- Heterotrophic nutrition is of three types : saprotrophic, symbiotic and parasitic.
- Archaebacteria are a group of most primitive prokaryotes characterised by the absence of peptidoglycan in their cell wall.
- Archaebacteria are of three major types: methanogens, halophiles and thermoacidophiles. Methanogens are obligate
anaerobes and produce methane in biogas fermenters, e.g., Methanobacterium, Methanococcus. Halophiles are”salt-loving“
bacteria as they are found in environment with a very high salt concentration. Thermoacidophiles live in extremely acidic
environment that have extremely high temperatures. They are found in hot sulphur springs. - Cyanobacteria (blue-green algae) are photosynthetic prokaryotes that have evolved more than 3 billion years back and paved the
path for evolution of aerobic forms, including aerobic bacteria.
Mycoplasma (PPLO)
Mycoplasmas are the simplest and the smallest of the free living prokaryotes. The organisms are often called PPLOs (Pleuro
pneumonia like organisms). A cell wall is absent and plasma membrane forms the outer boundary of the cell. Due to the absence
of cell wall the organisms can change their shape and are called pleomorphic. Mycoplasmas are heterotrophic in their nutrition.KINGDOM PROTISTA
- Kingdom Protista includes all the unicellular eukaryotic organisms. Phylogenetically, the Kingdom Protista acts as a connecting
link between the prokaryotic Kingdom Monera on one hand and the complex multicellular Kingdoms Fungi, Plantae and Animalia
on the other hand. - These are microscopic unicellular and eukaryotic organisms with cosmopolitan habitat. Many protists are found in water bodies in
the form of plankton. - Many forms have more than one similar or dissimilar nuclei.
- The cell is surrounded by plasma membrane and well developed membrane bound organelles are present inside the cell.
- Five modes of locomotion are recognised in the protista : pseudopodial, flagellar, ciliary, wriggling and mucilage propulsion.
- Mode of nutrition may be photosynthetic, holozoic, saprotrophic, parasitic and symbiotic etc.
- Most of free living protists perform aerobic respiration, however, the parasitic protists respire anaerobically.
- Protists reproduce by both asexual and sexual methods.
- The major groups of protists include chrysophytes, dinoflagellates, euglenoids, slime moulds and protozoans.
- Chrysophytes include diatoms and golden algae. They are found in fresh water as well as in marine environments.
- The cell walls of chrysophytes are embedded with silica and thus are indestructible.
- Chrysophytes produce diatomaceous earth and are the chief ‘producers’ in the oceans.
- Dinoflagellates are mostly marine and photosynthetic. They appear yellow, green, brown and blue or red depending on the
main pigment present in their cells. - Majority of euglenoids are fresh water organisms found in stagnant water. A protein rich layer called pellicle is present instead
of a cell well which makes their body flexible. - Euglenoids are photosynthetic in the presence of sunlight, however, when deprived of sunlight they behave like heterotrophs.
- Slime moulds are saprophytic protists. They form an aggregate called plasmodium which may move and spread over several
feet under favorable conditions. - Protozoans are heterotrophs and live as predators or parasites. They are considered to be primitive relatives of animals.
Major groups of protozoans
Amoeboid protozoans : They live in freshwater, sea water or moist soil. They move and capture their prey with the help of
pseudopodia. 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
such as Trypanosoma cause disease called sleeping sickness.
Ciliated protozoans : These are aquatic and actively moving organisms because of presence of thousands of cilia, e.g., Paramecium.
Sporozoans : These include diverse organisms that have an infectious spore-like stage in their life cycle, e.g., Plasmodium.