.jpg)
DOWNLOAD NOTES PDF - DOWNLOAD QUESTIONS
Aristotle’s classification
- Aristotle was the earliest to attempt a more scientific basis for classification of organisms.
- He classified plants to trees, shrubs & herbs and animals into 2 groups- those with red blood & without red blood.
Linnaeus’s Two-kingdom classification
- Linnaeus (1758) classified organisms into Two Kingdoms- Kingdom Plantae & Kingdom Animalia.
Drawbacks of 2-kingdom classification:
- Prokaryotes (Bacteria, cyanobacteria) and eukaryotes (fungi, mosses, ferns, gymnosperms & angiosperms) were included under ‘Plants’ based on the presence of cell wall. But they are widely differed in other characteristics.
- It included the unicellular and the multicellular organismsin same group. E.g. Chlamydomonas and Spirogyra wereplaced under algae.
- It did not differentiate between the heterotrophic fungi and the autotrophic green plants. Fungi have chitinous cell wall while the green plants have cellulosic cell wall.
Five Kingdom Classification
- RH. Whittaker proposed the five-kingdom classification in 1969.
- This classification was based upon certain characters like mode of nutrition, thallus organization, cell structure, phylogenetic relationships (evolutionary relationship) and reproduction
- This five kingdoms include Monera, Protista, Fungi, Plantae and Animalia
KINGDOM MONERA
- Bacteria are the sole members of this kingdom Bacteria occur almost every where including extreme habitats such as hot springs, deserts, so deep oceans
- Bacteria are grouped under four categories based on their shape 1. Coccus (Spherical) 2. Bacillus (Rod-shaped) 3. Vibrium (Comma-shaped 4Spirillum (Spiral)
- Bacterial structure is very simple but they are very comples in behaviour and shows extensive metabolic diversity.
- Some bacteria are autotrophic ie they synthesize food from inorganic substrates.
- Majority are heterotrophs ie, they depend on other organisms or on dead organic matter for food).
a)ARCHAEBACTERIA
- 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 cell wall structure (absence of peptidoglycan)
- This nature of cell wall is responsible for their survival in the extreme conditions.
- Methanogens are present in the guts of several ruminant animals like coups and buffalo, which is responsible for production of biogas (methane) from dung of these animals
b).EUBACTERIA
- They are called as true bacteria.
- They have rigid cell wall, if motile they have 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 cells called heterocyst to perform nitrogen fixation (Nostoc and aneabana)
- Chemosynthetic bacteria oxidize inorganic substances like nitrate, nitrite, ammonia etc, to produce ener and help in recycling of nitrogen, phosphorous, sulphur etc.
- Heterotrophic bacteria are most abundant and act as decomposer They are helpful in the production of curd, antibiotic and faxing nitrogen in leguminous plants.
- Some of them are pathogenic and cause disease like cholera, typhoid, tetanus and citrus canker.
- Bacteria reproduce mainly by fission, also produce sporelendospore) in unfavorable condition. Reproduce sexually by transfer of DNA form one bacteria to other, the process called conjugation.
Mycoplasma
- They are the smallest living cells.
- They were formerly known as PPLO (Pleuropneumonia like organism).
- They lack cell wall and can survive without oxygen. They cause disease in plants and animals.
KINGDOM PROTISTA
- All are unicellular and eukaryotic
- Mostly aquatic, can live in moist places.
- Forms a connecting link between plants, animals and fungi.
- Kingdom Protista includes Chrysophytes, Dinoflagellates, Eugleoids, slime mould and Protozoans.
1 CHRYSOPHYTES
- They includes diatoms and golden algae (desmaids), found in fresh water as well as marine water.
- In diatoms cell wall forms two thin overlapping plates which fit together as in soap box
- The deposition of silica embedded cell walls of diatoms in ocean bottom is known as diatomaceous earth
- The soil of diatomaceous earth is gritty and it is used in polishing, filtrations of oils and syrups,
- They are chief producer in oceans.
2 DINOFLAGELLATES
- They are basically unicellular, mobile, biflagellate and photosynthetic protists.
- Predominant colour is golden brown but yellow, green, red and even bloe also exists.
- Some Dinoflagellates like Gymnodinium and Gonyaulax grow in large number in the sea and make the w look red and cause the so called "Red tide".
3. EUGLENOIDES
- 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
4.SLIME MOULDS
- They are saprophytic protists and feeds on decaying twigs and leaves.
- Under favorable condition, they form an aggregation called plasmodium which produce fruiting bodies bearing spores.
- The spores are extremely resistant and survive for many years.
- Example-Physarum, Fuligo
5.PROTOZOANS
- All protozoans are heterotrophs and live as predators or parasites. They are considered as primitive relatives of animals
- There are four major groups of Protozoans
a) AMOEBOID PROTOZOANS
- Move and Catch prey using pseudopodio, e.g, Amoeba
- Many forms have silica shells on their surface.
- Some of them are parasitic eg. Entamoeba
b) FLAGELLATED PROTOZOANS
- Either free living or parasitic
- They have flagella.
- Couse disease like sleeping sickness eg, Trypanosoma
c).CILIATED PROTOZOANS
- These are aquatic, actively moving organisms due to presence of thousands of cilia, eg, Paramecium
- They have a cavity called gullet that opens to outside the cell. Eg. Paramecium, Vorticella
d).SPOROZOANS
- Lack any locomotory organelle.
- All members are parasitic
- Have infective spore like stage in life cycle, eg, Plasmodium which causes Malaria
IIl KINGDOM FUNGI
- Fungi are eukaryotic heterotrophic organisms.
- They show a great diversity in morphology and habitat.
- Common types include.
- Yeast (used to make bread and beer.
- Puccinia (causative organism of wheat-rust disease)
- Penicillium (Source of antibiotic called penicillin) They are filomentous, with the exception of unicellular Yeasts.
- The body of fungi consists of long, slender thread-like structures called hyphae. The network of hyphae is known as mycelium.
- Some hyphae are continuous tubes filled with multinucleated cytoplasm. These are called coenocytic/aseptate hyphae.
- Others have septae or cross walls in their hyphae they are called septate hyphae.
- Fungal cell wall is made up of chitin & polysaccharides.
- Mest fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes
- The fungi that depend on living plants and animals for their food are called parasites. Fungi can also live as symbionts in association with algae as lichens and with roots of higher plants as mycorrhiza.
Reproduction in Fungi
- Fungi reproduce vegetatively by fragmentation, budding or fission.
- Asexual reproduction takes place through spores called conidia, sporangiospores, aplanospores or zoospor Fungi reproduce sexually through oospores, ascospores, zoospore or basidiospores.
- Sexual cycles involves the following steps
- Plasmogamy: fusion of protoplasms between two motile or non-mobile gametes
- Karyogamy fusion of two nucle Meiosis: zygote undergoes meiosis resulting in haploid spores.
- In higher fungi, karyogamy is delayed and occors just before meiosis. In such cases opposite nuclei remain paired (non,Dikaryon) before fusion. Sock cells are called dikaryotic cell
- Based on the morphology of the mycelium, mode of spore formation and fruiting bodies,
- Kigdom fungi are classified into 4 classes on the basis of morphology of the myceliom
- mode of spore formation and fruiting bodies.
1.PHYCOMYCETES
- They are found in aquatic habitat and on decaying wood in moist and damp places.
- Some are obligate parasites on plants.
- The mycelium is made up of aseptate and coenocytic hyphae.
- Asexual reproduction by zoospores( motile) or aplanospores (non-motile).
- Spores are produced endogenously in sporangium.
- Reproduce sexually by means of zygospores formed by the fusion of morphologically similar(isogamous) or morphologically dissimilar (anisogamous) gametes
- Example-Mucor, Rhizopus, Albogo etc.
2.ASCOMYCETES (THE SAC FUNGI)
- They are saprophytic, decomposers, parasitic or coprophilous (growing on dung).
- Mycelium is composed of branched and septate hyphae.
- Asexual spores are called conidia produced exogenously on the conidiophores. Sexual spores are called ascospores produced endogenously in sac like ascos.
- These are arranged in different types of fruiting bodies called Ascocarp.
- Example-Yeast (Unicellular), Neurospora, Asperigillus, Claviceps etc.
3.BASIDIOMYCETES (THE CLUB FUNGI)
- Common known forms called mushrooms, bracket fungi or puffballs.
- Mycelium is septate and branched.
- Asexual spores generally are not found Conchas
- Vegetative reproduction by fragmentation.
- During sexual reproduction plasmogamy of vegetative or somatic cells of different strains rest dikaryotic hyphae.
- Basidiom is formed from this dikaryotic hyphae.
- Karyogamy and meiosis takes place in the basidiom .
- Four basidiospores are developed exogeneously on the basidium.
- Basidia are arranged in fruiting body called basidiocarp.
- Example- Agaricus (Mushroom), Ustilago (smut), Puccinia (rust).
DEUTEROMYCETES (THE FUNGI IMPERFECTI)
- Commonly known as imperfect fungi because only the asexual or vegetative phases of these
- fungi are known 。
- Sexual reproductive phase (perfect stage) is not known for them.
- Once sexual form is discovered the member is moved to Ascomycetes or Basidiomycetes
- Mycelium is septate and branched.
- Are saprophytic, parasitic or decomposers.
- Example- Alternario, Trichoderma, Colletotrichum.
VIRUS
- Viruses are non-cellular organisms having inert crystalline structure outside the living cell.
- Once they enter the living cell, they take over the machinery of living cell to replicate themselves. The name virus (means venom or poisonous fluid) was given by Pasteur.
- D.J. Ivanowsky (1892) recognized certain microbes that cause mosaic disease of tobacco.
- They were smaller than bacteria because they passed through bacteria-proof filters. M.W. Beijerinek (1898) demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants and called the fluid as Contagium vivum fluidum (infectious living fluid).
- W.M. Stanley (1935) showed that viruses could be crystallized and crystals consist largely of proteins.
- In addition to proteins, viruses also contain genetic material (RNA or DNA). No virus contains both RNA DNA.
- A virus is a nucleoprotein and the genetic material is infectious.
- Usually plant viruses have single stranded RNA; bacteriophages have double stranded DNA and animal viruses have single or double stranded RNA or double stranded DNA
VIROIDS
- The protein coat called capsid is made of small subunits called capsomeres, protects the nucleic acid.
- These capsomeres are arranged in helical or polyhedral geometric forms.
- Viroids are discovered by T.O.Diener as neu infectious agent smaller than virus causing potato spindle tuber disease.
- They are free RNA without protein coat
PRIONS
- These are abnormally folded protein particles responsible for several neurodegenerative diseases. It's a protein particle without genetic material.
- Most notable disease caused by prions are bovine spongiform encephalopathy (BSE)/mad cow diseas in cattle and Cr-Jacob disease (CJD) in humans.
LICHENS
- Lichens are symbiotic associations between algae and fungi.
- The algal component is known as phycobiont and fungal component as mycobiont.
- Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner,
- They are good pollution indicators as they do not grow in polluted area.