Ch 2. Biological Classification And The Important Topics
Introduction:
- Aristotle classified organisms for the first time.
- Two kingdom system includes – Plantae &Animalia.
Demerits of Two Kingdom system
- No difference in Eukaryotes and Prokaryotes.
- Heterotrophic Fungi kept in Plantae.
- Five kingdom system is given by R.H Whittaker (1969) viz. Monera, Protista, Fungi, Plantae and Animalia.
Kingdom Monera –
- Prokaryotic unicellular organisms.
- Most abundant.
- Also live in extreme habitats viz. Hotsprings, Snow etc. as endoparasite etc.
- eg. Bacteria.
- Some bacteria are autotrophic others are heterotrophic.
Archaebacteria –
- Cellwall different from other bacteria.
- Live in most harsh habitats eg. Halophile.
- Methanogens are found in the gut of ruminants and produce methane (CH4) gas.
Eubacteria –
- True bacteria.
- Rigid cellwall with or without flagellum.
- Cyanobacteria( Blue green algae) are also included in this group.
- Cyanobacteria are Photosynthetic autotrophs, unicellular, colonial or filamentous, with gelatinous sheath.
- Have Heterocyst for N2fixation eg. Nostoc, Anabaena, Oscillatoria, Rivularia, Gloeotrichia etc.
- Reproduction occurs by fission. Also by primitive type of sexual reproduction, by transferring DNA piece from one bacterial cell(+ strain) to other (- strain) (called cell Transduction)
Mycoplasma –
- Smallest unicellular anaerobic organisms having no cellwall.
- Pathogenic in plants and animals.
Kingdom Protista –
- Unicellular eukaryotes.
- Primarily aquatic.
- Some have cilia and flagella.
- Reproduction sexual and asexual both.
Crysophytes –
- Fresh water or marine microscopic Planktons.
- Mostly photosynthetic and cheif producer in ocean eg. Diatomsand Golden algae (Desmids).
- Diatoms with cellwalls in two halves having Silica (indistructible).
- Diatomaceous earth is formed by cellwall deposits of Diatoms and used in polishing, filtration of oils and syrups, fire bricks and explosives.
Dinofagellates –
- Marine.
- Photosynthetic yellow , green, blue, brown or red in colour.
- One longitudinal and other transverse two flagella.
- Gonyaulax causes Red tides.
Euglenoids –
- Fresh water forms.
- No cellwall, outer most layer pellicle.
- Two unequal flagella.
- Photosynthetic but also heterotrophic in absence of light ( Mixotroph).
Slime moulds –
- Saprophytes.
- Body is an aggregation called ‘Plasmodium’( multinucleate, without cellwall, irregular in shape and can spreadover several feet ).
- Plasmodium produces fruiting body having spores with walls which are highly resistant and spread through wind.
Protozoans –
- Fresh water or marine unicellular heterotrophs.
- Primitive relative of animals.
(a) Amoeboid Protozoans –
- Free living or parasites.
- Pseudopodia (false feet) formed eg. Amoeba ,Entamoeba.
(b) Flagellated Protozoans –
- Free living or Parasitic with flagella eg.Trypanosoma( causessleeping sickness).
(c) Ciliated Protozoans –
- With cilia eg. Paramecium(sleeper animalcule).
(d)Sporozoans –
- Spore like stage in life eg. Plasmodium vivax.
Kingdom Fungi –
- Fungi are a group of achlorophyllous, heterotrophic organisms with cell wall without cellulose.
- Saprophyte or Parasite or Symbiotic.
- Useful and Harmful both.
- Prefer to grow in warm and humid places.
- Unicellular (eg. Yeast) to multicellular filamentous body calledmycelium.
- One unit of mycelium called hypha .
- Mycelia maybe coenocytic (no septum) or septate.
- Lichens – Symbiotic association of fungus and algae.
- Mycorrhiza – Symbiotic association of fungi with root of higher plants eg. Pinus.
- Reproduction –Vegetative : by fragmentation and by spores.Sexual: by gametes.
- Three steps in sexual reproduction
1) Plasmogamy – fusion of protoplasm.
2) Karyogamy – fusion of nuclei.
3) Meiosis of zygote.
Phycomycetes –
- Grow on aquatic places or decaying wood or damp places or obligate parasite.
- Mycelium aseptate, coenocytic.- Reproduction – asexual by zoospores or aplanospores.
Sexual by zygospores.
- eg. Rhizopus(bread mould) and Albugocandida (causing white rust of crucifers).
Ascomycets (sac fungi)-
- Unicellular (eg. Yeast) or multicellular
- Saprophytic or parasitic.
- Maybe coprophillus (growing on dung) eg. peziza.
- Mycelium septate and branched.
- Reproduction – asexual by exogenously produced conidia.
sexually by Ascospares produced in asci present in fruiting body called Ascocarp.
- egAspergillus, Claviceps, Neurospora, Saccharomyces (yeast) etc.
Basidiomycetes (club fungi) –
- Grow on soil , logs or parasites ( rusts and smuts).
- Mycelium septate and branched and of two types 1) Uninucleate 2) Dikaryophase.
- Reproduction – vegetative by fragmentation sexualby two somatic cells giving rise to Dikaryophase.
- Dikaryophase makes fruiting body Basidiocarp having Basidia.
-Inside basidia (singular basidium) – Karyogamy and meiosis occours.
-Meiosis results in formation of four basidiopores.
Deuteromycetes (Fungi- imperfectil) –
- It is formed class – Group of Fungi whose complete life cycle is not known.-Saprophyte/parasite , mostly decomposers.- eg. Alternaria, colletotrichum, Trichoderma.
Kingdom Plantae –
- Eukaryotic, chlorophyll bearing autotrophic organisms.
- Only few members partialheterotrophs eg. Insectivorus plants (Bladder wort and Venus flytrap).
- Few parasites eg. Cuscuta
- Reproduction – vegetative,asexual and sexual.
- Life cycle shows alternation of generation.
- eg. Algae, Bryophytes,Pteridophyte, Gymnosperms and Angiosperms.
Kingdom Animalia –
- Eukaryotic, Heterotrophic organisms.
- No chloroplast and no cell wall.
-Holozoic mode of nutrition .
- Definite shape and size and capable of locomotion.
- Reproduction – sexual in general
- eg. frog, cockroach, cow, man etc.
Viruses, Viroids and Lichens –
Viruses – Connecting link between living and non living.
- Non cellular structure consisting of protein coat and Nucleic acid
- Can reproduce within a host cell.
- Host cell may be killed.
- Viruses which infect bacteria are called Bacteriophage.
- Tobacco Mosaic Virus (TMV)-
- Protein coat: - capsid consists of capsomers.
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