History of classification
- Aristotle, the Greek philosopher, classified animals based on whether they live on land, in water or in the air.
- Charles Darwin put forward the idea of evolution in 1859, in his book, The Origin of Species.
- Ernst Haeckel, Robert Whittaker and Carl Woese have tried to classify living organisms into broad categories, called kingdoms.
- Carolus Linnaeus classified all the living organisms into two kingdoms namely, Plantae and Animalia.
- Robert Whittaker, in 1969 proposed Five kingdom classification of living organisms.
Moneran characteristics of bacteria
- Habitat - Monerans are found everywhere in hot springs, under ice, in deep ocean floor, in deserts and on or inside the body of plants and animals.
- Nutrition - Autotrophs, heterotrophs, parasitic, symbiotic, commensalism, mutualism.
- Respiration in these organisms vary, they may be obligate aerobes, obligate anaerobes and facultative anaerobes.
- Circulation is through diffusion.
- Movement is with the help of flagella.
- Reproduction is mostly asexual, sexual reproduction is also seen. Asexual reproduction is by binary fission, sexual reproduction is by conjugation, transformation and transduction.
Characteristics of Mycoplasma
- Mycoplasmas or PPLOs are distinct group of prokaryotes.
- Their occurence was demostrated by D. Iwanowsky in 1892.
- They are characterized by the absence of cell wall.
- Mycoplasma cell is delimited by a delicate cell membrane, of successive layers of protein, lipid and proteins, and contains a long double stranded molecule of DNA and RNA granules.
Symptoms and infections caused by Mycoplasma
In humans, Mycoplasma causes pneumonia, joint infection, post patrum fever, chorioamnionitis, urethritis etc. In cattle, it causes pleuropneumonia.
Pneumonia
Pneumonia
- It can be transmitted through airborne droplets from a cough or sneeze.
- When it enters the respiratory tract it multiplies and starts asymptomatic infection.
- On sever condition, it produces symptoms such as fever, headache, sore throat, cough, sputum with blood, chest pain and even death due to cardiac failure.
Properties of Mycoplasma
Nocard and Roux discovered the Mycoplasma. It causes pleuropneumonia in cattle and thus, called as Pleuropneumonia like Organisms (PPLO).
The properties of Mycoplasma are as follows:
The properties of Mycoplasma are as follows:
- They are the smallest cell with 125-250nm in size.
- They lack the cell wall and thus, morphology is not fixed.
- They possess the bacillary and spiral body with filaments and granules.
- They grow in cell-free media that contains lipoprotein and sterol.
Treatment and prevention of disease caused by Mycoplasma
The disease can be diagnosed by the staining method of specimens. Specimens can be isolated from sputum, blood, throat swab and respiratory excretion.
Treatment
Treatment
- Antibiotics are used to treat the disease e.g., tetracycline and erythromycin.
- Medicin: Fluoroquinolone.
- Avoid close contact with infected person.
- The mouth should be covered while coughing or sneezing.
Archaebacteria
- Archaebacteria are ancient group of bacteria living in extreme environments.
- They are characterized by possessing cell walls without peptidoglycan.
- The lipids in their plasma membrane are branched differing from all other organisms.
- They are categorized into methanogens, halophiles and thermoacidophiles.
Types of protists
The kingdom Protista has been broadly divided into three main groups.
- Photosynthetic Protists: They include dinoflagellates, chrysophytes and euglenoids.
- Slime moulds
- Protozoan Protists: They include flagellated protozoans, amoeboid protozoan, sporozoans and ciliated protozoans.
Photosynthetic protists
Dinoflagellates
- Most of them are marine but some occur in fresh water.
- Some show bioluminescence.
- Nutrition is photosynthetic.
- For example, Glenodinium.
- They include diatoms and desmids.
- For example, Spirogyra, Cymbella.
- Occur in fresh water and damp soils.
- Nutrition is holophytic.
- For example, Euglena, Phacus.
Benefits of Protozoa
Protozoa is a unicellular organism found in water. Some have an irregular shape (Amoeba) whereas some have a definite shape (Paramoecium).
Benefits of Protozoa:
a) They are useful for cleaning of dirty water by the process of decomposition.
b) They are useful in scientific research.
c) They are useful in the food chain and especially used as a food for animals.
Benefits of Protozoa:
a) They are useful for cleaning of dirty water by the process of decomposition.
b) They are useful in scientific research.
c) They are useful in the food chain and especially used as a food for animals.
Kingdom Fungi
- Non-green, multicellular, eukaryotic, heterotrophic and saprophytic organisms.
- Made up of tough complex sugar called chitin.
- Most of them are made up of thread like hyphae rather than cells.
- Reproduction in fungi is both by sexual and asexual means.
- For example, yeast, moulds, mushrooms. Most common moulds (fungi) are Aspergillus and Penicillium.
Types of phycomycetes
Phycomycetes is divisible into two groups, oomycetes and zygomycota.
Oomycetes
Oomycetes
- The mycelium is coenocytic.
- Asexual reproduction involves formation of spore containing sacs.
- Gametes are usually nonflagellate.
- Sexual reproduction is by gametangial contact.
- For example, Phytophthora, Albugo.
- The fungal group Zygomycota is most frequently encountered as common bread molds, although both freshwater and marine species exist.
- Most of these live on decaying plant and animal matter found on the substrate.
- They are usually recognized by their profuse, rapidly growing hyphae, but some exhibit a unicellular, yeast-like form of growth.
- Asexual reproduction is by means of spores produced in sporangia borne on the hyphae.
- For example, Mucor, Rhizopus (the bread mould) and Pilobolus.
Structural components of virus
A simple virus particle (virion) consists of a nucleic acid core of genetic material, enclosed within a protein coat (capsid). In general,
- All plant viruses have single-stranded RNA
- Animal viruses have single or rarely double-stranded RNA or double-stranded DNA, and
- Bacterial viruses (bacteriophages) contain mostly double-stranded DNA but can also have single stranded DNA or RNA.
Viruses and bacteria
The difference between viruses and bacteria are as follows:
| Viruses | Bacteria |
| Very small (visible only by electron microscope) | Larger (can be seen by light microscope) |
| Non-cellular. | Single-celled. |
| Have no metabolism. | Have metabolism. |
| Neither grow nor divide. | Grow in size and divide to produce more bacteria. |
| Can be crystallized. | Cannot be crystallized. |
| Command the host cell to produce virus. | Self reproduce. |
| All produce disease in man, animal and plants. | Some harmless, some useful and some disease producing. |
Viroids
- Viriods are small single-stranded circular RNA agents which infect plants.
- They differ from RNA viruses in three major aspects: their minute size (they are non-quarter of the size of the smallest RNA virus, i.e., 250-400 bases); the genome does not encode any proteins and they are not encapsidated.
- Viroid infections is mediated mechanically.
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