Lakshya Education MCQs

Question: Rhizobium fixes nitrogen by
A.Converting gaseous nitrogen to ammonia
B.Converting gaseous nitrogen to nitrite
C.Converting gaseous nitrogen to nitrate
D.None of the above
Answer: Option A
: A

Rhizobium converts nitrogen to ammonia, Nitrosomonas converts the ammonia to nitrite, whereas Nitrobacter converts the same ammonia to nitrate. It is easiest for plants to take up nitrogen in the form of​ nitrates as apposed to gaseous nitrogen.

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Question 1. Aeration of water during wastewater treatment removes which of these?
  1.    Human waste
  2.    Bacteria
  3.    Germs
  4.    Insoluble items
Answer: Option A
: A

In biological treatment of sewage water, microbial flocs (group of aerobic bacteria associated with fungi forming a mesh like network) are used in treatment of partially treated effluent in aeration tanks. Aeration of wastewater facilitates the growth of aerobic bacteria which can degrade the solubilised and suspended organic matter in sewage water. Hence they specifically act on organic wastes like human wastes, animal wastes, kitchen wastes etc,
Question 2. Secondary sewage treatement is a ___.
  1.    Physical process that is used to remove small and large particles 
  2.    Biological process that is used to remove dissolved and suspended organic compounds
  3.    Chemical process that is used to remove radioactive compounds
  4.    All of the above
Answer: Option B
: B

Secondary sewage treatment is a biological process that is used in theremoval of suspended and dissolved organic compounds from the sewage water by using microbial flocs (Group of anaerobic bacteria that are associated with fungal filaments to form mesh-like structures). It aims toachieve a certain degree ofeffluentquality by using asewage treatmentplant with primary treatment for separation of removable (large) and settleable (small) solids followed by biological process to remove dissolved and suspended organic compounds. These flocs greatly aid in the reduction of BOD of water so that it can be disposed safely without polluting water bodies.
Question 3.  Fungal partners in mycorrhiza are ______ in nature.
  1.    parasitic
  2.    symbiotic
  3.    saprophytic
  4.    None of these
Answer: Option B
: B

Mycorrhiza is an association of a fungus which grows in the roots of a plant in a symbiotic relationship with the plant. The relationship between the fungus and root exists because the fungi absorb phosphorus from the soil and pass it to the plant and inturn, the fungi get a safe environment for their survival. In most cases, fungi can be both saprophytic and parasitic in nature where they only work for self benefit. But in mutualistic and symbiotic associations the fungal partner and the other partner, in this case the plant, gain equal benefits from their interactions with each other.
Question 4. An apprentice of a baker fails to get the soft and fluffy texture of bread as his master does in his first attempt at making bread. What could be the likely reason, considering that he baked the bread for as long as his master did?
  1.    The apprentice did not bake the bread at the right temperature
  2.    The bread dough was not made from good quality wheat
  3.    The bread dough did not have enough water, making it hard
  4.    The bread dough did not ferment properly before baking
Answer: Option D
: D

For bread to become soft and fluffy, the dough must undergo fermentation. When the bread dough ferments, some amount of carbon dioxide is released by the action of yeast on the sugars which creates a lot of gas bubbles in the dough. When baked, these gas bubbles appear as holes in the bread and make the bread fluffy and light.
Question 5. Which one of the following is not a bio fertilizer?
  1.    Rhizobium
  2.    Nostoc
  3.    Mycorrhiza
  4.    Agrobacterium
Answer: Option D
: D

Biofertilizersare defined as preparations containing living cells or latent cells of efficient strains of microorganisms that help crop plants uptake nutrientsdue to their interactions in the rhizosphere (narrow region of soil that is directly influenced by root secretions and associated soil microorganisms)when applied through seed or soil. Examples includeRhizobium, Nostoc etc.Mycorrhizais a fungi that is in a symbiotic association with roots of plants and it helps in absorption of phosphate from the soil. Agrobacterium is a gram negative bacterium that causes tumors in plants. It is well known for its ability to transfer DNA intoplantsand for this reason it has become an important tool for genetic engineering. A. tumefaciens causes crown-gall disease in plants. A. tumefaciens is therefore not a biofertilizer.
Question 6. Microbes are those organisms that can be viewed only under a ___ 

: Microbes are organisms that are so small that they cannot be viewed by our naked eye. These organisms are usually unicellular although some may be multicellular. However, they can all be viewed and studied only under a microscope. Hence their name - microbes.

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