Biology is the science, which deals with the study of living organisms and their life processes. The term 'Biology' was first introduced by GR Treviranus and Jean Baptiste de Lamarck (1802).
What is Living?
Living organisms show certain key characteristics which distinguish them from non-living things. These are
• Growth is shown by living organism by an increase in mass and an increase in the number of individuals. A multicellular organism grows by cell division.
• Reproduction is the process of producing offspring possessing features similar to those of their parents. It takes place by sexual or asexual mode.
• Metabolism comprises of both constructive reactions (anabolism) and destructive reactions (catabolism), continuously occurring in the body.
•Cellular organisation The cells are the building blocks of all living organisms may it be plants, animals or humans. Thus, organisms can be unicellular or multicellular.
• Consciousness is the ability of living organisms to sense their surroundings or environment and respond to these environmental stimuli, which could be physical, chemical and biological.
Diversity in the Living World
• Biodiversity refers to the number and types of organisms present on earth. Our earth possesses a wide range of living organisms. A number of plants and animals have been identified and described. However, a large number of organisms are still unknown to us.
• A rich diversity among organisms or biodiversity in terms of size, colour, habitat, physiological and morphological features can be observed on earth. Therefore, it is necessary to standardise the methods to identify and classify them on the basis of their defining characteristics.
Certain rules and principles have been formulated for the identification, nomenclature and classification of organisms, which facilitate the study of vast diversity of organisms present on earth.
• Identification involves the process of finding the correct name and place of an organism. The morphological and anatomical characters are examined for proper identification.
• Nomenclature involves standardising appropriate naming of living organisms, so that they can be recognised and differentiated from others easily across the world. To ease the process of studying different organisms, a scientific name is assigned to each organism.
The principles of naming have been established by International Code for Botanical Nomenclature (ICBN) and International Code for Zoological Nomenclature (ICZN) for plants and animals, respectively.
• Organisms are identified on the basis of their resemblance and distinct differences from others. They are assigned a correct scientific/biological name.
• Binomial System of Nomenclature was developed by Carolus Linnaeus in 1751 and was published in his book Species Plantarum (1753). As per this system, a biological name comprises of two words namely, generic name and the specific epithet.
• Nomenclature of organisms follows certain universal rules,
which are as follows
■ Biological names are generally in Latin and are written in Italics. These are latinised or derived from Latin irrespective of their origin.
Both the words in a biological name, when handwritten are separately underlined or printed in Italics to indicate their Latin origin.
• The first letter of the generic name is written in capital letter while that of specific epithet is written in small letter, e.g. Mangifera indica.
Name of the author appears after the specific epithet at the end of the biological name and is written in an abbreviated form, e.g. Mangifera indica Linn, where Linn is for Linnaeus.
Classification is the process by which organisms are grouped into convenient categories based on some easily observable characters. The scientific term used for different categories is taxa.
Taxonomy is the branch of science which deals with different aspects of identification, nomenclature and classification of organisms. Linnaeus is known as the Father of Taxonomy
⚫ Systematics is the study of systematic arrangement of organisms and the evolutionary relationships amongst them.
Taxonomic Categories
⚫ The system of arranging different categories or ranks, which are referred to as taxonomic categories in a proper ascending or descending order is called as taxonomic hierarchy. Every organism occupies a distinct position in a taxonomic hierarchy.
Each category in taxonomical hierarchy is commonly called taxon. The term 'taxon' was first introduced by ICBN during 1956 and it is the basic unit of classification. • Taxonomic hierarchy was first proposed by Linnaeus and
thus it is also called as Linnaeus hierarchy. This hierarchy
constitutes the following components in an ascending order.
• Species It is the smallest unit of taxonomic hierarchy
consisting of groups of morphologically similar individuals which can interbreed to produce offspring. e.g. nigrum and melongena are the two species of genus-Solanum.
Genus It comprises of a group of related species having more characters in common in comparison to species of other genera, e.g. lion, leopard and tiger are all species of the genus-Panthera, while cats belong to the genus-Felis.
Family It is a group of related genera with a few common features but less number of similarities as compared to genus and species. Plant families are categorised on the basis of both vegetative and reproductive features of species, e.g. family-Solanaceae possesses different genera like Solanum, Petunia and Datura. Similarly, in animals, cats and dogs belong to two different families-Felidae and Canidae, respectively.
. Order It is the assemblage of families which exhibit a few similar characters, e.g. order-Polymoniales contains different plant families like Solanaceae and Convolvulaceae. In animals, order-Camivora includes families Felidae and Canidae.
. Class It includes one or more related orders, e.g. class-Mammalia includes order-Primata and Camivora.
Phylum or Division It includes classes with a few similar characters, e.g. phylum-Chordata includes animals possessing notochord and dorsal neural system.
In plants, classes with few similar characters are placed under higher category called division, e.g. the division-Angiospermae includes wheat, onion, etc.
⚫ Kingdom It is the highest taxonomic category. All animals belong to the kingdom-Animalia, while all plants belong to the kingdom-Plantae.
Taxonomical Aids
Biologists have established certain procedures and techniques to store and preserve information as well as the specimens which are useful in identification and classification of organisms. These techniques stored information and procedures are called taxonomic tools or taxonomic aids. Following are some of the main taxonomical aids used to study taxonomy
⚫ Herbarium is the storehouse of collected plant specimens that are dried, pressed and presserved on herbarium sheets. The biggest herbarium of the world is the Royal Botanical Garden in Kew (England), while the biggest herbarium of India is the Central National Herbarium at Shibpur (Kolkata).
⚫ Botanical garden is essentially a collection of living plants maintained for both pure and applied studies. The famous botanical gardens are Royal Botanical Garden in Kew (England), Indian Botanical Garden, Howrah (India) and National Botanical Research Institute, Lucknow (India).
⚫ Museums have a collection of preserved plants and animals for study and reference purposes. Specimens are preserved in containers or jars in preservative solutions. Insects are preserved in insect boxes after collecting, killing and pinning them. Larger animals like birds and mammals are usually stuffed and
preserved.
⚫ Zoological parks are the places where wild animals are kept in protected environments under human care. This enables us to learn about their food habits and behaviour.
⚫ Keys are used for identification of plants and animals based on similarities and dissimilarities. The keys are based on the contrasting characters generally in a pair called couplet. Each statement in the key is called a lead. Keys are generally analytical in nature.
• Monograph contains information on any one taxon.
• Manuals are useful in providing information for identification of names of species found in an area.
⚫ Flora contains the actual account of habitat and distribution of plants of a given area.
⚫ Catalogue is a list that enumerates methodically all the species found in an area with brief description aiding identification.
Neet questions example
MCQ
1 The characteristics of growth include (a) increase in mass
(b) increase in number of individuals (c) Both (a) and (b)
(d) ability to reproduce
2 Plants grow throughout life by which method?
(a) Cell dedifferentiation (b) Cell differentiation
(c) Cell division
(d) None of the above
3 Growth in unicellular organisms can be observed by
(a) counting the mass of cultured cells
(b) analysing the amount of nutrients absorbed by living
organism (c) growth cannot be observed
(d) simply counting the number of cells under microscope during in vitro culture
4 In majority of higher animals and plants, reproduction
and growth are
(a) mutually exclusive events
(b) synonymous events (c) synonymous events during in vitro culture
(d) None of the above
5 Among the following, which is a common phenomenon exhibited by living and non-living
organisms to show the feature of growth?
(a) Increase in mass
(b) Cell division
(c) Increase in replication rate
(d) Cell differentiation
6 What kind of growth is exhibited by non-living
organisms?
(a) Accumulation of material on surface
(b) Accumulation of material inside
(c) Growth from inside
(d) None of the above
7 A true regeneration was observed in
(a) Hydra
(c) Sponges
(b) Planaria
(d) Amoeba
8 Which of the following set of organisms reproduce by fragmentation (asexual mode of reproduction)?
(a) Amoeba, fungi and earthworm
(b) Fungi, filamentous algae and protonema of mosses (c) Hydra, fungi, Amoeba and bacteria
(d) Earthworm, bacteria and fungi
9 Reproduction is synonymous with growth in which of
the following set of organisms? (a) Bacteria, unicellular algae and Amoeba
(b) Bacteria, Amoeba and fungi
(c) Unicellular algae and fungi
(d) Unicellular algae and filamentous algae
10 Why reproduction cannot be considered as an inclusive defining characteristic of all living organisms?
(a) Non-living organisms also reproduce
(b) Many living organisms are sterile
(c) Reproduction is synonym to growth in all organisms
(d) Both (a) and (b)
11 Which of the following characteristics is not a defining character of living organisms?
(a) Growth
(b) Growth and reproduction
(c) Reproduction
(d) Growth and metabolism
12 Metabolism can be best defined as (a) the process in which a chemical is formed inside the
body
(b) the process in which a chemical is destroyed inside the body
(c) the sum total of all chemical reactions occurring in the body (d) a complex construction process only
13 In which of the following, metabolic reactions take place?
(a) In living organisms only
(b) Both in living and non-living organisms
(c) In cell-free systems
(d) Both (a) and (c)
