Which one of the following is a saprophyte ?
- A.Cuscuta
- B.Rhizopus
- C.Spirogyra
- D.Grass
Correct answer
Explanation
The correct answer is B, Rhizopus. Rhizopus, the bread mould, feeds on dead and decaying organic matter, which is exactly what a saprophyte does.
A saprophyte gets its food by releasing digestive enzymes onto dead matter such as stale bread, fruit or leaf litter and then absorbing the simple nutrients that result. Many fungi, including Rhizopus, Mucor and mushrooms, and many bacteria live this way. By breaking down dead remains they act as decomposers and return nutrients to the soil. Rhizopus is easily seen as the black, cottony growth on moist bread kept for a few days.
A is wrong because Cuscuta, the dodder, is a parasite that draws food from a living host plant through its haustoria. C is wrong because Spirogyra is a green alga that makes its own food by photosynthesis. D is wrong because grass is a green plant and is therefore autotrophic.
Exam tip: Rhizopus and mushrooms are saprophytes, Cuscuta is a parasite, and green plants and algae are autotrophs.
Practice Questions
View allWhich one of the following is the purest form of Carbon ?
- A.Charcoal
- B.Coke
- C.Fullerene
- D.Carbon black
Show answer
Fullerenes are made of carbon atoms alone, with no surface to trap other substances, so they are counted as the purest form of carbon.
Read the full explanation →A planet has a mass M₁ and radius R₁. The value of acceleration due to gravity on its surface is g₁. There is another planet 2, whose mass and radius both are two times that of the first planet. Which one of the following is the acceleration due to gravity on the surface of planet 2?
- A.g₁
- B.2g₁
- C.g₁/2
- D.g₁/4
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Surface gravity is g = GM/R², so doubling the mass doubles g while doubling the radius divides it by four, leaving g₁ × 2/4 = g₁/2.
Read the full explanation →Which one of the following is the major constituent of biogas ?
- A.Carbon dioxide
- B.Nitrous oxide
- C.Methane
- D.Oxygen
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Methane makes up the largest share of biogas, usually about 55 to 75 per cent, and it is the gas that burns.
Read the full explanation →A lemon kept in water in a glass tumbler appears to be larger than its actual size. It is because of
- A.reflection of light
- B.scattering of light
- C.refraction of light
- D.polarization of light
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The lemon looks bigger because light from it bends as it passes from water through the curved glass into air.
Read the full explanation →Which one of the following conclusions could not be derived from Rutherford's α-particle scattering experiment?
- A.Most of the space in the atom is empty.
- B.The radius of the atom is about 10⁵ times the radius of the nucleus.
- C.Electrons move in a circular path of fixed energy called orbits.
- D.Nearly all the mass of the atom resides in the nucleus.
Show answer
. Orbits of fixed energy were proposed by Niels Bohr in 1913; Rutherford's experiment said nothing about the energy of electrons.
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