The Living World

 

The Living World

There is no clear cut distinction between living and non-living things. The organisms like viruses are non-living by themselves but become active and multiply when they are inside the living cells. They are neither plants nor animals but have hereditary material of their own. The prions do not even have the hereditary material and propagate diseases like Kuru and Madcow

The living organisms occur almost in every habitat on earth. We can find them from cold mountains to hot springs. A wide range of the living organisms can be found in fresh or marine water bodies and forests. The living forms as compared to non-livings have some fundamental characteristics. They are defined as ‘the self-replicating, self evolving with self-regulating interactive systems capable of responding to external stimuli’. All living organisms- the past, the present and the future, are linked to one another by sharing the common genetic material.

Following are the important distinctive characteristics exhibited by living forms.

Growth

The increase in mass and increase in the number of individuals are twin characteristics of growth. The multi- cellular organisms grow by cell division. The animals grow up to a certain age, whereas the plants grow throughout their life. The cell division also occurs to replace lost cells. The unicellular organisms also grow by cell division but there it is a type of reproduction. In multicellular organisms, whether animals or plants, the growth and reproduction are mutually exclusive events. Though the non-livings, like mountains, sand mounds and snow also grow, if we consider the increase in body mass as criterion, but this growth is by accumulation of material on the surface, and not from inside as we see in animals. So, growth alone cannot be considered as a defining property of living organisms until and unless it is well specified.

Reproduction

The living organisms reproduce asexually as well as sexually to multiply their number. Fungi reproduce asexually by spore formation. The lower organisms, like Hydra and Yeast, reproduce by budding. In Planaria (flat worm), there is fragmentation and regeneration of lost parts. In unicellular forms, as described above, the reproduction is synonymous with growth. Moreover, there are living organisms who do not reproduce, e.g., mule, worker honey bee or infertile human. Thus, the reproduction, like growth, can also not be taken as defining characteristic of the living forms. On the other hand, this is however true, that non-living objects are not capable of reproducing or replicating themselves.

Budding in Hydra

Fragmentation in Planaria

       (a) Budding in Hydra;               (b) Fragmentation in Planaria

Metabolism

All living organisms are constantly making or breaking biomolecules. Such conversions are due to chemical reactions, and sum total of all such chemical reactions, occurring in the body is called metabolism. The metabolic reactions can be anabolic (constructive) or catabolic (destructive).

In Catabolism the energy is released by the break down of complex material into simpler ones. In cellular respiration, the breaking down of glucose into carbon-di-oxide and water to release energy, is an example of catabolism.

In Anabolism the complex material is synthesized from simpler ones. The photosynthesis, in which glucose/starch is synthesized from carbon-di-oxide and water, is an example of anabolism

Each metabolic pathway in the cell is tightly regulated by enzymes (both activators and inhibitors)

The non-living objects do not exbibit metabolism. The isolated metabolic reactions invitro do not make the things living.

Consciousness

All the living organisms can sense their surroundings and respond to these environmental stimuli. The stimuli can be physical, chemical or biological. From lower to higher organisms there are various types of sensory structures. The photoperiod affects the seasonal breeders, both plants and animals. All organisms are conscious or aware of their surroundings. Human is the only organism who is aware of himself also, and thus has ‘self-consciousness’ Such self-consciousness is lacking in patients who are lying in ‘coma’ and are brain-dead.

Cellular organization

All organisms, from prokaryotes to the most complex eukaryotes have cellular organization. The cell may be simple or highly specialized for the required function. Such cellular organization is not exhibited by non-living objects. Hence, the cellular organization of the body is the defining feature of all living forms.

There is great diversity (biodiversity) in the number and types / variety of organisms present on earth.

Homeostasis

It is the maintenance of constancy in the internal conditions (steady state), different from the environment.

All organisms maintain within narrow limits the levels of salts, glucose, carbon-di-oxide, oxygen, calcium etc. in the intercellular matrix.

Homeostasis is the fundamental property of living beings.

Most of the lower vertebrates (fi shes, amphibians and reptiles) lose most of their heat energy to their environment. These vertebrates are called Ectotherms. These animals depend on the their environment for temperature regulation. At low temperature in the surrounding, their body temperature is also dropped and they become cold. Such animals are, therefore, also called as Cold-blooded animals or Poikilotherms.

The higher vertebrates, i.e. birds and mammals, have developed special devices to retard the heat loss to the environment. Their body temperature remains nearly constant and generally higher than the surroundings. Such animals are called Warm- blooded animals or Homeotherms. Since these animals retain thermal energy in the body, they are also known as Endotherms.

In mammals when the surrounding temperature is low the peripheral blood vessels constrict to prevent heat loss, and the blood is diverted to the deeper parts of the body. When the ambient (surrounding) temperature is higher, the superficial blood vessels dilate and a part of heat is lost by radiation.

We have sensory receptors (modified dendrites of neurons) which perceive coldness (Krause end bulbs) and hotness (End bulbs of Ruffini). The information from such receptors reach hypothalamus, the thermoregulatory centre of the brain. The body temperature can be decreased by vasodilatation of superficial blood vessels, and by sweating. The body temperature can be increased by vasoconstriction of superficial blood vessels and by Shivering (Contraction of skeletal muscles). Since the change in body temperature is in reverse direction or to the negative side of the ambient temperature; such a control system is called Negative Feed Back Loop.

Adaptations

Adaptations are the results of natural selection and make the organisms better suited to their environment. The adaptations may be structural, physiological or behavioural

• Birds use wings for flight – Volant adaptations.
• Spiders design web for trapping the flying insects, i.e. their prey.
• Night blooming flowers are white and emit scent for attracting pollinating insects.
• Some desert plants are leafless and are adapted for conservation of moisture (water).
• Humming birds have extremely narrow and long beak and while hovering, suck the nectar of such flowers which do not have landing platforms.
• Certain species of orchids resemble in shape, colour and odour of females of certain bees and flies. Such male bees or flies mistakenly attempt to copulate with orchids, and in the attempt transfer the pollen grains from one flower to the other.

Adaptation can be short-term and long-term type.

1. Short Term Adaptations –

These adaptations persist for shorter duration and completely disappear when the stimulus is removed.

• Darkening of skin when exposed to sun
• Rosy cheeks in hilly people
• Turning of shoot towards light
• Low metabolic rate in animals during hibernation
• Dormancy in seeds
• Geotropism in plants

1. Long Term Adaptations –

Such adaptations are permanent and persist even in the absence of stimuli.

• Development of beaks, claws and feathers in birds
• Development of heel in human
• Use of tail as fifth limb in Kangaroo
• Opposable thumb in human
• Scent in night blooming flowers
• Necessity of mammalian blood protein for egg laying in Anopheles mosquitoes.

Death

Organisms reproduce to compensate death or loss of life. When the organisms die, the microorganism decompose the body. The elements which constitute the body are freed and are returned to the ecosystem. Such cycling of elements between living and non-living maintains the balance in nature.

Following are the advantages of death:

1. It avoids overcrowding and maintains homeostasis.
2. It returns minerals to the soil and maintains balance.
3. The cellular death is essential for making the skin germ-proof.
4. The cellular death is also essential for the metamorphosis in tadpole.

Stages of Deaths

1. Clinical death – It is the stoppage of heart beat and breathing process.
2. Biological death – It is the death of cells and tissues.

The removal of organs, if needed for transplantation, is done after clinical death but before biological death.

BIOLOGICAL ORGANIZATION

• The biological organization starts with submicroscopic molecular level and ends up in ecosystem and the biosphere.
• Atom is the lowest unit at molecular level whereas the cell is the lowest unit at organism level.

The organization levels, below and above individual level, can be given as:

IMPORTANT ACHIEVEMENTS MADE BY SCIENTISTS BIOLOGISTS UPTO 19TH CENTURY

Aristotle (384BC- 322BC) – A Greek philosopher and a student of Plato

• He classified organisms on the basis of complexity in structure and function into a hierarchy, Scala natura, the ladder of life
• He wrote Historia Animalium and De Generatione Animalium
• He is known as the father of Biology/ Zoology/ Embryology

Andreas Vesalius (1514-1564) – A Belgian scientist.

• He is known as the ‘Father of Anatomy’.
• He wrote De Humani Corporis Fabrica (the structure of human body)

William Harvey (1578 -1657) – A British Scientist.

• He discovered blood-circulation. His monograph was named ‘Anatomical Exercise on the motion of the heart and blood’. He is known as the ‘Father of blood circulation’.
• He also studied reproduction and development in chick.

Robert Hooke (1635 – 1703 ) – A British Scientist.

• He first coined the term cellulae (cell) in 1665 by observing slice of cork under self made simple microscope.
• His book is named ‘Micrographia’

Antony Van Leeuwenhoek ( 1632-1723 ) – A Dutch cloth merchant .- turned into a scientist.

• He invented a simple microscope and studied living cells.
• He drew the diagram of bacteria and studied Euglena, sperms, blood corpuscles and compound eyes of insects.

Carolus Linnaeus (1707-1778) – A Swedish Naturalist .

• He published ‘Species Plantarum’ (6000 species of plants) and Systema Naturae( 4000 species of animals ) .in 1758
• He also reported Binomial nomenclature, in Philosophia Botanica in 1751, for naming plants and animals.

Georges Leopold Cuvier (1769-1832) – A French Palaeontologist .

• He rejected traditional Scala Naturae of Aristotle.
• He studied fossils and laid the foundation of Palaeontology. He is known to be the ‘Father of Modern Palaeontology’.
• He also studied comparative anatomy.

Jean Baptiste Lamarck (1744 -1829) – A French Naturalist.

• He was the first to discard the idea of fixity of species.
• He is known to be the ‘Father of evolutionary theories’. He wrote Philosophie Zoologique in 1809.
• He introduced the term ‘Biology’ (with Treviranus)

Robert Brown (1773-1858) –

• He discovered ‘Brownian movement’ in cytoplasm (1828).
• He also discovered ‘Nucleus’ in the cell.

Matthias Schleiden (1804-1881) – A German Botanist

• He Proposed cell theory in 1838 on the basis of his study on plant tissues.

Theodor Schwann (1810-1882) – A German Zoologist .

• He strengthened cell theory in 1839 by his study on animal tissues.

O. Hertwig (1875) –

• He studied fusion of nuclei during fertilization.
• He also proposed ‘protoplasmic theory’ to elaborate schultze’s hypothesis that ‘protoplasm is the physical basis of life’.
• He also coined the term ‘cytology’.

Charles Robert Darwin (1809 – 1882 ) – A British Naturalist .

• His book ‘The origin of species by means of natural selection’ was published in 1859.
• He is called ‘Newton of Biology’.
• He proposed the ‘Theory of Pangenesis’ to explain inheritance in the book ‘On the variation of animals and plants under domestication (1868)’

Rudolf C. Virchow (1858) –

• He proposed ‘Omnis cellula e cellulae’, i.e., New cells arise from pre-existing cells.
• He also suggested that disease is the pathological condition of cells.

Louis Pasteur (1822 – 1895 ) – A French Scientist.

• He proved that fermentation is caused by living organisms (Yeast and Bacteria).
• He established ‘Germ theory of diseases’.
• He discovered vaccine against Anthrax (caused by Bacillus anthracis in cattle ).
• He discarded ‘Spontaneous theory’ of origin of life.
• He also proposed Pasteurization for sterilization ( killing of germs )

Ernst Haeckel –

• He introduced 2-kingdoms, ‘Monera’ & ‘Protista’.
• He also coined and fully defined the term ‘Ecology’.

Gregor Johann Mendel (1822 – 1884 ) – An Austrian Monk

• He discovered principles of inheritance after his work on Pisum sativum, and published them in 1866.
• Mendel is known to be the ‘Father of genetics’.

August Weismann (1834 – 1914 ) – A German Biologist

• He rejected Lamarck’s concept of ‘Inheritance of acquired characters’ and Darwin’s theory of Pangenesis, with the discovery of ‘Theory of Germ plasm’ in 1892.

IMPORTANT ACHIEVEMENTS MADE BY SCIENTISTS BIOLOGISTS UPTO 20TH CENTURY

Hugo de Vries (1900)- A Dutch Geneticist

• He rediscovered Mendel’s laws with Tschermak (Austrian) and Correns (German) geneticists.
• He also proposed the ‘Theory of Mutation’.

Walter Sutton (1904)- An American Geneticist

• He discovered the chromosomal basis of heredity.

William Bateson (1909) -A British Biologist

• He introduced the term ‘Genetics’ and discovered linkage.

T. H. Morgan (1910) -An American Geneticist

• He discovered sex-linked inheritance and described the phenomenon of linkage and crossing over.

Alexander Flemming (1928) -A Scottish Bacteriologist

• Discovered Penicillin, an antibiotic from Penicillium notatum, which contaminated the culture of Staphylococcus bacteria.
• Penicillin was the first antibiotic used in world-war second.

Oswald Theodore Avery (1944) – An American Bacteriologist

• He discovered that genes are composed of DNA.

James Watson (1953) -An American, A Britisher

• They discovered double helical and Francis Crick structure of DNA.

H.G. Khorana, Robert Holley and Marshall Nirenberg (1968) – A Pakistani, An Americans

• Khorana synthesized a string of nucleotides in laboratory (First man-man-made gene).

The three scientists shared the noble prize for their work on genetic code and protein

synthesis.

Norman E. Borlaug (1970) – Associated to Green revolution and won Nobel Prize.

Stanley Cohen and Herbert Boyer (1973) -American Biochemists

• They discovered recombinant DNA – (rDNA) technology- a break through for modern biotechnology.

Ian Willmut and Campbell (1996) – Scottish embryologists

• Produced fi rst live clone of a sheep – ‘Dolly’

Human Genome project was launched in 1990 by US department of energy and National institute of health. In 2001 they identified all the, approximate 25,000 to 30,000 (3 × 104) genes in human DNA consisting of 3-billion (3 × 109) base pairs.

IMPORTANT ACHIEVEMENTS MADE BY SCIENTISTS BIOLOGISTS UPTO 21ST CENTURY

Paul C. Lauterbur, Sir Peter Mansfield (2003) – First American and second British

• Made discovery concerning MRI
• They were awarded Nobel prize in Physiology or Medicine

Barry J. Marshall, J. Robin Warren (2005) – Australians

• Made discovery regarding the role of Helicobacter pylori in Gastritis and Peptic ulcer.
• They were awarded Nobel prize in Physiology or Medicine

Andrew Z. Fire, Craig C. Mello (2006) – Americans

• They discovered RNA- interference- gene- silencing by RNAds
• They were awarded Nobel prize in Physiology or Medicine

Harald zur Hausen, Françoise Barré-Sinoussi, Luc Montagnier (2008) – First German, other two French

• Made discovery regarding Human Papilloma Virus and Human Immunodeficiency Virus.
• They were awarded Nobel prize in Physiology or Medicine

Osamu Shimomura, Martin Chalfie, Roger Y. Tsien (2008) – First Japanese and other two Americans

• Made discovery concerning Green fluorescent Protein.
• They were awarded Nobel prize in Chemistry

Venkatraman Ramakrishnan, Thomas A. Steitz, Ada E. Yonath (2009) – First Indian, second American and last Israely

• Made studies on structure and functions of ribosomes
• They were awarded Nobel prize in Chemistry

Bruce A. Beutler, Jules A. Hoffmann, Ralph M. Steinman (2011) – First American, second Luxembourger and third Canadian

• Made important discovery regarding Innate and Adaptive Immunity
• They were awarded Nobel prize in Physiology or Medicine

BIOLOGICAL STUDY AND ITS IMPORTANT BRANCHES

• Biology has been divided into two branches, i.e. Zoology and Botany.
• Science of microbiology was created by the invention of microscope in 16th century.
• A vast number of animals and plant have been arranged / classified on the basis of evolutionary relationships.
• International code of classification are known for animals, plants and bacteria etc.

Aquaculture

• It is the production of useful fauna and flora such as algae, fishes, prawn, pearl-oyster etc., at commercial level by utilizing small and large water bodies.

Biochemistry

• It is the study of chemistry of biological processes in the living organisms.
• It is also known as physiological chemistry or biological chemistry.

Biophysics

• It is application of various tools, techniques, methods and principles of physics for the study of biological processes.

Cell Biology

• It is the study of life processes of cell and their co-relation with the cell structure. It primarily depends on biochemical techniques.

Cryopreservation (cryobiology)

• It is preservation of living forms at very low temperature; or effect of low temperature on living forms.

Cytology

• It is the study of structure and composition of cells.

Demography

• It is statistical study of population dynamics

Dysteleology

• It is study of rudimentary organs

Ecology

• It is the study of relationship of organisms to their physical environment as well as to one another.

       (a) Auto-ecology – It is the study of individual organisms or single species.

       (b) Synecology – It is the study of group of organisms.

Embryology

• It is the study of individual development (ontogeny) from egg to hatching/birth. (‘Developmental Biology’ covers the development upto sexual maturity or adulthood).

Entomology

• It is the study of insects.

Ethnology

• It is study of human races

Ethology It is the study of animal behaviour in relation to body functioning, ecology and evolutionary aspects.

Evolutionary Biology

• It is the study of changes in living organism with the passage of time.

Exobiology

• This field of biology is related to the search of life outside the earth and within the solar system.

Fisheries

• The rearing, harvesting and marketing the commercially important aquatic fauna. The important fisheries are molluscan fisheries, Crustacean fisheries, sponge fisheries, Esturine fisheries etc. Inland fisheries (in fresh water).

Genetics

• It is Study of mechanism of inheritance and maintenance of hereditary
• characters.

Gerontology

• It is scientific study of ageing or senescence. Its foundation was laid
• down by Valdimir Korenchevsky.

Histology

• It is the study of structural organization of living beings at tissue level.

The micro technique (Microtomy) used for histology, includes following steps.

1. Fixation of tissue – (To maintain architecture of cells, or to stabilize the proteins.)

2. Dehydration – (Removal of water for preventing decomposition)

3. Paraffin embedding-

4. Slicing/ sectioning- (Done with the help of microtome)

5. Dewaxing

6. Staining

7. Mounting

Ichthyology

• Biological study of fishes

Karyology

• It is the study of cell-nucleus (Karyosome)

Limnology

• The study of fresh water bodies (ecosystem) especially lakes.

Marine Biology

• It is the study of Ocean (Marine) animals and plants and their ecological
• relationship.

Molecular biology

• It is the study of molecular organization (inorganic and organic molecules
• in the cells) of the organism. The term molecular biology was given for
• the first time by a British scientist, W.T. Astbury (1898-1961).

Morphology

• It is the study of body structure. The internal morphology is also called
• anatomy.

Myrmecology

• It is scientific study of Ants

Oncology

• It is the study of cancer

Ophidology (serpentology)

• It is study of snakes. (The study of lizards is Saurology)

Palaeontology

• It is the study of fossils which are preserved remains or the traces of
• organisms that lived in the past, and are now extinct.

Phylogeny

• It is study of evolutionary development, or racial history of a group

Physiology

• It is the study of functions of the body systems of animals and plant life,
• covering vital activities at cellular, tissue and organ level.

Pisciculture

• It is rearing and management of fishes at commercial level

Serology

• It is study of antigen-antibodies and serum

Splanchnology

• It is study of visceral organs (present beneath splanchnic mesoderm)

Systematics

• It is the study of diversity and evolutionary relationship of organism
• based on comparative study of different fields of biology.

Taxonomy

• It is a scientific study of principles and procedures of classification.

SCOPE OF BIOLOGY

• Food storage, cancer, population explosion, poverty, AIDS, and global warming are the burning issues related to human welfare.
• Study of medicinal plants has helped in the production of Quinine, Penicillin, Nux vomica, antibiotics etc. for serving the mankind.
• Study of classification, life history, vector and diseases has helped in combating human miseries.
• With the knowledge of genetics the hereditary diseases and genetic disorder are being minimized.
• A number of new courses or specialization, like – Horticulture, Jute technology, Fisheries, Tea Technology, Apiculture, Sericulture. Poultry farming, Aquaculture etc. have emerged. These can be useful in the development of national economy.
• Genetically modified (GM) crops are being developed to solve the problem of food shortage.
• Direction of bio-technology, conservation of bio-diversity, maintenance of environment and human welfare are in the hands of biologists. Biodiversity, including wild life, is immensely important for human existence.

MYTHS, DISBELIEFS OR MISCONCEPTIONS IN BIOLOGY AND THEIR REALITY

Myths/ Misconceptions	Reality/ Fact
Snakes can hypnotize or charm their prey	The prey becomes motionless, perhaps due to fear.
Snakes dance at the tune of the flute of snake charmer	They do not have external and middle ear to receive sound.
Snakes visit barns to suck the milk from the teats of cattle	Snakes are carnivores and visit barns for rats only.
Malaria (mal-bad, aria-air) is caused by foul air	Malaria is caused by the species of Plasmodium, and is transmitted by female Anopheles (mosquito).
AIDS spreads by sharing food, social kissing or caring	AIDS spreads by direct contact with body fluids.

MISUSE OF BIOLOGY

Amniocentesis

• Amniotic fluid contains foetal-skin cells and amniocytes of amniotic membrane. These cells are cultured for chromosomal study for detecting fetal abnormality. This technique is now being used for sex identification of Embryo / foetus (Between 1½ – 2 ½ months), and the fetus is aborted if found to be a female. It is the misuse of a biological technique

Bioweapons

• It is the development of antibiotic- resistant microorganisms. The spores of Anthrax bacteria (Bacillus anthracis) produced and stored to keep them viable for long have been used as a weapon of bioterrorism. The other similar diseases, on epidemic or endemic scale, can be plague and small-pox etc.

CAREERS IN BIOLOGY

1. Professional Courses

2. Vocational Courses

Professional Courses

Anthropology

• It is related to the study of physical, mental, cultural and social development of past and present man

Bioinformatics

• It is related to the application of computing systems and computational solution of techniques, analyzing data obtained by experiments, modeling, database searching and instrumentation to discover biological processes.

Biomedical Engineering

• It deals with the production of spare parts for human, like implants, artificial limbs, and machines for monitoring the health.

Biotechnology

• It is related to the creation, development and marketing of products through the willful manipulation of life forms on a molecular level.

Computational biology

• It is related to application, development and validation of computational hardware and software solutions for building simulation models of biological systems.

Computer Simulation

• It converts the physiological phenomena into graphical and multimedia presentation without actually involving organisms.

Dairy Technology

• It is related to the improved varieties of cattle, the extraction, preservation and marketing of the milk and milk-products.

Genetic Engineering

• It is related to the extraction of selected genes from an organism or synthesizing their copies and inserting them into another completely different organism.

Medical Transcription

• It is the course of Interpreting and typewriting (transcribing) dictation from physicians and other healthcare providers regarding patient assessment for diagnostic and therapeutic purposes.

Medicine

• It is the science of treating diseases with drugs or chemicals.

Occupational therapy

• It deals with the treatment of physically handicapped using physical exercises or vocational training

Pathology

• It deals with the diagnosis of pathogens and the diseases by analyzing the chemistry of the body fluid of the affected organisms.

Environmental Management

• It is about assessment of environment, environmental problems and the conservation of biodiversity for maintaining the balance in nature.

Surgery

• It is related to anatomy and physical operations to cure the patients suffering from diseases that cannot be cured with medicines.

Veterinary science

• It deals with the health, care and management of domestic animals

Vocational Courses

Agronomy

• It is the production and management of crops

Apiculture

• It is rearing and maintenance of bees for the production and marketing of honey and wax at the commercial level.

Breeding Biology

• It is for the improvement of varieties of plants or animals by selective breeding. (It does not manipulate genes).

Forensic Science

• It deals with the application of scientific knowledge, like finger prints, blood typing, and DNA analysis etc., to deal with criminal activities and laws.

Pharmacy

• It is related to the production and identification of drugs.

Pharmacology

• It is related to the nature, preparation, action and effects of medicines.

Pharmacognosy

• It is related to study of action of drugs.

Physiotherapy

• It is related to the treatment of defect, disease or weakness by physical remedy as exercises and massage. No drugs are administered in physiotherapy.

Poultry farming

• It is the rearing of breeds of poultry birds like domestic fowl, chicken, ducks for eggs and meat etc. at commercial level.

Prawn Farming

• It is rearing, transportation and marketing of prawns. It is a part of fisheries.

Sericulture

• It is related to the rearing of different strains of silkworms for the production, transportation and marketing of silk at commercial level.

Part-II : Taxonomy

More than 1.2 million animal species, and more than 0.5 million plant species have been identified and described so far

The purpose of biological classification is to name and remember the organisms.

Species

• It is the basic unit of classification. According to ‘Biological concept of species’, the species can be defined as a group of natural populations whose members can interbreed among themselves and are reproductively isolated from other such groups.

Types of species

Morphological/ Typological/ Taxonomic species and Biological species

• Taxonomic species are identified on the basis of morphological characters while biological species are identified on the basis of interbreeding. The term Biological species is not applicable for fossils or asexually reproducing organisms.

Static species and Non- static species

• Species in the beginning, i.e. before Lamarckism, were thought to be unchangeable so called static but after Lamarckism the species have been considered to be non- static or dynamic.

Monotypic species and Polytypic species

• Monotypic species are those which contain only one subspecies while polytypic species contain many subspecies.

Allochronic and Synchronic species

• Allochronic species belong to different time period where as the Synchronic species belong to same time period.

Allopatric and Sympatric species

• Allopatric species occur in different geographical areas while Sympatric species occur in the same geographical area.

Sibling species or cryptic species

• Two different species which are morphologically identical or indistinguishable but are reproductively isolated, e.g. Drosophila pseudobscura and D. persimilis.

IMPORTANT TEMS

Nomenclature

• It is the process of giving scientific names (not vernacular or local names) to the organisms.

Classification

• It is the process of grouping animals and plants into convenient categories on the basis of certain observable traits.

Identification

• It is determination of correct position of an organism in the classification.

Taxonomy

• It is the study of the process of classification.

Systematics

• This includes the identification, nomenclature and classification of organisms based on various parameters.

New-Systematics

• This covers systematic studies considering evolutionary relationship including other branches like Molecular biology, Cytology, Genetics and Biochemistry also etc.

History of Classification

Hippocrates – (460-377 BC)

• He classified animals into various groups like insects, fishes and birds etc.

Aristotle (384-322 BC)

• Wrote Historia animalium
• Father of zoology / biology
• He classified animals on the basis of red blood, into Anaima and Enaima. Anaima included animals without red blood. Enaima, with red blood, was further divided into ovipara and vivipara.

Theophrastus (370-285 BC)

• A Greek naturalist, and pupil of Aristotle
• Father of botany.
• He classified plants into Trees, Shrubs, Under- Shrubs and Herbs, and also described around 500 plants in his book Historia plantarum.

John Ray (1686)

• A British botanist
• He described 1800 plant and animal species in Historia Generalis Plantarum.
• He also Introduced the terms Species, Genus and Family

Carrolus Linnaeus

• A Swedish naturalist
• Father of taxonomy
• He coined the terms ‘Class’ and ‘Systematics’ (Term Taxonomy was given by A. P. De Condolle)
• He published Systema Naturae, Genera Plantarum and Species Plantarum (1753). In Species Plantarum he classified 4000 species of plants on the basis of sexual characters (Artificial system of classification)
• He proposed Linnaean Hierarchy with 5- taxa, i.e. Class, Order, Genus, Species and Varieties.
• Linnean’s principles of Binomial Nomenclature were given in Philosophia Botanica (1751) and finally in Species Plantarum (1753) for plants, and in 10th edition of Systema Naturae (1758), for animals. The Law of Priority for nomenclature is, therefore, applicable from year 1753 for plants, and from year 1758 for animals.

Rules of Nomenclature

1. In bionomial nomenclature each scientific name has 2- components,
2. Generic name (Genus),
3. Specific name/ epithet (Species)
4. The generic name begins with capital letter, whereas the specific name, with small letter.
5. Both the generic and specific names, are separately underlined (if hand written), or given in italic (if printed) to indicate their Latin origin. e.g., Amoeba proteus, Panthera tigris, Homo sapiens and Pavo cristatus
6. The first (generic) name is usually a noun, whereas the second (species) is an adjective.
7. The scientific name of the organism is generally followed by the name (full or abbreviated) of the person/ author, who first described the species. e.g., Homo sapiens Linnaeus 1758 However, if the species, after its first publication is transferred to any other genus, or the generic name is changed, the first author’s name is given in parenthesis (brackets); e.g., Panthera leo (Linnaeus). Mr. Linnaeus assigned the species, leo, in the genus Felis. If the specific name is given in the honour of a person, then this name ends in ‘i’, if the person is male, or, in ‘ae’, if the person honoured is female. e.g., Lumbricus friendi (after Mr. R H Friend)

Tautonym

• It is a binomial name in which the names of genus and species are the same. e.g. Gorilla gorilla

Trinomial nomenclature

• It includes Genus, Species and Subspecies, and is applicable to animals only.
• The botanists do not recognize subspecies level.

Turrill

• He introduced the terms α – taxonomy and β – taxonomy for Classical systematics and New systematics respectively.

Lamarck and Treviranus

• Introduced term ‘Biology’

Cuvier

• Father of modern Palaeontology
• He also introduced the term ‘Phylum’

Ernst Haeckel (1868)

• He suggested two new kingdoms, Monera and Protista

Julian Huxley

• Introduced the term ‘New- Systematics’

Ernst Mayr (1940)

• He proposed Biological concept of species, on the basis of interbreeding.

Copeland (1956)

• Suggested 4 – kingdoms – classification, i.e. Monera, Protista, Animalia and Plantae

Whittaker (1969)

• Introduced 5- kingdom classification, i.e. Monera, Protista, Animalia, Plantae and Fungi.

Carl Woese et al.

• They created 3-monophyletic Domains, above kingdom level, i.e. Archaea, Bacteria and Eukarya,
• Introduced 6- kingdom classification on the basis of ‘sequence of Ribosomal RNAgenes’.
• D. Archaea included kingdom Archaebacteria, D. Bacteria included kingdom Bacteria and D. Eukarya included 4 – kingdoms, ie. Protista, Animalia, Plantae and Fungi.

Basic categories of Taxonomic hierarchy

There are 7- basic categories of hierarchy

1. Kingdom
2. Phylum (in animals)/ Division (in plants)
3. Class
4. Order
5. Family
6. Genus
7. Species

However, there are other subcategories also, like subphylum, subclass, suborder, subfamily and subspecies. The category (taxon) ‘Cohort’ is used by palaentologists between class and order. Similarily, ‘Tribe’ has recently been introduced between subfamily and genus

Please Remember that

1. two generic names in any kingdom cannot be the same
2. all organisms, either in plant or animal-kingdom, have the Species as the lowest category.

The term ‘Taxon’ is used to refer to any rank or level or category of the classification. Hence, the Dogs, Carnivora, Mammals and Animals are all taxa at different levels of hierarchy. The term ‘taxon’ for animals was given by Adolf Meyer (1926).

Species – It is the lowest category in basic taxonomic hierarchy and has the maximum common characterstics with other species under the same genus. In genus Panthera, there are several species, like, tigris, pardus and leo etc.

Genus – The genus is an aggregate or a group of closely related species. The generic names of Panthera, Felis, Homo and Canis are common. The taxon Genus has more common characterstics with other genera than the higher ranks.

Family – It is the group of closely related genera, and has less common characterstics than species or genus rank. The cats and dogs belong to Felidae and Canidae families respectively. (The suffix used for family, subfamily and tribe in animals are –idae, –inae and –ini respectively.)

Order – It is a higher taxon and is the assemblage of families having similar characterstics. However, the common characterstics will be fewer than at family or genus level. In mammals the common order are Primates (monkey, gorilla and human), Carnivora, Rodentia and Cetacea (whale and dolphin)

Class – It is a group of related orders. The lizards, birds and cattle belong to class Reptilia, Aves and Mammalia respectively.

Phylum – The classes with similar features are grouped into Phylum in animals and Division in plants. The phylum share very few common characterstics with other phyla. The common characterstics of phylum Chordata are- Dorsal tubular nervous system, Notochord and the Pharyngeal gill slits at some stage of life cycle. Other phyla are Annelida, Arthropoda and Mollusca etc.

Kingdom – The phyla are grouped into still broader categories, called kingdom. You are familiar with animal kingdom and plant kingdom. Thus in above taxonomic hierarchy as we move from lower to higher (species to kingdom) rank, the number of common characterstics go on decreasing. Lower the taxon more are the common characterstics, and higher the taxon the fewer are the common features.

Taxonomic categories of common animals-

1. Kingdom
2. Phylum or Division
3. Class
4. Order
5. Family
6. Genus
7. Species

Concept of species

Typological species concept

• It is simpler and widely accepted concept
• All individuals of a species match the ‘type specimen’ very closely. The ‘type specimen’ used for the nomenclature in this system is called Holotype.
• The other type of specimen can be Paratype, Isotype and Lectotype etc. The Isotype is the copy of the Holotype. The Paratype is the one which is cited with the original description but is neither Holotype nor Isotype. The Lectotype is the specimen from original material, in the absence of Holotype.

Biological species concept

• It is based on interbreeding of the members.
• It is not applicable to fossils or asexually reproducing organisms, as they cannot interbreed

Types of Classification

Artificial system of Classification

• All taxonomists, from Aristotle to Linnaeus, classified organisms on the basis of external observable (morphological) characters like floral structure (Number of stamens), root modification, leaf venation etc.
• In this system no weightage was given to natural and Phylogenetic relationship. Such system is based on one or a few superficial similarities. This is an arbitrary system of classification.
• Linnaeus also used such system of classification. This system may also be based upon habit and habitats of the organisms.

Natural System of Classification

• It uses more number of characters and is based upon natural affinities using homology and comparative study.
• Bentham – Hooker used this system of classification for angiosperms.

Numerical Taxonomy ( Phenetics ) or Quantitative taxonomy

• This system uses numerical methods for evaluating the similarities and differences between the species.
• This uses maximum number of characters, without giving extra emphasis on anyone.
• Sophisticated calculating machines and computers are used for statistical analysis,. This system gives equal importance and weightage to all the characters used for taxonomy.
• As this system was first attempted by Adanson (1763), the numerical taxonomy is also known as Adansonian system (The Phenetics is considered to be a better classification as it uses a huge number of comparative features).

Phylogenetic Classification (Cladistics)

• This system of classification is based upon evolutionary relationship and uses morphological characters, origin and evolution of the different organisms. The ‘Family tree’ in this system is called Cladogram.
• This system has led to the emergence of new systematics and bio-systematics.
• Phylogenetic system of classification was proposed by Hutchinson.
• Adolf Engler and K. Prantl, both German Botanists, published ‘Phylogenetic system of classification’ in plants and considered monocots to be the more primitive than the dicot angiosperms. They published twenty volumes of classification (from algae to angiosperm) in Die Natuerlichen Phlanzenfamilien.

Karyotaxonomy

• This system of classification uses information like chromosome number, structure of chromosomes, size and shape of chromosomes and the behavior of chromosomes during meiosis.

Chemotaxonomy

• This system is based on chemical products, particularly secondary metabolites. Various families of plants have been identifi ed on the basis of raphides (Crystals of calcium oxalates)

Experimental taxonomy

• Here the relationship is determined on the basis of genetics, breeding experiments and the effect of captivity.

Bio-chemical taxonomy

• It is based on the bio-chemistry of various chemicals like hormones, pheromones etc.

The Population systematics and Biosystematics are the new branches of classification. The Biosystematics is the classification of organisms based on evolutionary history and phylogeny considering various parameters in totality, from all the fields of biology.

Codes of nomenclature

1. International code of Botanical nomenclature (ICBN)
2. International code of Zoological nomenclature (ICZN)
3. International code of Bacteriological nomenclature
4. International code of viral nomenclature (not based on binomial nomenclature)
5. International code of nomenclature for cultivated plants

The international code of Zoological nomenclature was adopted in 1964 and was published in two languages, i.e. English and French.

TAXONOMIC AIDS

• The taxonomic studies of animals, plants and microorganisms help is knowing our bio-resources and their diversity. The biologists have established certain procedures and techniques to store and preserve the information as well as the specimens. The following are the important taxonomic aids

1. Herbarium
2. Botanical gardens
3. Zoological parks
4. Biological Museums
5. Keys
6. Manuals
7. Flora
8. Monograph
9. Periodicals and catalogues

Herbarium

• It is the store house of dead, dried, pressed and preserved plant specimens on paper sheets, called herbarium sheets. The sheets, along with description of plant specimen, are arranged according to standard system of classification, and are stored for future use. All sheets carry labels having information about date and place of collection, English, local and botanical names, family and collector’s name etc. The herbarium sheets can be used as a quick reference for taxonomic studies.

Botanical gardens

• These gardens have a collection of living plants for identification and taxonomic studies. Each plant is labeled indicating its botanical or scientific name and its family. The famous Indian botanical gardens are –

1. Indian Botanical garden, Howrah;
2. National Botanical Research Institute, Lucknow, The world famous botanical garden is at Kew, England.

Zoological parks (Zoos)

• In such places the wild animals are kept in protected environment under human care. As far as possible, these animals are provided the conditions similar to their natural environment. Zoos help us to learn about the food habits and behaviour of the animals in captivity.

Biological Museums

• These have the collection of preserved animals and plants specimens for study and reference. Biological museums are generally set up in educational institutes, i.e. School and colleges. The specimens may be preserved dry or in preservative solution in jars or containers. The insects are preserved in insect boxes after collecting, killing and pinning. The larger animals, like mammals and birds are stuffed and are chemically treated for long term preservation. Museums also have collection of animal skeletons.

Keys

• The key is a device or scheme used for identification of animals and plants. The keys are generally analytic in nature. Separate taxonomic keys are required for separate taxa.
• Such keys are of 2- types

        (a) Indented key or Yoked key, (b) Bracketed key

1. Indented key – It provides sequence of choices between two or more characters. The user has to make the correct choice of statement or character for identification
2. Bracketed key – It has one pair of contrasting statements for identification. Each statement in the key is called a lead. The numbers given on the right hand side indicate the next choice of paired contrasting statements.

Example –Each set with 1-pair of Contrasting characters

Manuals

These taxonomic aids contain information for the identification of names of species found in an area, They also provide information about keys, description of family, genus and species.

Flora

It contains actual account of the habitat and distribution of plants of a given area, i.e., an index to the plant species found in a particular area.

Monograph (Memoir)

They are taxonomic aids that give comprehensive information on one family or genus at a given time

Periodicals and Catalogues

They provide information about new additions, and update the records. The catalogues are also the means for recording information for taxonomy.