NEET 2025 LECTURE NOTE - BIOLOGY [FIRST YEAR]
ZOOLOGY
CHAPTER 01
THE LIVING WORLD
Biology is the science of life and living process. It is the study of life on earth and the story of evolution
of living organism on earth. The word biology is originating from two greek words Bios-means life and
logos means study so biology is known as Life science.
Characteristics of living organisms
(i) Growth
It is increasing mass and increasing number of individuals (twin characteristics of growth).
In living organisms, growth is internal, ie, occurs by cell division
Multicellular organisms grow by cellular enlargement and cell division. Which contributes to an increase
in size of the cell and increase in no. of cells. So growth and reproduction are exclusive events
Plants show indeterminate or indefinite growth throughout their life span by meristematic cell.
Animals show definite growth pattern, ie. growth takes place only upto a particular age.
Unicellular organisms grow by the accumulation of protoplasmic content due to cellular enlargement
and their cell divides, so growth and reproduction are inclusive events.
Non-living things can also show an increase in size by the accumulation of materials on the outer
surface (External growth)
So, growth can not be taken as a defining property of living organisms
(ii) Reproduction
It is the capacity to produce young ones of their own kind. Reproduction maintains the continuity of
species.
In organisms, reproduction takes place by 2 ways
(a) Asexual : Uniparental
(b) Sexual : Biparental
In lower organisms, common reproductive mechanism is asexual. It is different in different organisms.
1) Binary fission - Bacteria
2) Budding - Yeast, Hydra
3) Regeneration - Planaria (Flat worms)
4) Fragmentation - Filamentous algae like spirogyra, Fungi, Protonema of moss
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5) Spore formation - Fungi, Bacteria
In unicellular organisms, reproduction is synonymous with growth, ie, increase in number of cells.
In higher organisms, common reproductive mechanisms is sexual, which involves formation and fusion
of gametes.
Some living organisms cant reproduce. (Mule, worker bees, Infertile human couples)
So, reproduction is also cannot be an inclusive defining character of living organism but, no non -living
objects can reproduce by itself.
(iii) Metabolism
The sum total of all biochemical reactions in a living cell
It may be
(i) anabolism ii) Catabolism
Constructive process Destructive process
(simple complex) (complex simple)
Eg: Photosynthesis, protein synthesis Eg: Cellular respiration/Oxidation of food material
No non-living object exhibits metabolism
Isolated metabolic reactions outside the body of an organism, performed in a test tube
(invitro) are not living things but only living reaction.
It is a defining property. Invitro is only a living reaction, but not living things
(iv) Cellular organisation
All living organisms are made up of basic structural and functional units ie, cells
It is a defining property of living organism.
In higher organisms, cells are organised into tissues, organs and to organs system.
Cell Tissues Organs Organ system organism
The property of tissue is not present in the constituent of cells, each level of organisation has its own
properties, that arise as a result of interactions among the consituent components.
(v) Consciousness
It is the ability of living organisms to sense their environment and surroundings and respond to it.
These external stimuli can be physical, chemical or biological.
Plants can respond to stimuli such as light, temperature water, etc (tropic movements, photoperiodic
requirements for flowering)
Animals are aware of their environment with the help of sense organs
Only human beings have self consciousness.
So it is a defining property of living organism
So organisms are self replicating, evolving and self regulating intractive systems capable of
responding to external stimuli.
144
, NEET 2025 LECTURE NOTE - BIOLOGY [FIRST YEAR]
Biodiversity
Biodiversity is the number and type of organism that seen in the biosphere. Each different kind of plant,
animal or organism that we can see represent a species. The number of species that are known and
described rangs between 1.7 – 1.8 million.
Systematics
It deals with diversity of living organisms and their inter-relationships (taxonomic and phylogenetic
relationships)
The word systematics was derived from the Latin word ‘systema’ which means the systematic
arrangement of living organisms
The word ‘systematics’ was coined by Carolus Linnaeus.
Taxonomy
Taxonomy is the principle and procedure of arranging organism to proper group based on similarity
and dissimilarity.
The word ‘taxonomy’ was coined by A.P. de Candolle
Father of taxonomy: Carolus Linnaeus
The basic process of taxonomy includes
Characterisation, Identification, classificationa and nomenclature
Earliest classification is based on ‘uses’ of various organism as sources of food clothing and shelter.
Modern taxonomic study include morphology, anatomy, cell structure developmental process and
ecological information.
Nomenclature
It is the system of providing name to an organism.
Vernacular nomenclature: Naming an organism by using local or regional language
Scientific nomenclature
Binomial nomenclature
A system of naming an organism by using 2 words: Genus name and species name
Proposed by Carolus Linnaeus
Reference books of Binomial system are Systema naturae, Species plantarum
Rules and Regulations
a) Biological names are in Latin
b) Each name has 2 parts: Genus name (generic epithet) and species name (specific epithet)
c) Genus name should start with capital letter and species name with small letter
d) Biological names is should be underlined seperately when handwritten and printed in italics
145
ZOOLOGY
CHAPTER 01
THE LIVING WORLD
Biology is the science of life and living process. It is the study of life on earth and the story of evolution
of living organism on earth. The word biology is originating from two greek words Bios-means life and
logos means study so biology is known as Life science.
Characteristics of living organisms
(i) Growth
It is increasing mass and increasing number of individuals (twin characteristics of growth).
In living organisms, growth is internal, ie, occurs by cell division
Multicellular organisms grow by cellular enlargement and cell division. Which contributes to an increase
in size of the cell and increase in no. of cells. So growth and reproduction are exclusive events
Plants show indeterminate or indefinite growth throughout their life span by meristematic cell.
Animals show definite growth pattern, ie. growth takes place only upto a particular age.
Unicellular organisms grow by the accumulation of protoplasmic content due to cellular enlargement
and their cell divides, so growth and reproduction are inclusive events.
Non-living things can also show an increase in size by the accumulation of materials on the outer
surface (External growth)
So, growth can not be taken as a defining property of living organisms
(ii) Reproduction
It is the capacity to produce young ones of their own kind. Reproduction maintains the continuity of
species.
In organisms, reproduction takes place by 2 ways
(a) Asexual : Uniparental
(b) Sexual : Biparental
In lower organisms, common reproductive mechanism is asexual. It is different in different organisms.
1) Binary fission - Bacteria
2) Budding - Yeast, Hydra
3) Regeneration - Planaria (Flat worms)
4) Fragmentation - Filamentous algae like spirogyra, Fungi, Protonema of moss
143
, STUDY CENTRE
5) Spore formation - Fungi, Bacteria
In unicellular organisms, reproduction is synonymous with growth, ie, increase in number of cells.
In higher organisms, common reproductive mechanisms is sexual, which involves formation and fusion
of gametes.
Some living organisms cant reproduce. (Mule, worker bees, Infertile human couples)
So, reproduction is also cannot be an inclusive defining character of living organism but, no non -living
objects can reproduce by itself.
(iii) Metabolism
The sum total of all biochemical reactions in a living cell
It may be
(i) anabolism ii) Catabolism
Constructive process Destructive process
(simple complex) (complex simple)
Eg: Photosynthesis, protein synthesis Eg: Cellular respiration/Oxidation of food material
No non-living object exhibits metabolism
Isolated metabolic reactions outside the body of an organism, performed in a test tube
(invitro) are not living things but only living reaction.
It is a defining property. Invitro is only a living reaction, but not living things
(iv) Cellular organisation
All living organisms are made up of basic structural and functional units ie, cells
It is a defining property of living organism.
In higher organisms, cells are organised into tissues, organs and to organs system.
Cell Tissues Organs Organ system organism
The property of tissue is not present in the constituent of cells, each level of organisation has its own
properties, that arise as a result of interactions among the consituent components.
(v) Consciousness
It is the ability of living organisms to sense their environment and surroundings and respond to it.
These external stimuli can be physical, chemical or biological.
Plants can respond to stimuli such as light, temperature water, etc (tropic movements, photoperiodic
requirements for flowering)
Animals are aware of their environment with the help of sense organs
Only human beings have self consciousness.
So it is a defining property of living organism
So organisms are self replicating, evolving and self regulating intractive systems capable of
responding to external stimuli.
144
, NEET 2025 LECTURE NOTE - BIOLOGY [FIRST YEAR]
Biodiversity
Biodiversity is the number and type of organism that seen in the biosphere. Each different kind of plant,
animal or organism that we can see represent a species. The number of species that are known and
described rangs between 1.7 – 1.8 million.
Systematics
It deals with diversity of living organisms and their inter-relationships (taxonomic and phylogenetic
relationships)
The word systematics was derived from the Latin word ‘systema’ which means the systematic
arrangement of living organisms
The word ‘systematics’ was coined by Carolus Linnaeus.
Taxonomy
Taxonomy is the principle and procedure of arranging organism to proper group based on similarity
and dissimilarity.
The word ‘taxonomy’ was coined by A.P. de Candolle
Father of taxonomy: Carolus Linnaeus
The basic process of taxonomy includes
Characterisation, Identification, classificationa and nomenclature
Earliest classification is based on ‘uses’ of various organism as sources of food clothing and shelter.
Modern taxonomic study include morphology, anatomy, cell structure developmental process and
ecological information.
Nomenclature
It is the system of providing name to an organism.
Vernacular nomenclature: Naming an organism by using local or regional language
Scientific nomenclature
Binomial nomenclature
A system of naming an organism by using 2 words: Genus name and species name
Proposed by Carolus Linnaeus
Reference books of Binomial system are Systema naturae, Species plantarum
Rules and Regulations
a) Biological names are in Latin
b) Each name has 2 parts: Genus name (generic epithet) and species name (specific epithet)
c) Genus name should start with capital letter and species name with small letter
d) Biological names is should be underlined seperately when handwritten and printed in italics
145
