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CBSE Quick Revision Notes (Class-11 Biology) CHAPTER-02 BIOLOGICAL CLASSIFICATION
Biological classification is the scientific procedure of arranging organisms into groups and subgroups on the basis of their similarities and dissimilarities and placing the group in a hierarchy of categories. Importance of classification-
- It is not possible to study every organism. Study of one or two organism of a group gives sufficient information about the essential features of the group.
- It helps in identification of new organism.
- Classification helps in knowing the relationship amongst different groups of organisms.
- The organism of past cannot be studied without a proper system of classification.
Artificial system of classification - One or two morphological characters for grouping of organism is used only. Flowering and non-flowering plants, enaima and anaima. Aristotle classification. Natural system of classification - Takes into consideration comparable study of a number of characters so as to bring out natural similarities and dissimilarities and hence natural relationships among the organisms. Bentham and Hooker classification etc. Phylogenetic System of Classification - Based on the evolutionary relationship of organisms. In this system organism are classified on the basis of their evolution on earth from primitive to highly evolved. Engler and Prantl classification and Hutchinson classification etc. Depending upon the type of system of classification organism are classified into following kingdom system.
Classification
Artificial system of Classification Natural system of Classification Phylogenetic system of Classification
Kingdom System of claasification
Two Kingdom Plantae Animalia
Three Kingdom Plantae Protista Animalia
Five Kingdom Monera Protista Fungi Plantae Animaila
In kingdom two system of classification organisms are grouped on the basis of presence and absence of cell wall as proposed by Linnaeus( father of taxonomy). Three kingdom systems- Haeckel separated unicellular animals, algae and fungi on the basis of lack of tissue differentiation and new kingdom Protista was introduced. Five kingdom systems- R.H.Whittaker divided all the organism into five kingdom in order to develop phylogenetic classification.
1. Monera - The kingdom includes all prokaryotes- mycoplasma, bacteria, actinomycetes and cyanobacteria. (a) Unicellular, prokaryotes and contain the most primitive of living forms (b) The cells are microscopic and cell wall is generally present. (c) Genetic materials are not organized into nucleus and contain naked DNA. (d) Membrane bounded organelles are absent. (e) Reproduction is asexual except gene recombination. (f) Flagella may be present and are of single stranded. Example- Blue-green algae, Bacteria etc. Bacteria are the most abundant micro-organism that can survive in all kinds of climate.
Archaeobacteria – They are group of most primitive prokaryotes which live under most hostile conditions like extreme salty area (halophiles), hot springs (thermoacidophiles) and marshy area (methanogens). They differ from other bacteria in having different call wall structure (absence of peptidoglycan). Methanogens are present in the gut of several ruminant animals like cows and buffalo, which is responsible for production of biogas (methane)from dug of these animals. Eubacteria – They are called as true bacteria contain rigid cell wall, if motile contain flagellum. Cyanobacteria or blue-green algae are gram positive photosynthetic bacteria. They contain chlorophyll a and carotenoids. They may be unicellular, colonial or filamentous, fresh water, marine or terrestrial. Some of them have specialized heterocyst cells to perform nitrogen fixation (Nostoc and Anabaena). Chemosynthetic bacteria oxidize inorganic substances like nitrate, nitrite, ammonia etc. to produce energy and help in recycling of nitrogen, phosphorous, sulphur etc.
Coccus Spherical shaped
Spirillum spiral or coiled shaped
Bacillus rod shaped
Vibrio comma shaped
Bacteria
Eugleoids They are Euglena like unicellular flagellates which possess pellicle instead of cell wall which make their body flexible. They have two flagella, one short and other long. They are photosynthetic in presence of sunlight and act as predators in absence of sunlight. Example- Euglena, Peranema. Slime Moulds They are saprophytic protists and feeds on decaying twinges and leaves. Under favorable condition, they form an aggregation called plasmodium which produce fruiting bodies bearing spores. The cell wall of spores bears cellulose. Example- Physarum, Fuligo. Protozoans All protozoans are heterotrophs and live as predators of parasites. They are considered as primitive relatives of animals. Amoeboids move and capture food by pseudopodia. Some are parasitic also. Flagellated protozoans are free-living or parasitic. They have flagella. Ciliated protozoans are aquatic and have cilia all over the body for movement. Sporozoans includes organism that have infectious spore like stage in their life cycle.
3. Fungi – They are achlorophyllous, heterotrophic, spore forming, non-vesicular eukaryotic organisms. Cell wall is made up of chitin or fungal cellulose. Reserved food is glycogen. Mode of nutrition is saprophytic, parasitic or symbiotic. Reproduction may be vegetative (fragmentation, fission or budding), asexual (conidia, sporangiospores or zoospores) or sexual reproduction by oospores, ascospore and basidiospores. Sexual cycles involves the following steps-
Protozoan
Amoeboids Amoeba, Entamoeba
Flagellated Trypanosoma
Ciliated paramoecium
Sporozoans Plasmodium
(a) Plasmogamy, fusion of male and female gametes. (b) Karyogamy, fusion of two nuclei. (c) Meiosis in zygote to produce haploid spores. (a) Phycomycetes -
- They are found in aquatic habitat and on decaying wood in moist and damp places.
- The mycelium is aseptate and coenocytic.
- Asexual reproduction by zoospores( motile) or aplanospores (non-motile).
- Example- Mucus, Rhizopus, Albugo et
(b) Ascomycetes (The sac fungi)
- They are saprophytic, decomposers, parasitic or coprophilous (growing on dung).
- Mycelium and branched and septate and asexual spores are conidia.
- Sexual spores are called ascospores produced inside the fruiting body called ascocarps. Example- Neurospora, Asperigillus, Claviceps etc. (c) Basidiomycetes ( The club fungi)
- The mycelium is branched and septate.
- Vegetative reproduction is by fragmentation. Asexual spores are not found. Sexual reproduction is by two vegetative or somatic cells forming basidium.
- Basidiospores are produced in basidium by developing a fruiting body called basidiocarps.
- Example- Agaricus, Ustilago, Puccinia. (d) Deuteromycetes ( The fungi imperfect)
- Only vegetative and asexual phase is known.
- Mycelium is septate and branched. Some members are saprophytes or parsites.
- Example- Alternaria, Trichoderma, Colletotrichu. 4. Plantae (a) Eukaryotic, chlorophyll bearing organism. (b) Life cycle is divided into diploid saprophytic and haploid gametophytic, which alternate with each other. (c) Kingdom Plantae includes Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms. 5. Animalia
Fungi
Ascomycetes
Phycomycetes
Deuteromycete s
Basidiomycetes
