Life
Life can be defined as a coordinated system of physical, chemical and biological activities, which leads to growth, development and reproduction. Living beings are called as organisms.
Features of living organisms
(i) Growth: All living organisms show growth. It is the irreversible increase in the mass and number of cells.
Plants grow continuously by cell division throughout their life span.
Animals grow up to certain age. However cell division occurs to replace the lost cells.
Unicellular organisms grow by cell division.
In living organisms growth is intrinsic or internal.
Non-living objects like mountains, boulders and sand mounds show growth, as matter added on them. This is the eccentric growth.
Hence growth cannot be considered as a defining property of living organisms.
(ii) Reproduction: Reproduction is the production of young ones or progeny of the same kind by the living organisms. Reproduction may be by sexual or asexual method.
Sexual reproduction takes place by the fusion of gametes.
Asexual reproduction takes place by various means like,
a) Spores: Some lower organisms like fungi produce millions of spores which give rise to new individual upon getting suitable conditions.
b) Budding: Lower organisms like unicellular organisms, reproduce by budding. e.g. Yeast
c) Fragmentation: Some animals reproduce by regenerating the whole new organism from the fragmented part. e.g. Planaria
d) Binary Fission: Unicellular organisms divides into two independent organisms. e.g. Amoeba
In unicellular organisms, growth is synonymous with reproduction i.e. increase in number occurs simultaneously as they reproduce. There are many living organisms that do not reproduce (e.g. sterile worker honey bees, Mule). Hence reproduction is not considered as inclusive defining characteristic of living organisms.
(iii) Metabolism: All chemical reactions that occur in a cell are called metabolism.
There are two forms of metabolism,
a) Anabolism: It is the constructive part of the metabolism where the reaction leads to the formation of materials. e.g. Photosynthesis.
b) Catabolism: It is the destructive part of the metabolism where the reaction leads to the breakdown of materials. e.g. Respiration.
Metabolism is the defining feature of all living organisms without exception.
(iv) Cellular organisation: All living organisms are made up of cells.
In unicellular organisms, the single cell performs all the vital activities of life.
In multicellular organisms, cells join together to perform various functions.
Cellular organisation is the defining feature of the life forms.
(v) Response to stimuli: All living organisms respond to external stimulus and they have sense of their surroundings.
They develop adaptations to suit the environment changes and gradually evolve into new type of organisms.
Human being is the only organism who is aware of himself i.e. self-conscious.
(vi) Homeostasis: The capacity of living organisms to maintain a steady internal environment is called homeostasis.
(vii) Death: Death is a biological event that occurs due to permanent breakdown of body function.
All the organisms are mortal and have a lifespan.
But unicellular organisms are considered as immortal, as a single cell divides into two daughter cells. There is no natural death for unicellular organisms.
“Living organisms are self-replicating, evolving and self-regulating interactive systems, capable of responding to external stimuli”
Diversity in the living world
There is a great diversity of life in nature.
The present day organisms are the end product of about 3 billion years of evolution.
A general estimation of number of species of living organisms, existing today are about 5-30millions.
Half of these are found in unexplored tropical rain-forests of the world. It covers only 8% of earth but is rich of biodiversity.
The number of species that are known and described, range between 1.7-1.8 million.
Natural diversity of the life on earth in called as biological diversity or biodiversity.
There are millions of plants and animals in the world. We know them by their local names, which vary from place to place. Hence, there is a need to standardize the naming of living organisms so that, a particular organism is known by same name throughout the world.
Taxonomy: The science of identification, nomenclature and classification of organisms, is called taxonomy.
Systematics: It is the science that deals with the arrangement of organisms, in an organized way according to their features.
Systematics and taxonomy are used as synonyms.
Taxonomy includes Identification, nomenclature and classification.
Identification: The determination of an organism being identical to another already known organism, is called Identification.
Nomenclature: The process of giving name to the organism is called nomenclature.
The names are either vernacular names or scientific names.
(i) Vernacular names have some drawbacks because, they are in local language and hence cannot be understandable throughout the world. Same name is often used for many species.
(ii) Scientific names are acceptable all over the world, as they are given based on agreed principle and criteria.
Classification: The method of arranging and grouping of organisms into various divisions is called classification.
Types of classification
1. Artificial system: The classification is based on one or two distinguishing characters.
Plants were classified based on their height only into groups like herbs, shrubs and trees. Unrelated plants were grouped together.
This system is discarded because, unrelated organisms come under one heading which have no natural relationship.
2. Natural system: It is based on important biological similarities of organisms.
In this system many characters considered so that evolutionary significance is clear.
The organism with maximum possible number of common features are grouped to the same species.
The similarities of morphology, anatomy, cell structure, comparative osteology, DNA, serum and certain chemicals are taken into consideration.
3. Phylogenetic system: It is based on evolutionary relationships.
The evolutionary history of particular organism is called phylogeny.
The classification which is based on phylogenetic relationships is called evolutionary classification.
The present natural system of classification are made on some facts of evolution evidences. Phylogenetic classification was given by Engler and Prantle.
Binomial nomenclature
Carolus Linnaeus introduced the binomial system of nomenclature. He proposed scientific names for all the plants and animals. He is known as Father of taxonomy.
In this method, every organism is given a scientific name which has two parts:
The first is the name of genus called generic name and the second is the name of the species called specific epithet.
Ex: Mangifera indica and Homo sapiens.
In the above given example, Mangifera and Homo are the generic names whereas, indica and sapiens are the specific names.
The rules of nomenclature are framed and standardised by international committees like,
ICBN- International Code for Botanical Nomenclature for plants
ICZN- International Code for Zoological Nomenclature for animals
ICVN- International Code for Viral Nomenclature for viruses
ICNB- International Code for Nomenclature of Bacteria
ICNCP- International Code for Nomenclature of Cultivated Plants.
Universal Rules of Nomenclature
(i) Biological names are generally in Latin or derived from Latin, irrespective of their origin.
(ii) The first word represents the generic name and the second word represents specific epithet.
(iii) The generic name starts with a Capital letter and specific name starts with small letter only.
(iv) The scientific names are underlined separately if handwritten and italicized if printed.
(v) The name of the author is written in an abbreviated form after specific name.
(vi) When the scientific name is changed for some reason, the original author's name is given in parenthesis.
Life can be defined as a coordinated system of physical, chemical and biological activities, which leads to growth, development and reproduction. Living beings are called as organisms.
Features of living organisms
(i) Growth: All living organisms show growth. It is the irreversible increase in the mass and number of cells.
Plants grow continuously by cell division throughout their life span.
Animals grow up to certain age. However cell division occurs to replace the lost cells.
Unicellular organisms grow by cell division.
In living organisms growth is intrinsic or internal.
Non-living objects like mountains, boulders and sand mounds show growth, as matter added on them. This is the eccentric growth.
Hence growth cannot be considered as a defining property of living organisms.
(ii) Reproduction: Reproduction is the production of young ones or progeny of the same kind by the living organisms. Reproduction may be by sexual or asexual method.
Sexual reproduction takes place by the fusion of gametes.
Asexual reproduction takes place by various means like,
a) Spores: Some lower organisms like fungi produce millions of spores which give rise to new individual upon getting suitable conditions.
b) Budding: Lower organisms like unicellular organisms, reproduce by budding. e.g. Yeast
c) Fragmentation: Some animals reproduce by regenerating the whole new organism from the fragmented part. e.g. Planaria
d) Binary Fission: Unicellular organisms divides into two independent organisms. e.g. Amoeba
In unicellular organisms, growth is synonymous with reproduction i.e. increase in number occurs simultaneously as they reproduce. There are many living organisms that do not reproduce (e.g. sterile worker honey bees, Mule). Hence reproduction is not considered as inclusive defining characteristic of living organisms.
(iii) Metabolism: All chemical reactions that occur in a cell are called metabolism.
There are two forms of metabolism,
a) Anabolism: It is the constructive part of the metabolism where the reaction leads to the formation of materials. e.g. Photosynthesis.
b) Catabolism: It is the destructive part of the metabolism where the reaction leads to the breakdown of materials. e.g. Respiration.
Metabolism is the defining feature of all living organisms without exception.
(iv) Cellular organisation: All living organisms are made up of cells.
In unicellular organisms, the single cell performs all the vital activities of life.
In multicellular organisms, cells join together to perform various functions.
Cellular organisation is the defining feature of the life forms.
(v) Response to stimuli: All living organisms respond to external stimulus and they have sense of their surroundings.
They develop adaptations to suit the environment changes and gradually evolve into new type of organisms.
Human being is the only organism who is aware of himself i.e. self-conscious.
(vi) Homeostasis: The capacity of living organisms to maintain a steady internal environment is called homeostasis.
(vii) Death: Death is a biological event that occurs due to permanent breakdown of body function.
All the organisms are mortal and have a lifespan.
But unicellular organisms are considered as immortal, as a single cell divides into two daughter cells. There is no natural death for unicellular organisms.
“Living organisms are self-replicating, evolving and self-regulating interactive systems, capable of responding to external stimuli”
Diversity in the living world
There is a great diversity of life in nature.
The present day organisms are the end product of about 3 billion years of evolution.
A general estimation of number of species of living organisms, existing today are about 5-30millions.
Half of these are found in unexplored tropical rain-forests of the world. It covers only 8% of earth but is rich of biodiversity.
The number of species that are known and described, range between 1.7-1.8 million.
Natural diversity of the life on earth in called as biological diversity or biodiversity.
There are millions of plants and animals in the world. We know them by their local names, which vary from place to place. Hence, there is a need to standardize the naming of living organisms so that, a particular organism is known by same name throughout the world.
Taxonomy: The science of identification, nomenclature and classification of organisms, is called taxonomy.
Systematics: It is the science that deals with the arrangement of organisms, in an organized way according to their features.
Systematics and taxonomy are used as synonyms.
Taxonomy includes Identification, nomenclature and classification.
Identification: The determination of an organism being identical to another already known organism, is called Identification.
Nomenclature: The process of giving name to the organism is called nomenclature.
The names are either vernacular names or scientific names.
(i) Vernacular names have some drawbacks because, they are in local language and hence cannot be understandable throughout the world. Same name is often used for many species.
(ii) Scientific names are acceptable all over the world, as they are given based on agreed principle and criteria.
Classification: The method of arranging and grouping of organisms into various divisions is called classification.
Types of classification
1. Artificial system: The classification is based on one or two distinguishing characters.
Plants were classified based on their height only into groups like herbs, shrubs and trees. Unrelated plants were grouped together.
This system is discarded because, unrelated organisms come under one heading which have no natural relationship.
2. Natural system: It is based on important biological similarities of organisms.
In this system many characters considered so that evolutionary significance is clear.
The organism with maximum possible number of common features are grouped to the same species.
The similarities of morphology, anatomy, cell structure, comparative osteology, DNA, serum and certain chemicals are taken into consideration.
3. Phylogenetic system: It is based on evolutionary relationships.
The evolutionary history of particular organism is called phylogeny.
The classification which is based on phylogenetic relationships is called evolutionary classification.
The present natural system of classification are made on some facts of evolution evidences. Phylogenetic classification was given by Engler and Prantle.
Binomial nomenclature
Carolus Linnaeus introduced the binomial system of nomenclature. He proposed scientific names for all the plants and animals. He is known as Father of taxonomy.
In this method, every organism is given a scientific name which has two parts:
The first is the name of genus called generic name and the second is the name of the species called specific epithet.
Ex: Mangifera indica and Homo sapiens.
In the above given example, Mangifera and Homo are the generic names whereas, indica and sapiens are the specific names.
The rules of nomenclature are framed and standardised by international committees like,
ICBN- International Code for Botanical Nomenclature for plants
ICZN- International Code for Zoological Nomenclature for animals
ICVN- International Code for Viral Nomenclature for viruses
ICNB- International Code for Nomenclature of Bacteria
ICNCP- International Code for Nomenclature of Cultivated Plants.
Universal Rules of Nomenclature
(i) Biological names are generally in Latin or derived from Latin, irrespective of their origin.
(ii) The first word represents the generic name and the second word represents specific epithet.
(iii) The generic name starts with a Capital letter and specific name starts with small letter only.
(iv) The scientific names are underlined separately if handwritten and italicized if printed.
(v) The name of the author is written in an abbreviated form after specific name.
(vi) When the scientific name is changed for some reason, the original author's name is given in parenthesis.
0 Comments