Biological classification
- 2. Classification History The earliest classification was done by Aristotle. He used simple morphological characters to classify plant into trees, shrubs & herbs. He also divided animals into two groups, those who poses red blood and those who did not.
- 3. Classification HistoryLinnaeus classified living world into Two kingdom. Plantae and Animalia.This system was used till very recently. This system does not distinguish between Eukaryotic and prokaryotic ,unicellular and multicellular organisms and photosynthetic (green algae) and non-photosynthetic (fungi) organisms.
- 5. 5 Kingdom Classification R.H. Whittaker (1969) proposed a Five Kingdom Classification. The kingdoms defined by him were named Monera, protista, Fungi, Plantae and Animalia. The main criteria for classification used by him include cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships. .
- 6. All prokaryotic organisms were grouped together under Kingdom Monera and the unicellular eukaryotic organisms were placed in Kingdom protista. Kingdom Protista has brought together Chlamydomonas, Chlorella (earlier placed in Algae within Plants and both having cell walls) with Paramoecium and Amoeba (which were earlier placed in the animal kingdom which lack cell wall). It has put together organisms which, in earlier classifications, were placed in different kingdoms.
- 8. Kingdom Monera Bacteria mainly comprises of the Kingdom Monera. They are the most abundant micro-organisms. They live in extreme habitats such as hot springs, deserts, snow and deep oceans .Many of them live in or on other organisms as parasites. Bacteria are grouped under four categories based on their shape the spherical Coccus , the rod-shaped Bacillus , the comma shaped Vibrium and the spiral Spirillum Some of the bacteria are autotrophic, i.e., they synthesise their own food from inorganic substrates. They may be photosynthetic autotrophic or chemosynthetic autotrophic. The vast majority of bacteria are heterotrophs,i.e., they do not synthesise their own food but depend on other organisms or on dead organic matter for food. Back NextSlide 9
- 10. These bacteria are live in the most harsh habitats such as extreme salty areas (halophiles), hot springs (thermoacidophiles) and marshy areas (methanogens). Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is responsible for their survival in extreme conditions. Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane (biogas) from the dung of these animals. Archaebacteria Next
- 11. Eubacteria There are thousands of different eubacteria or ‘true bacteria’. They are characterised by the presence of a rigid cell wall, and if motile, a flagellum. Some of these organisms can fix atmospheric nitrogen in specialised cells called heterocysts, e.g., Nostoc and Anabaena. They play a great role in recycling nutrients like nitrogen, phosphorous, iron and sulphur. Heterotrophic bacteria are the most abundant in nature. The majority are important decomposers. Many of them have a significant impact on human affairs. They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots, etc. Some are pathogens causing damage to human beings, crops, farm animals and pets. Cholera, typhoid, tetanus, citrus canker are well known diseases caused by different bacteria. Bacteria Growth mainly by fission (Figure 2.3). Sometimes, under unfavourable conditions, they produce spores. They also reproduce by a sort of sexual reproduction by adopting a primitive type of DNA transfer from one bacterium to the other. Next
- 12. The Mycoplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasma are pathogenic in animals and plants. Dividing Bacterium Back
- 13. Kingdom Protista All single-celled eukaryotes are placed under ProtistaMembers of Protista are primarily aquatic. This kingdom forms a link with the others dealing with plants, animals and fungi. Being eukaryotes, the protistan cell body contains a well defined nucleus and other membrane-bound organelles. Protists reproduce asexually and sexually by a process involving cell fusion and zygote formation. Next
- 14. Protista Chrysophytes Dinoflagellates Protozoans Slime Moulds Eugelenoids Next
- 15. Chrysophytes This group includes diatoms and golden algae (desmids). They are found in fresh water as well as in marine environments. They are microscopic and float passively in water currents (plankton). Most of t hem are photosynthetic. Triceratium Pinnularia Next
- 16. Dinoflagellates These organisms are mostly marine and photosynthetic.They appear yellow, green, brown, blue or red depending on the main pigments present in their cells. The cell wall has stiff cellulose plates on the outer surface. Most of them have two flagella. Very often, red dinoflagellates(Example: Gonyaulax) undergo such rapid multiplicationthat they make the sea appear red (red tides). Toxins released by such large numbers may even kill other marine animals such as fishes. Red Tides Next
- 17. Eugelenoids Eugelenoids are fresh water organisms found in stagnant water. Instead of a cell wall, they have a protein rich layer called pellicle which makes their body flexible. Though they are photosynthetic in the presence of sunlight, when deprived of sunlight they behave like heterotrophs by predating on other smaller organisms. Interestingly, the pigments of euglenoids are identical to those present in higher plants. Example: Euglena Next
- 18. Slime Moulds Slime moulds are saprophytic protists. The body moves along decaying twigs and leaves engulfing organic material.Eg.plasmodium. Plasmodium Next
- 19. Protozoans All protozoans are heterotrophs and live as predators or parasites. They are believed to be primitive relatives of animals. There are four major groups of protozoans. Next
- 20. Types of Protozoans:- Amoeboid Protozoans: These organisms live in fresh water, sea water or moist soil. They move and capture their prey by putting out pseudopodia (false feet) as in Amoeba. Some of them such as Entamoeba are parasites. Flagellated Protozoans: The members of this group are either free-living or parasitic. They have flagella. The parasitic forms cause diseases such as sleeping sickness. Example: Trypanosome. Amoeba Trypanosome Next
- 21. Types of Protozoans:- Ciliated protozoans: These are aquatic, actively moving organisms because of the presence of thousands of cilia. They have a cavity (gullet) that opens to the outside of the cell surface. Example: Paramoecium Sporozoans: This includes diverse organisms that have an infectious spore-like stage in their life cycle. The most notorious is Plasmodium (malarial parasite) which causes malaria which has a staggering effect on human population Paramoecium Exit
- 22. Kingdom Fungi The fungi constitute a unique kingdom of heterotrophic organisms. They show a great diversity in morphology and habitat. Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes. Those that depend on living plants and animals are called parasites. They can also live as symbionts – in association with algae as lichens and with roots of higher plants as mycorrhiza.Reproduction in fungi can take place by vegetative means – fragmentation, fission and budding. Asexual reproduction is by spores called conidia or sporangiospores or zoospores, and sexual reproduction is by oospores, ascospores and basidiospores. Next
- 24. Phycomycetes Members of phycomycetes are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plants. The mycelium is aseptate and coenocytic. Asexual reproduction takes place by zoospores (motile) or by aplanospores (non-motile). Some common examples are Mucor Rhizopus (the bread mould mentioned earlier) and Albugo (the parasitic fungi on mustard). Mucor Next
- 25. Ascomycetes Commonly known as sac- fungi, the ascomycetes are mostly multicellular, e.g., Penicillium rarely, or unicellular, e.g., yeast (Saccharomyces) . They are saprophytic, decomposers, parasitic or coprophilous (growing on dung). Mycelium is branched and septate Penicillium Next
- 26. Basidiomycetes Commonly known forms of basidiomycetes are mushrooms, bracket fungi or puffballs. They grow in soil, on logs and tree stumps and In living plant bodies as parasites, e.g., rusts and smuts. The mycelium is branched and septate. Some common members are Agaricus (mushroom) , Ustilago (smut) and Puccinia (rust fungus). Agaricus Puccinia Next
- 27. Deuromycetes Commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known. When the sexual forms of these fungi were discovered they were moved into classes they rightly belong to. Some members are saprophytes or parasites while a large number of them are decomposers of litter and help in mineral cycling. Some examples are Alternaria, Colletotrichum and Trichoderma. Exit
- 28. Lichens Lichens are symbiotic associations i.e. mutually useful associations, between algae and fungi. The algal component is known as phycobiont and fungal component as mycobiont, which are autotrophic and heterotrophic, respectively. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner. So close is their association that if one saw a lichen in nature one would never imagine that they had two different organisms withinthem. Lichens are very good pollution indicators – they do not grow in polluted areas. Lichens
- 29. Kingdom Plantae Kingdom Plantae includes all eukaryotic chlorophyll-containing organisms commonly called plants. A few members are partially heterotrophic such as the Insectivorous plants or parasites. The plant cells have an eukaryotic structure with prominent chloroplasts and cell wall mainly made of cellulose. Plantae includes algae, bryophytes, pteridophytes, gymnosperms and angiosperms Exit
- 30. Kingdom Animalia This kingdom is characterised by heterotrophic eukaryotic organisms that are multicellular and their cells lack cell walls. They directly or indirectly depend on plants for food. They digest their food in an internal cavity and store food reserves as glycogen or fat. Most of them are capable of locomotion. Exit
- 31. Virus & Viroids In the five kingdom classification of Whittaker there is no mention of some cellular organisms like viruses and viroids.The viruses are non-cellular organisms that are characterised by having an inert crystalline structure outside the living cell. Once they infect a cell they take over the machinery of the host cell to replicate themselves, killing the host. The name virus that means venom or poisonous fluid was given by Pasteur. D.J. Ivanowsky (1892) . viruses also contain genetic material, that could be either RNA or DNA. No virus contains both RNA and DNA. A virus is a nucleoprotein and the genetic material is infectious. Viruses cause diseases like mumps, small pox, herpes and influenza. AIDS in humans is also caused by a virus. In plants, the symptoms can be mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth. Tobacco mosaic virus
- 32. • Viroids: In 1971 T.O. Diener discovered a new infectious agent that was smaller than viruses and caused potato spindle tuber disease. It was found to be a free RNA; it lacked the protein coat that is found in viruses, hence the name viroid. The RNA of the viroid was of low molecular weight. Bacteriophage T.O. Diener