Q10. Which of the following needs can photosynthesis meet for autotrophic organisms: I carbon, II water, III energy?
[SSC CHSL — 6 March 2018, Shift 2]
(A) I only
(B) III only
(C) I and III
(D) I, II and III
Answer: (C) I and III
Explanation: Photosynthesis incorporates carbon from carbon dioxide into organic compounds and captures light as usable chemical energy. Water is an input consumed in the overall process, not a requirement manufactured by it. Hence carbon acquisition and energy capture are the relevant outcomes.
Q9. Which energy conversion correctly describes photosynthesis?
[CGPSC State Service Preliminary Examination — 2017]
(A) Solar energy to heat energy
(B) Solar energy to kinetic energy
(C) Solar energy to potential energy in a mechanical sense
(D) Light energy to mechanical energy
(E) None of these
Answer: (E) None of these
Explanation: Photosynthesis converts radiant energy into chemical energy stored in sugars. None of the listed mechanical or thermal conversions accurately identifies this principal transformation. The question therefore requires the final choice. Chemical energy later supports life processes and ecosystem food chains.
Q8. Photosynthesis proceeds in the presence of chlorophyll and which essential environmental factor?
[SSC CGL Tier-I — 10 August 2017, Shift 2]
(A) Water alone
(B) Mineral nutrients alone
(C) Carbon dioxide alone
(D) Sunlight
Answer: (D) Sunlight
Explanation: Chlorophyll is the pigment that absorbs light and enables photosynthesis to proceed. Green plants also require carbon dioxide and water as raw materials, but the missing condition in this question is sunlight. Captured radiant energy supports formation of carbohydrates.
Q7. Cuscuta growing over trees and shrubs is an example of which nutritional association?
[MP Police Constable — 23 July 2016, Shift 2]
(A) Autotrophic nutrition
(B) Parasitic nutrition
(C) Saprotrophic nutrition
(D) Insectivorous nutrition
Answer: (B) Parasitic nutrition
Explanation: Cuscuta, commonly called amarbel, is a stem parasite that obtains water and nutrients from a host plant through specialised absorbing structures. Since it depends on living host tissues, its mode is parasitic rather than saprotrophic or insectivorous.
Q6. Which event does NOT occur in the light-dependent stage of photosynthesis?
[RPSC Second Grade Science Teacher — 2015]
(A) Photolysis of water
(B) Reduction of carbon dioxide
(C) Photophosphorylation
(D) Reduction of NADP+
Answer: (B) Reduction of carbon dioxide
Explanation: Water splitting, ATP production and formation of NADPH are associated with the light reactions in chloroplast thylakoid membranes. Carbon dioxide reduction belongs to the Calvin cycle, which uses ATP and NADPH produced by the light-dependent reactions.
Q5. The lichen community that can begin succession on bare rock is a symbiotic association between which organisms?
[UPSC CSE Preliminary Examination — 24 August 2014]
(A) Algae and bacteria
(B) Algae and fungi
(C) Bacteria and fungi
(D) Fungi and mosses
Answer: (B) Algae and fungi
Explanation: A lichen generally consists of a photosynthetic alga associated with a fungus. The alga provides carbohydrates; the fungus helps secure water, minerals and protection. Their ability to grow on exposed rock makes many lichens important pioneer organisms in ecological succession.
Q4. Some organisms can photosynthesise using parts of solar radiation invisible to humans. Which group includes such organisms?
[UPPSC Civil Services Preliminary Examination — 2013]
(A) Trees
(B) Ordinary green algae only
(C) Certain bacteria
(D) Fungi
Answer: (C) Certain bacteria
Explanation: Certain photosynthetic bacteria possess pigments that can capture wavelengths beyond the visible range, including near-infrared radiation. Most green plants primarily use visible light through chlorophyll. Fungi lack chlorophyll and obtain organic food heterotrophically rather than performing photosynthesis.
Q3. What is the principal function of xylem tissue in plants?
[WBCS Preliminary Examination — 2012]
(A) Carrying out photosynthesis
(B) Transporting water and mineral nutrients
(C) Storing every food reserve
(D) Carrying only enzymes
Answer: (B) Transporting water and mineral nutrients
Explanation: Xylem moves water and dissolved mineral ions through the root, stem and leaf system. These substances are essential for photosynthesis and growth. The prepared food is predominantly transported by phloem, not by xylem, making transport of water and minerals correct.
Q2. Which plant commonly opens its stomata during the night and closes them during the day?
[WBCS Preliminary Examination — 2005]
(A) Water lily
(B) Cactus
(C) Sunflower
(D) Fern
Answer: (B) Cactus
Explanation: Many cacti use crassulacean acid metabolism, opening stomata at night to acquire carbon dioxide while limiting daytime water loss. The carbon dioxide can then be used in daytime photosynthesis. This adaptation supports survival in hot, dry environments.
Q1. What happens to energy during photosynthesis?
[WBCS Preliminary Examination — 2002]
(A) Oxygen must be supplied as an essential input
(B) A catabolic breakdown reaction predominates
(C) Light energy is stored as chemical potential energy in food
(D) Stored food energy is released as heat
Answer: (C) Light energy is stored as chemical potential energy in food
Explanation: Photosynthesis is an anabolic food-making process. Sunlight captured by chlorophyll is ultimately stored as chemical potential energy in carbohydrates such as glucose. Releasing this stored energy through breakdown of food is characteristic of respiration, not photosynthesis.
