Taxonomy: Classification of Organism

  • Taxonomy is a system for naming and organizing things, especially plants and animals, into groups that share similar qualities.
  • Carl (Carolus) Linnaeus (1707-1778) was a Swedish botanist, physician and zoologist who formalized binomial nomenclature-the modern system of naming organism. He is known as the ‘father of modern taxonomy’.
  • Several scientists have classified the living organisms into different groups but at modern time the classification given by Whittaker (1969) is widely adopted in the world. He classified the organisms into five kingdoms viz²Monera, Protista, Fungi, Plantae and Animalia.

Kingdom Monera :

  • Kingdom Monera includes organisms that are single celled. The microorganisms are considered as the most ancient living forms on the earth. All the organisms of this kingdom are prokaryotes. These cells do not have nuclear membrane. The kingdom Monera includes bacteria, cyanobacteria and mycoplasma. They do not have specific mode of nutrition. They can be either aerobic or anaerobic. These organisms have rigid cell wall which is made up of peptidoglycan. Cell organelles like endoplasmic reticulum, mitochondria are absent. Reproduction is by spore formation or binary fission.
  • Mycoplasma are known to be the smallest living cells. They completely lack cell wall. This characteristic makes them naturally resistant to many common antibiotics such as peniciline or other beta-lactum antibiotics that target cell wall synthesis. They can survive without oxygen. Most of the mycoplasma are pathogenic in animal and plants e.g.
    M. pnuemoniae causes atypical pneumonia in humans.
  • Cyanobacteria are photosynthetic, that is, they can synthesize their own food. They are the photosynthetic prokaryotes able to produce oxygen. Cyanobacteria are also called ‘blue-green algae’, though the term algae in modern usage is restricted to eukaryotes. They can be found in almost every terrestrial and aquatic habitat. Cynobacteria such as Anabaena (a symbiont of the aquatic fern Azolla) can provide rice plantation with biofertilizer.
  • Bacteria are microscopic, single celled primitive organisms. Generally these are about 2 to 4 micron in length. They can live within soil, in the ocean and inside the human gut. Human relationship with bacteria is complex. Sometimes they lend a helping hand by curding milk into yogurt or helping with our digestion. At other times they are destructive, causing diseases like cholera,
    syphilis, leprosy, tuberculosis and MRSA (Methicillinresistant Staphylococcus aureus – a type of staph bacterial infection that is hard to treat because it cannot be killed by many common antibiotics).
  • On the basis of their nutrition, bacteria have been classif ed into heterotrophic and autotrophic bacteria.
  • Autotrophic bacteria are of two types ² (i) Photosynthetic and (ii) Chemosynthetic.
  • Archaebacteria belong to the domain Archaea and are single celled organisms that tend to live in extreme environments, like hot springs or high salt regions. In fact, these organisms boldly grow there, where others can not. They have been called Extremophiles, which means lover of extremes. Example- Methanogens are microorganisms that produce methane as a metabolic by product in hypoxic condition. They are common in wetland, where they are responsible for marsh gas and in the digestive tract of animals such as ruminants and human, where they are responsible for the methane content of belching (emit wind noisily from the stomach through the mouth) in ruminants and f atulence accumulation of gas in alimentary canal in humans. These microorganisms are similar to bacteria in size and simplicity of structure but radically different in molecular organization. They are now believed to constitute an ancient intermediate group between the bacteria and eukaryotes. They are also called archaea.
  • Rhizobia are diazotrophic bacteria that f x nitrogen after becoming established inside the root nodules of legumes. Rhizobia are unique in that they are the only nitrogen fixing bacteria living in a symbiotic relationship with legumes.
  • Unicellular organisms reproduce generally by asexual means. Asexual modes of reproduction includes binary fission, multiple fission, fragmentation, budding etc.

Kingdom Protista :

  • All single celled eukaryotes are placed under Protista. They are organisms which are unicellular or unicellular – colonial and which form no tissues. Protista kingdom includes chrysophytes (diatoms and golden algae), dinofagellates, euglenox, slime moulds and protozoas such as amoeba, paramecium, flagellata, ciliophora etc. Some protists reproduce sexually using gametes, while others reproduce asexually by binary fission.
  • Protists live in water, in moist terrestrial habitats, and as parasites and other symbionts in the bodies of multicellular
    eukaryotes. Protists are almost certainly polyphyletic and they do not have an exclusive common ancestor.
  • Some protists are significant parasite pathogens of animals (e.g. Plasmodium causes malaria in humans) and plants (e.g. Phytophthora infestans causes late blight in potatoes). Protist pathogens share many metabolic pathways with their eukaryotic hosts, which makes therapeutic target development extremely dif cult – a drug that harms a protist parasite is also likely to harm its host.

Kingdom Fungi :

  • Fungi is the plural word for fungus. Fungi are eukaryotic organisms. The study of fungi is called Mycology. Fungi lack chlorophyll and vascular bundle. Fungi are heterotrophs; they aquire food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment. Fungi reproduce both sexually and asexually.
  • Yeasts, molds, mushrooms are the example of fungi.
  • Yeast belongs to the division Ascomycetes of the kingdom Fungi. Most yeasts reproduce asexually by mitosis, and many do so by the asymmetric division process known as budding.
  • Mold or mould grows in the form of multicellular f lament called hyphae. In contrast, yeasts adopt a single-cell growth habit. Molds cause biodegradation of natural materials, which can be unwanted when it becomes food spoilage or damage to furniture etc.
  • Mushrooms belongs to the division Basidiomycetes of the kingdom fungi. They are fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. Mushrooms are used extensively in cooking, however, many mushroom species (e.g. Amanita phalloides which is called death mushroom) can be toxic.
  • Dimorphic fungi are fungi that can exist in the form of both mold and yeast (e.g. Penicillium marneffei, a human pathogen that grows as a mold at room temperature and as a yeast at human body temperature).
  • A mycorrhiza is a symbiotic association between a fungus and a plant.
  • A lichen is a composite organism that arises from the algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.

Kingdom Plantae :

  • These living organisms are made of eukaryotic cells and are multicellular. The cells have a cell wall which is made of cellulose. These are autotrophic and synthesize food by photosynthesis due to the presence of chloroplasts. They are divided into following divisions – Algae, Bryophyta, Pteridophyta, Gymnosperm and Angiosperm.
  • Pitcher Plant (Nepenthes) : This plant is able to synthesize its own food. This plant is insectivorous. Pitcher plant grows in soil which lacks in nitrogen. To meet the defeciency of nitrogen, pitcher plant traps the insects.
  • Xerophytic plants : A xerophyte is a species of plant that has adaptations to survive in an environment with little liquid water, such as desert or an ice or snow covered region. Popular examples of xerophytes are cacti, calotropis, aloe, pineapple and some gymnosperm plants.
  • Adaptations of xerophytes include reduced permeability of the epidermal layer, stomata and cuticle to maintain optimal amount of water in the tissues by reducing transpiration, adaptations of the root system to acquire water from deep underground sources or directly from humid atmosphere and succulence, or storage of water in swollen stems, leaves or root tissues. Their leaves are modified into spines.
  • Phreatophyte is a deep rooted plant that obtains significant portion of water that it needs from phreatic zone (zone of saturation) or the capillary fringe above the phreatic zone. The roots of such plants are approximately 25 to 30 meters reaching to underground water.
  • Hydrophytes : Hydrophytes are also referred as aquatic plants or macrophytes. These plants require special adaptations for living submerged in water or at the water’s surface. The most common adaptation is aerenchyma.
  • Halophytes : A halophyte is a salt-tolerant plant that grows in waters and soils of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangroove swamps, marshes and sloughs and seashores.
  • Epiphytes : Epiphyte is a plant that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it (Example – Orchids).
  • A flower sometimes known as a bloom or blossom, is the reproductive organ found in flowering plants. The biological function of flower is to effect reproduction, usually by providing a mechanism for the union of male gamete with female gamete. Flowers may facilitate outcrossing or allow self ng.
  • Ginger, potato, Garlic and Suran (jimikand) are the examples of rhizome, tuber, bulb and corm respectively.
  • Shakarkand (Sweet-potato) belongs to the family Convolvulaceae. Its edible part is root.
  • Sugarcane, potato and ginger are the modified stems. It means their food storage organ are stem.
  • In shaljam (Turnip), carrot and sweet potato, storage organ are the modified roots.
  • Pea is a dicotyledonous annual herbaceous plant. Tendril is present to support the plant. It belongs to Leguminosae family.
  • Sugarcane (Saccharum officinarum) belongs to the family Graminae or Poaceae. Generally stem cutting is used for its vegetative propagation. It has nodes and internodes.
  • Cloves are the aromatic flower buds of a tree in the family Myrtaceae Syzygium aromaticum, native of Indonesia and commonly used as spice.
  • Cloves health benefits include improving digestion, fighting bacteria, protecting the liver, fighting lung cancer, regulating blood sugar and relieving tooth pain.
  • Saffron : Saffron is a spice derived from the flower of Crocus sativus (family – Iridaceae). The vivid crimson stigmata and styles, called threads, are collected and dried to be used mainly as a seasoning and colouring agent in food. It has long been the world’s most costly spice by weight. In saffron safranol and picocrocin chemicals are found.
  • Okra (Ladies’ finger) : It is a flowering plant. It is valued for its edible green seed pods. Its pod is known as capsule. Its botanical name is Abelmoschus esculentus.
  • Turmeric (Curcuma longa) is a flowering plant of ginger family-Zingiberaceae. The modified shoot (stem) rhizome is edible part of it. Turmeric contains curcumin, a substance with powerful anti-inflammatory and antioxidant properties.
  • Sorosis : This type of fruit is found in Mulberry, Pineapple and Jack fruit. These fruits are derived from catkin, spike and spadix type of inflorescence.
  • Nut : A nut is a fruit composed of an inedible hard shell and a seed, which is generally edible. The fruits of Cashew nut and Trapa (Singhara) are examples of nut. The edible part of Singhara is seed.
  • Lychee : It is the sole member of the genus Litchi in the soapberry family, Sapindaceae. Fleshy aril of lychee is the edible part. It is a drupe (like a plum, a cherry or a mango), externally covered by a pink-red rough textured rind, easily removable.
  • Pome : A fruit consisting of a fleshy enlarged receptacle and a tough core containing the seeds, e.g. an apple or pear.
  • Pepo : Fruits having a fleshy, many-seeded interior and a hard or firm rind. The fruits of melon, squash and cucumber are called pepo.
  • Quinine is a medicine which is used to cure malaria. It is derived from the bark of cinchona tree which belongs to the family Rubiaceae. This plant is evergreen shrub or tree.
  • Arteether is a potent antimalaria drug derived from artemisinin, a sesquiterpene lactone isolated from Artemisia annua. This medicine is used in severe malarial condition when other medicine are unef ective to control malaria.
  • Chloroquine, primaquine, atovaquone are some other medicines used to treat malaria.
  • Retting is a process, employing the action of microorganisms, and moisture on plants to dissolve or rot away
    much of the cellular tissues and pectins surrounding bastfibre bundles, and so facilitating separation of fibre from the stem of sunn, hemp and jute.
  • Cotton is a soft, f uf y staple f bre that grows in a boll, or protective case, around the seeds of the cotton plants (Gossypium Malvaceae). Chemical composition of cotton is as follows – Cellulose – 91%, Water – 7.85%, Protoplasm 0.55%; Fats – 0.40%, and Minerals – 0.20%.
  • The botanical name of papaya is Carica papaya (family Caricaceae). Enzyme papain found in papaya which helps in digestion of protein. Papaya are yellow due to presence of xanthophyll pigments i.e. caricaxanthin present in the plastid of the fruit pulp.
  • Red apples get their colour from anthocyanin pigment.
  • The pigments found in some other edible parts of plants are – carotene in carrot, lycopene in tomato, xanthophyll in turmeric and betanin in Beta vulgaris (chukandar).
  • Opium is the dried latex obtained from the opium poppy (Papaver somniferum). Approximately 12% of the opium latex is made up of the analgesic alkaloid morphine, which is processed chemically to produce heroin and other synthetic opioids for medicinal use and for illegal drug trade. The latex also contains the closely related opiates codeine and thebaine, and non analgesic alkaloids such as papaverine and noscapine. The morphine is obtained from the unriped fruits of the plant.
  • The distinctive smell of garlic and onion is due to the presence of sulphur containing chemicals.
  • Some compounds in onions, garlic or both, can be responsible for bad breath and even body odour. These include-
  • Allicin- When the insides of a garlic bulb are exposed to air, a substance called alliin turns into allicin, which then changes into several sulphur containing compounds that gives garlic its smell.
  • Allyl methyl sulphide- This compound is released from both garlic and onion, when they are cut. Once eaten, the substance is absorbed into blood stream, and emitted through the lungs and skin pores.
  • Cysteine sulfoxide- This sulphuric compound in garlic and onions causes an unpleasant odour on the breath almost immediately after the vegetables are eaten.
  • Garlic and onions add f avour to meals and can provide health benef ts. Unfortunately, both can also cause bad breath, known as halitosis, especially when eaten raw.
  • Sulfenic Acid found in onion irritates lacrymal glands and produces tears in eyes.
    • Producers : Producers are autotrophic, make their food by taking sunlight and using the energy to make sugar. The green plants are producers.
    • Consumers : Consumers have to feed on producers or
      other consumers. Consumers are heterotrophs.
    • Herbivores : Herbivorous animals are primary
    • Carnivores : Secondary consumers which feed on
      herbivores (primary consumers).
    • Decomposer : Decomposers are the garbagemen of
      animal kingdom, they take all the dead animals and plants
      and break them down into their nutrient components so
      that plants can use them to make more food. These are
  • Capsaicin is responsible for sharp taste in chili peppers. Its chemical formula is C18H27NO3 . When it comes in contact with skin or mucous membranes it produces a burning sensation. The amount of capsaicin in a specific species of peppers is measured using the Scoville scale.
  • In botany, a bud is an undeveloped or embryonic shoot normally occurs in the axil of a leaf and stem or at the tip of stem. Once formed, a bud may remain for sometime in dormant condition or it may form shoot immediately. The term bud is also used in Zoology, where it refers to an outgrowth from the body which can develop into a new individual.
  • Cork is obtained from the bark of oak which botanical name is Quercus suber. Its native land is mediterranean region.

Kingdom Animalia :

  • Animalia kingdom includes all invertebrates and vertebrates animals. They are multicellular eukaryotic organisms.
  • With few exceptions, animals consume organic material, breathe oxgyen, are able to move and can reproduce sexually.
  • Over 1.5 million living animal species have been described – of which around 1 million are insects – but it has been estimated there are over 7 million animal species in total.
  • Arthropoda is the largest phylum in animal kingdom. It includes species in all habitats which constitute 60% of all known species of animals.
  • Crabs belong to the class Malacostraca (PhylumArthropoda).
  • Class Arachnida (Phylum-Arthropoda) are characterized by having two body regions, a cephalothorox and an abdomen. They also have 6 pairs of appendages : 4 pairs of legs and 2 pairs of mouth part appendages, the first pair of mouth part appendages is called chelecerae and second pair is called pedipalps. Examples : Scorpions, Spiders.
  • The ticks and mites belong to the order Araneae of class Arachnida. Their appendages are jointed, body is bisymmetrical and triploblastic.
  • Class Insecta (Phylum-Arthropoda) encompasses all insects. Insects have three main body segments, the head, thorax and abdomen. They have 3 pairs of legs.
  • The glowworm Arachnocampa luminosa (insect) is famous for having blue-green light on the end of its tail. Both adult and larva produce it in a process called bioluminescence. The glow is due to presence of an enzyme luciferase.
  • In female mosquitoes, all mouth parts are elongated. The labium encloses all other mouth parts like a sheath. The labrum forms the main feeding tube, through which blood is sucked. Paired mandibles and maxillae are present, together forming the stylet, which is used to pierce an animal’s skin. Thus the female mouth parts are adopted to suck and pierce.
  • Male mosquitoes mouth is adopted to suck the nectar of flowers.
  • The trachea is the respiratory organs and the malpighian tubules are excretory and osmoregulatory organs of the insects.
  • Echinoderm is the common name given to any member of the phylum Echinodermata (hard, spiny covering or skin) of marine animals. The adults are recognisable by their (usually five points) radial symmetry and include such well known animals as starfish, sea urchins, sand dollars, sea cucumbers, sea lilies etc. Echinoderms are second largest grouping of deuterostomes (a superphylum) after the chordates.
  • Echinoderms are generally oviparous but some of them are viviparous.
  • Octopus is a soft bodied, eight armed mollusc of the Phylum Mollusca class Cephalopoda. It is also known as Devilfish.
  • Giant squids (Architeuthis dux) and colossal squid (Mesonychoteuthis hamiltoni) are the largest invertebrates. The length of colossal squids is less but weight is more than giant squids.
  • Homeothermic or warm blooded animal species maintain a stable body temperature by regulating metabolic processes. The only known living homeotherms are birds and mammals (Their body temperature remains the same when it’s cold or hot outside).
  • Heterothermic or cold blooded animals, like reptiles, amphibians and fish become hotter and cooler, depending on the temperature outside (Their body temperature depends on whether it’s cold or hot outside).
  • Nocturnal animals can hunt, mate or generally active after dark. They have highly developed sense of hearing, smell and specially adapted eyesight. Examples of nocturnal animals are mosquito, bat, owl and kiwi. The aye-aye
    (Daubentonia medagascariensis), a type of lemur, is the world’s largest nocturnal primate. It uses echolocation to find its prey–the only primate known to do so.
  • Some animals name resemble with fish but they are actually not fishese.g. Jellyfish (Cnidaria); Starfish (Echinodermeta); Silverfish (Insecta) Cuttlefish (Mollusca); Hagfish (Cyclostomata); Devilfish (Mollusca) and Crayfish (Arthropoda) etc.
  • The some true fishes are flying fish, catfish, pipe fish, paddle fish, gold fish, globe fish, dogfish etc.
  • Scoliodon is also known as dogfish. It is a cartilaginous
  • Seahorse (Hippocampus) is a bony f sh.
  • Most fish exchange gases like oxygen and carbon dioxide using gills that are protected under the gill covers on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called f laments.
  • During winter ice forms on top of the water. Beneath the layer of ice there are layers of water where the temperature is more than 0o C. This is why the fishes live.
  • Amphibians (class-Amphibia) are any member of the group of vertebrate animals characterized by their ability to exploid both aquatic and terrestrial habitats. The name amphibian, derived from the ancient Greek term ‘amphibious’ which means ‘both kinds of life’.
  • Reptiles are tetrapod animals in the class Reptilia, comprising today’s turtles, crocodiles, snakes, amphisbaenians, lizards and their extinct relatives.
  • The king cobra (Ophiophagus hannah) is a venomous snake species in the family Elapidae, endemic to forests from India through South-East Asia. It is threatened by habitat destruction and has been listed Vulnerable on the IUCN Red List since 2010. It is the world longest venomous snake. Adult king cobras are 3.18 to 4 meters long. The female king cobra lays eggs (20 to 50 eggs) in the nest (Oviparous). Parental care is found in this snake i.e. guards its own nest till the emerging of of springs from the eggs.

Non-poisonous and poisonous snakes

  • Most snakes are non-poisonous but some snakes as krait, cobra and viper are poisonous snake.
  • Fangs are sharp, long, hollow or grooved teeth that are connected to a small sac in the snake’s head behind its eyes. These sacs produce a poisonous liquid called venom. For some snakes with really long fangs, the fangs will fold back into the mouth so they do not bite themselves.
  • Snake venom may contain twenty or more toxins.
  • The cobra and krait venoms are neurotoxic and cardiotoxic while the venom of viper is vasculotoxic and haemotoxic.
  • The poison gland of snakes are homologous to the salivary glands of vertebrates.
  • Bats are mammals of the order Chiroptera, with their forelimbs adopted as wings, they are the only mammals naturally capable of true and sustained fight. Bats are more manoeuvrable than birds, flying with their very long spread-out digits covered with a thin membrane or patagium.
  • The smallest bat (arguably the smallest extant mammal) is Kitti’s hog-nosed bat (bumblebee bat), which is 29-34 min length and 15 cm across the wings. The largest bats are the flying foxes (fruit bat) and the giant golden-crowned flying fox, which have a wingspan of 1.7 metre.
  • The blue whale (Balaenoptera musculus) is a marine mammal measuring upto 33 metre in length and with a maximum recorded weight of more than 180 metric tonnes. It is the largest animal known to have ever existed. Its lifespan is 80-90 years.
  • Sperm Whale (Physeter macrocephalus) is the largest of the toothed whales measuring about 55 feet and weight about 35 to 45 tonnes. It is carnivorous.
  • Sea Lion, Seal, Phoca, Walrus and Dolphins are aquatic mammals. Dolphin belongs to the order Cetacea while  other belong to the order Carnivora.
  • Dolphin is very intelligent animal.
  • River Ganga Dolphin is the National Aquatic Animal of India. Its scientific name is Platanista gangetica.
  • Sea cow is a giant herbivorous aquatic mammal.
  • Echdina and Platypuss are egg-laying mammals.
  • Nilgai (Boselaphus tragocamelus) is the largest Asian antelope (It is not a cow). It is one of the most commonly seen wild animals of central and northern India, often seen in farmlands or scrub forests.
  • Apes (super family-Hominoidea) are tailless primate of families Hylobatidae (gibbons-small ape) and Hominidae (chimpanzees, bonobos, orangutans, gorillas and human beings – great apes).
  • Human beings are categorized zoologically as member of broader ape superfamily, they are usually placed within their own subcategories on account of their larger brain size, more advanced cognitive abilities (particularly the ability to speak) and striding two legged gait.
  • The capacity of an adult human cranial cavity is 1200 – 1700 cm3