MCQs Based On Environment – (5)

Correct Option: 1. Parasitism.
Explanation : Biotic Interaction is the interaction between the organisms living on the earth. This interlinking with each other is necessary for the survival of ecosystem. Parasitism is one such interaction where one organism is benefitted and other is harmed. For Ex. A blood sucking tick sucks blood from the body of cattle and the cattle looses blood. So the tick is benefitted and the cattle is harmed. Following are the types of Biotic interaction and there outcome for the species involved.
• Mutualism : – Species (1): Benefitted. Species (2): Benefitted.
• Commensalism : – Species (1): Benefitted. Species (2): Neither Benefitted nor harmed.
• Competition : – Species (1): Harmed. Species (2): Harmed.
• Predation : – Species (1): Benefitted. Species (2): Harmed.
• Parasitism : – Species (1): Benefitted. Species (2): Harmed.
• Amensalism : – Species (1): Harmed. Species (2): Neither benefitted nor harmed.
• Neutralism : – Species (1): Neither benefitted nor harmed. Species (2): Neither benefitted nor harmed.

Correct Option: 3. Amensalism.
Explanation : Biotic Interaction is the interaction between the organisms living on the earth. This interlinking with each other is necessary for the survival of ecosystem. Amensalism is one such interaction where one organism is harmed and other is unaffected. For Ex. A small tree will have retarded growth due to lack of sunlight if it is present under the shades of large tree. In this case small tree is harmed and the large tree is unaffected.

Correct Option: 2. Nitrogen is absorbed by plants in its original form.
Explanation : Plants cannot absorb nitrogen in its original form. Nitrogen needs to be fixed before it can be taken up by the plants. Nitrogen “Fixation” means converting it into ammonia, nitrites or nitrates. Nitrogen is an essential constituent of protein which is the basic building block of all living tissue. Nitrogen is fixed by microorganism such as bacteria (Rhizobium) and blue green algae. Release of nitrogen oxides (NOx) in the atmosphere cause acid rain.

Correct Option: 1. Pseudomonas bacteria.
Explanation : Pseudomonas bacteria cannot fix nitrogen into ammonia or nitrites. They are denitrifying bacteria. They convert nitrites/nitrates into free nitrogen. Whereas free living aerobic Azotobacter and anaerobic Clostridium are nitrogen fixing bacteria. And hence convert nitrogen into ammonia and then to nitrites/nitrates. Symbiotic bacteria like Rhizobium and blue green algae (Anabaena, Spirulina) also fixes the nitrogen. Some atmospheric phenomenon such as Thunder and lightning also fixes nitrogen to some extent.

Correct Option: 4. Nitrogen.
Explanation : Nitrogen enters into the environment mainly through gaseous cycle of Biogiochemical cycle. Whereas Magnesium, calcium & phosphorous enter into the environment through sedimentary cycle of Biogiochemical cycle. The elements involve in sedimentary cycle flows through erosion, volcanic eruption, sedimentation, mountain building and biological transport through the excreta of marine birds.