Life is a unique, complex organization of molecules, expressing through chemical reactions which lead to growth,
development, responsiveness, adaptation & reproduction.
A living organism is self-replicating, evolving and self-regulating interactive system capable of responding to external stimuli.
PROPERTIES OF LIVING ORGANISMS
1. Growth 3. Metabolism
• It is the increase in number & mass of cells by cell division. • It is the sum total of all biochemical reactions taking place
• In plants, growth continues throughout their lifespan. inside a living system.
• In animals, growth is only up to a certain age. However, • It is the defining feature of living organisms.
cell division occurs to replace lost cells. • Metabolic reactions can be demonstrated outside the body
• Basically, growth is the increase in mass & size. Thus non- in cell-free systems. Isolated metabolic reactions in vitro
living objects also grow (surface accumulation of material). are not living things but are living reactions.
So growth is not a defining property of living organisms.
4. Cellular organization
• In living organisms, growth is from inside.
• Organisms are made up of one or more cells.
2. Reproduction • It is the defining feature of living organisms.
• It is the production of progeny having features similar to
5. Consciousness
those of parents.
• Organisms reproduce asexually and sexually. • It is the ability of organisms to sense their environment and
• In unicellular organisms, growth & reproduction are same respond to environmental stimuli (like light, water,
because they reproduce by cell division. temperature, other organisms, chemicals, pollutants, etc).
• Many organisms do not reproduce (e.g. mules, worker • All organisms are ‘aware’ of their surroundings. So, it is the
bees, infertile human couples, etc). Hence, reproduction is defining property of living organisms.
not a perfect defining property of living organisms. • Human is the only organism having self-consciousness.
DIVERSITY IN THE LIVING WORLD
• The number and types of organisms present on earth refer • The first word is genus name (Generic name) and second
to biodiversity. word is the species name (specific epithet).
• Number of species described is 1.7-1.8 million. E.g. Homo sapiens- Homo represents the genus name and
• Taxonomy is the study of identification, classification & sapiens represents the species name.
nomenclature of organisms. • The Genus name starts with capital letter and the species
Systematics (Latin ‘systema’ = systematic arrangement) name starts with small letter.
deals with evolutionary relationships among organisms. • Name of the author (in abbreviated form) appears at the end
• Systema Naturae is the book written by Linnaeus. of the biological name.
Basic processes of taxonomy E.g., Mangifera indica Linn. It indicates that this species
• Characterization: It is the understanding of characters of was first described by Linnaeus.
organisms such as external and internal structure, structure of TAXONOMIC CATEGORIES
cell, development process, ecological information etc. - Classification involves hierarchy of steps in which each
• Identification: It is the correct description of the organism step represents a taxonomic category (rank).
so that the naming is possible. - All categories together constitute a taxonomic hierarchy.
• Classification: It is the grouping of organisms into - A group of organisms occupying a particular category is
convenient categories (taxa) based on characters. called a taxon (pl. taxa). E.g. Class Mammalia.
• Nomenclature (naming): It is the standardization of
- Each category or taxon represents a unit of classification.
names of the organisms such that an organism is known by Category Taxon
the same name all over the world. Kingdom Animalia
The system of naming with two components is called ↑ ↑
Binomial nomenclature. It is proposed by Linnaeus. Phylum/Division Chordata
Taxonomic ↑ ↑
Botanical names are based on the rules in International Class Mammalia
hierarchy in
Code for Botanical Nomenclature (ICBN). ↑ ↑
ascending order
Zoological names are based on International Code for Order Primata
↑ ↑
Zoological Nomenclature (ICZN). Family Hominidae
↑ ↑
Universal rules of Binomial nomenclature Genus Homo
• Scientific names are in Latin or Latinised and written in ↑ ↑
Species Sapiens
italics. When handwritten, they are underlined separately.
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development, responsiveness, adaptation & reproduction.
A living organism is self-replicating, evolving and self-regulating interactive system capable of responding to external stimuli.
PROPERTIES OF LIVING ORGANISMS
1. Growth 3. Metabolism
• It is the increase in number & mass of cells by cell division. • It is the sum total of all biochemical reactions taking place
• In plants, growth continues throughout their lifespan. inside a living system.
• In animals, growth is only up to a certain age. However, • It is the defining feature of living organisms.
cell division occurs to replace lost cells. • Metabolic reactions can be demonstrated outside the body
• Basically, growth is the increase in mass & size. Thus non- in cell-free systems. Isolated metabolic reactions in vitro
living objects also grow (surface accumulation of material). are not living things but are living reactions.
So growth is not a defining property of living organisms.
4. Cellular organization
• In living organisms, growth is from inside.
• Organisms are made up of one or more cells.
2. Reproduction • It is the defining feature of living organisms.
• It is the production of progeny having features similar to
5. Consciousness
those of parents.
• Organisms reproduce asexually and sexually. • It is the ability of organisms to sense their environment and
• In unicellular organisms, growth & reproduction are same respond to environmental stimuli (like light, water,
because they reproduce by cell division. temperature, other organisms, chemicals, pollutants, etc).
• Many organisms do not reproduce (e.g. mules, worker • All organisms are ‘aware’ of their surroundings. So, it is the
bees, infertile human couples, etc). Hence, reproduction is defining property of living organisms.
not a perfect defining property of living organisms. • Human is the only organism having self-consciousness.
DIVERSITY IN THE LIVING WORLD
• The number and types of organisms present on earth refer • The first word is genus name (Generic name) and second
to biodiversity. word is the species name (specific epithet).
• Number of species described is 1.7-1.8 million. E.g. Homo sapiens- Homo represents the genus name and
• Taxonomy is the study of identification, classification & sapiens represents the species name.
nomenclature of organisms. • The Genus name starts with capital letter and the species
Systematics (Latin ‘systema’ = systematic arrangement) name starts with small letter.
deals with evolutionary relationships among organisms. • Name of the author (in abbreviated form) appears at the end
• Systema Naturae is the book written by Linnaeus. of the biological name.
Basic processes of taxonomy E.g., Mangifera indica Linn. It indicates that this species
• Characterization: It is the understanding of characters of was first described by Linnaeus.
organisms such as external and internal structure, structure of TAXONOMIC CATEGORIES
cell, development process, ecological information etc. - Classification involves hierarchy of steps in which each
• Identification: It is the correct description of the organism step represents a taxonomic category (rank).
so that the naming is possible. - All categories together constitute a taxonomic hierarchy.
• Classification: It is the grouping of organisms into - A group of organisms occupying a particular category is
convenient categories (taxa) based on characters. called a taxon (pl. taxa). E.g. Class Mammalia.
• Nomenclature (naming): It is the standardization of
- Each category or taxon represents a unit of classification.
names of the organisms such that an organism is known by Category Taxon
the same name all over the world. Kingdom Animalia
The system of naming with two components is called ↑ ↑
Binomial nomenclature. It is proposed by Linnaeus. Phylum/Division Chordata
Taxonomic ↑ ↑
Botanical names are based on the rules in International Class Mammalia
hierarchy in
Code for Botanical Nomenclature (ICBN). ↑ ↑
ascending order
Zoological names are based on International Code for Order Primata
↑ ↑
Zoological Nomenclature (ICZN). Family Hominidae
↑ ↑
Universal rules of Binomial nomenclature Genus Homo
• Scientific names are in Latin or Latinised and written in ↑ ↑
Species Sapiens
italics. When handwritten, they are underlined separately.
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