IGCSE Biology Paper-2: Specimen Questions with Answers 114 - 115 of 203

Question 114

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Question

MCQ▾

What is the principal source of energy input into a food chain and food web?

Choices

Choice (4)
a.Primary Consume
b.The Sun
c.Secondary Consumer
d.Producer

Answer

b.

Explanation

  • Energy is the ability to do work. The main source of energy for an ecosystem is the radiant energy or light energy derived from the sun. 50 % of the total solar radiation that falls on earth is photo synthetically active radiation (PAR). The amount of solar radiation reaching the surface of the earth is 2 cals/sq. cm/min. It is more or less constant and is called solar constant or solar flux. About 95 to 99 % of the energy is lost by reflection.
  • The light energy is converted into chemical energy in the form of sugar by photosynthesis. Food chain is an order or sequence of different organisms, which are arranged in a way that the food is passed from one type of organism to other organisms such that the organisms of one order or trophic level are the food of the organisms of next order, and here ultimate source of energy is Sun.

Question 115

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Question

MCQ▾

Some yeast, sugar, and water are mixed in a test-tube. The diagrams show the test-tube at the start and after 30 minutes.

Some yeast, sugar and water are mixed in a test-tube

Some Yeast, Sugar and Water Are Mixed in a Test-Tube

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The gas X released in the above reaction is?

Choices

Choice (4)
a.
b. Vapour
c.
d.

Answer

c.

Explanation

Anaerobic respiration

  • It occurs in the absence of molecular oxygen and is called fermentation. In this, the food is only partially oxidized so only a part of energy (5%) is released and of energy remains trapped in the intermediate compounds.
  • It is found in lower organisms like bacteria and yeast. It is also found in certain parasitic worms (Ascaris, Taenia) which live in deficient medium. The organism showing anaerobic respiration, are called anaerobes. These involve one of following reactions.