76: Which one of the following organisms can serve as a bio-fertilizer for rice crop?
(a) Blue green algae
(b) Rhizobium sp
(c) Mycorrhizal fungi
(d) Azotobacter sp
Explanation:
Blue green algae (Cyano bacteria) and Azolla are used for the low land rice cultivation as algal bio-fertilizers. Fixes 20-30 kg N/ha per year in rice field. Ex. : Anabaena, Nostoc etc.
77: Biofilms are
(a) colour films used by biologists to photograph living organisms
(b) photomicrographs of microorganisms from various habitats
(c) accumulations of microorganisms at surfaces such as those of a rock, a tooth or an oil droplet
(d) photographic films made through fermentation processes of certain industrial microorganisms
78: Which of the following statements is / are correct regarding vegetative propagation of plants ?
1. Vegetative propagation products clonal population.
2. Vegetative propagation helps in eliminating the virus.
3. Vegetative propagation can be practiced most of the year.
Select the correct answer using the code given below:
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
79: Which bacterial strain, developed from natural isolates by genetic manipulations, can be used for treating oil spills ?
(a) Agrobacterium
(b) Pseudomonas
(c) Nitrosomonas
(d) Clostridium
Explanation:
Pseudomonas aeruginosa is a common bacterium which can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has thus coloized many natural and artificial environments. It uses a wide range of organic material for food; in animals, the versstility enables the organism to infect damaged tissues or people with reduced immunity. The symptoms of such infections are generalized inflammation and sepsis. If such colonizations occur in critical body organs, such as the lungs, the urinary tract, and kidneys, the results can be fatal. Because it thrives on most surfaces, this bacterium is also found on and in medical equipment, including catheters, causing cross-infections in hospitals and clinics. It is implicated in hot-tub rash. It is also able to decompose hydrocarbons and has been used to break down tarballs and oil spills.
80: At which stage in its life-cycle does the silkworm yield the fibre of commerce?
(a) Egg
(b) Larva
(c) Pupa
(d) Imago
Explanation:
Pupa stage of Silkworm yield fibre of commerce. The larve while entering the pupal stage makes a pupal case around it by secreting a protein fibre (Fibroin).