Biological Classification Test - 6

Plant decomposers are saprophytic fungi and bacteria that absorb nutrients from non-living organic material such as fallen plants material and the wastes of living organisms and convert them into organic forms. The bacteria belong to kingdom-Monera while fungi belong to Fungi.

The archaebacteria are the primitive, single-celled, prokaryotic organisms. These are the ancient and oldest living organisms. These were the first organism which evolved on the Earth. These organisms have evolved to survive in the extreme conditions like the halophiles, thermophiles, acidophiles, methanogens, etc. 

• Decomposers are organisms that are involved in the degradation of dead and decaying organisms. 

• They are heterotrophs because they are dependent on others organisms to get their food such as bacteria and fungi.

• The decomposition is a step by step process in simplifying the constituents of the dead body.

• The steps include fragmentation, leaching, catabolism, humification and mineralization. These steps follow one another to finally degrade the body properly.

Mycorrhiza is the symbiotic relationship between fungi and roots of the higher plants where fungi help in increasing the surface area of absorption. They also help in the mineral uptake by the plant in return plant provides protection and shelter and food to the fungi.

Photosynthetic bacteria have chromatophores which are membrane bound vesicular structures which are extensions of cytoplasmic membrane. They contain photosynthetic pigments along with enzymes and electron carriers for photosynthetic phosphorylation. These pigment are bacteriochlorophyll and bacteriop- haeophytin. Leucoplasts, chloroplasts and chromoplasts are different types of plasids which occur in plastids and some protistans.

Monera kingdom consists of unicellular prokaryotic organisms. It includes bacteria like Escherichia, Cyanobacteria (Blue green algae). They lack membrane-bound organelles. They also have genetic material without nuclear envelope. Hence, they do not contain true nucleus.

Escherichia coli is used extensively in biological research like protein engineering and genetic research due to several reasons. It has relatively small genome size. It is easily cultured. It has a high growth rate compared to complex organisms. It is a well-studied model organism.

Cell of diatoms are surrounded by a silica-based shell/cell wall called as frustules which is composed of two overlapping halves (the epitheca and the hypotheca). Presence of numerous tiny pores in frustules connects the protoplast of the cell with the outside environment. Calcium carbonate is present in cell wall of red algae and pellicle of protozoans; it makes the cell permeable to small molecules but impermeable to macromolecules. Red algae secrete calcium carbonate shells which are accumulated in sea bottom and forms red corals. Keratin is an α-helix protein and is present in skin, hair or nails of animals where it is acted upon by keratinase enzyme of dermatophytes, the fungi that cause cutaneous mycoses. Calcium oxalate is poisonous, even fatal substance which is the main constituent of human kidney stone; it is not present in cell wall.

Virus is without necessary metabolic enzymes, hence, free virus are inert particles incapable of any vital activities and uses host machinery. Virus is regarded as obligate parasite and have characteristic of both living and non-livings.

The structure of a virus consists of a core of nucleic acid surrounded by a protein envelope which is called a capsid. In its infective form, the virus particle is called a virion.