This set of Class 12 Biology Chapter 14 Multiple Choice Questions & Answers (MCQs) focuses on “Ecosystem – Phosphorus Cycle”.
1. Which one of the following is a major constituent of biological membranes, nucleic acids, and cellular energy transfer systems?
a) Potassium
b) Phosphorous
c) Selenium
d) Cobalt
View Answer
Explanation: The phosphorous is the second most abundant mineral of the human body and constitutes 1 % of the total body weight. It is one of the following is a major constituent of nucleic acids, biological membranes, and cellular energy transfer systems.
2. Which of the following component is used to make shells, bones, and teeth by animals?
a) Phosphorous
b) Sodium
c) Gallium
d) Argon
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Explanation: The phosphorous is one of the following is a major constituent of nucleic acids, biological membranes, and cellular energy transfer systems. It is also used to make shells, bones, and teeth by animals.
3. Who is the natural reservoir of phosphorous?
a) Atmospheric gases
b) Rocks
c) Water
d) Dead organisms
View Answer
Explanation: The sedimentary rocks are known as the natural reservoir of phosphorous. They contain phosphorous in the form of phosphates known as phosphorite. It contains almost 4% to 20% of phosphate.
4. Which element is not released during respiration in the atmosphere?
a) Nitrogen
b) Cobalt
c) Carbon
d) Phosphorous
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Explanation: The respiration is the process in which the organisms exchange gases with the environment. In this, the organisms take in the atmospheric oxygen for various cellular activities and release carbon dioxide. Phosphorous is not released during respiration in the atmosphere.
5. How is the gaseous exchange of phosphorus between organisms and the environment?
a) Maximum
b) Moderate
c) Negligible
d) No exchange
View Answer
Explanation: The phosphorous is one of the following is a major constituent of nucleic acids, biological membranes, and cellular energy transfer systems. Unlike carbon, there is a negligible exchange of gaseous phosphorus between organisms and the environment.
6. Which one of the following is the simplified sequence of phosphorus cycling in a terrestrial ecosystem?
a) Soil → Producers → Rock minerals → Consumers → Decomposers
b) Rock minerals → Soil → Producers → Consumers → Decomposers
c) Rock minerals → Decomposers → Producers → Consumers
d) Decomposers → Rock minerals → Consumers → Producers
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Explanation: The phosphorous cycle starts with rock materials and ends with the decomposers. The phosphorous enters the ecosystem through rock minerals and, there is a negligible exchange of gaseous phosphorus between organism and environment.
7. How do herbivores and other animals obtain phosphorous?
a) Soil
b) Rocks
c) Water
d) Plants
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Explanation: The phosphorous is one of the following is a major constituent of nucleic acids, biological membranes, and cellular energy transfer systems. The plants are the source of phosphorous for herbivores and other animals.
8. Which of the biochemical cycle is without an atmospheric component?
a) Nitrogen cycle
b) Oxygen cycle
c) Phosphorous cycle
d) Carbon cycle
View Answer
Explanation: The sedimentary rocks are known as the natural reservoir of phosphorous. It enters in the ecosystem through rock minerals. The biochemical cycle is without an atmospheric component is the phosphorous cycle.
9. Which of the following is a major constituent of DNA and RNA?
a) Calcium
b) Cobalt
c) Selenium
d) Phosphorous
View Answer
Explanation: The phosphorous is one of the following is a major constituent of nucleic acids, biological membranes, and cellular energy transfer systems. It is the second most abundant mineral of the human body and constitutes 1 % of the total body weight.
10. Which biogenetic element is obtained from crystalline rocks?
a) Argon
b) Helium
c) Phosphorous
d) Magnesium
View Answer
Explanation: The crystalline, sedimentary rocks are known as the natural reservoir of phosphorous. They contain phosphorous in the form of phosphates known as phosphorite. It contains almost 4% to 20% of phosphate.
11. Which of the following is known as the natural reservoir of phosphorous?
a) Fossils
b) Rocks
c) Animals
d) Water
View Answer
Explanation: The crystalline, sedimentary rocks are known as the natural reservoir of phosphorous. They contain phosphorous in the form of phosphates known as phosphorite. It contains almost 4% to 20% of phosphate.
12. The phosphate by weathering of rocks firstly becomes available to which organisms?
a) Decomposers
b) Consumers
c) Producers
d) Detritivores
View Answer
Explanation: The phosphorous enters in the ecosystem through the weathering of rock minerals. This phosphorous then enters soil that is taken up by the producers. Then it is passed on to consumers and then to decomposers.
13. In which form do the producers directly provide phosphorous to detritus?
a) Weathering
b) Litterfall
c) Fecal matter
d) Salts
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Explanation: The dead plant materials that falls on the ground in the form of litter are known as litterfall. This litter includes leaves, bark, needles, twigs, cladodes, etc. It also consists of some amount of soil.
14. What is the killing of aquatic life due to the depletion of oxygen because of the excessive growth of algae due to the over-abundance of phosphorous in the coastal areas called?
a) Leaching
b) Respiration
c) Photosynthesis
d) Eutrophication
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Explanation: Eutrophication is the process that leads to the killing of aquatic life due to the depletion of oxygen because of the excessive growth of algae due to the over-abundance of phosphorous in the coastal areas. Eutrophication is also known as hypertrophication and is the result of an increase in minerals in a water body.
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