are millions of plants and animals in the world;
we know the plants and animals in our own area by their local names.
These local names would vary from place to place, even within a country.
Probably you would recognise the confusion that would be created if we
did not find ways and means to talk to each other, to refer to organisms
we are talking about.
Hence, there is a need to standardise the naming of living organisms
such that a particular organism is known by the same name all over the
world. This process is called nomenclature. Obviously, nomenclature
or naming is only possible when the organism is described correctly and
we know to what organism the name is attached to. This is identification.
In order to facilitate the study, number of scientists have established
procedures to assign a scientific name to each known organism.  This is
acceptable to biologists all over the world. For plants, scientific names are
based on agreed principles and criteria, which are provided in International
Code for Botanical Nomenclature (ICBN). You may ask, how  are animals
named? Animal taxonomists have evolved International Code of Zoological
Nomenclature (ICZN). The scientific names ensure that each organism
has only one name. Description of any organism should enable the people
(in any part of the world) to arrive at the same name. They also ensure
that such a name has not been used for any other known organism.
Biologists follow universally accepted principles to provide scientific
names to known organisms.  Each name has two components – the
Generic name and the specific epithet. This system of providing a
name with two components is called Binomial nomenclature. This
naming system given by Carolus Linnaeus is being practised by biologists
all over the world. This naming system using a two word format was
found convenient. Let us take the example of mango to understand the
way of providing scientific names better. The scientific name of mango is
written as Mangifera indica. Let us see how it is a binomial name.  In this
name Mangifera represents the genus while indica, is a particular species,
or a specific epithet. Other universal rules of nomenclature are as follows:
1. Biological names are generally in Latin and written in italics.
They are Latinised or derived from Latin irrespective of their
origin.
2. The first word in a biological name represents the genus while
the second component denotes the specific epithet.
3. Both the words in a biological name, when handwritten, are
separately underlined, or printed in italics to indicate their Latin
origin.
2024-25
THE LIVING WORLD 5
4. The first word denoting the genus starts with a capital letter
while the specific epithet starts with a small letter. It can be
illustrated with the example of Mangifera indica.
Name of the author appears after the specific epithet, i.e., at the end of
the biological name and is written in an abbreviated form, e.g., Mangifera
indica Linn. It indicates that this species was first described by Linnaeus.
Since it is nearly impossible to study all the living organisms, it is
necessary to devise some means to make this possible. This process is
classification. Classification is the process by which anything is grouped
into convenient categories based on some easily observable characters.
For example, we easily recognise groups such as plants or animals or
dogs, cats or insects. The moment we use any of these terms, we associate
certain characters with the organism in that group. What image do you
see when you think of a dog ? Obviously, each one of us will see ‘dogs’
and not ‘cats’. Now, if we were to think of ‘Alsatians’ we know what we are
talking about. Similarly, suppose we were to say ‘mammals’, you would,
of course, think of animals with external ears and body hair. Likewise, in
plants, if we try to talk of ‘Wheat’, the picture in each of our minds will be
of wheat plants, not of rice or any other plant. Hence, all these - ‘Dogs’,
‘Cats’, ‘Mammals’, ‘Wheat’, ‘Rice’, ‘Plants’, ‘Animals’, etc., are convenient
categories we use to study organisms. The scientific term for these
categories is taxa. Here you must recognise that taxa can indicate
categories at very different levels. ‘Plants’ – also form a taxa. ‘Wheat’ is
also a taxa. Similarly, ‘animals’, ‘mammals’, ‘dogs’ are all taxa – but you
know that a dog is a mammal and mammals are animals. Therefore,
‘animals’, ‘mammals’ and ‘dogs’ represent taxa at different levels.
Hence, based on characteristics, all living organisms can be classified
into different taxa. This process of classification is taxonomy. External
and internal structure, along with the structure of cell, development
process and ecological information of organisms are essential and form
the basis of modern taxonomic studies.
Hence, characterisation, identification, classification and nomenclature
are the processes that are basic to taxonomy.
Taxonomy is not something new. Human beings have always been
interested in knowing more and more about the various kinds of
organisms, particularly with reference to their own use. In early days,
human beings needed to find sources for their basic needs of food, clothing
and shelter. Hence, the earliest classifications were based on the ‘uses’ of
various organisms.
Human beings were, since long, not only interested in knowing more
about different kinds of organisms and their diversities, but also the
relationships among them. This branch of study was referred to as
systematics. The word systematics is derived from the Latin word
‘systema’ which means systematic arrangement of organisms.  Linnaeus
2024-25