IGCSE Biology Paper-2: Specimen Questions with Answers 168 - 169 of 203

Question 168

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Question

MCQ▾

Which process produces heat to maintain a person’s body temperature?

Choices

Choice (4)
a.Nutrition
b.Respiration
c.Excretion
d.Reproduction

Answer

b.

Explanation

The respiratory system has many functions. Besides inhale (breathe in) and exhale (breathe out), it also:

  • Allows you to talk and to smell.
  • Brings air to body temperature and moisturizes it to the humidity level your body needs.
  • Delivers oxygen to the cells in your body.
  • Removes waste gases, including carbon dioxide, from the body when you exhale.
  • Protects your airways from harmful substances and irritants.
  • Maintain body temperature by generating heat.

Question 169

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Question

MCQ▾

Which process is used to transport sucrose from the leaves of a plant to its flowers?

Choices

Choice (4)
a.Translocation
b.Diffusion
c.Transpiration
d.Osmosis

Answer

a.

Explanation

  • The synthesis of carbohydrate food materials, mainly through the process of photosynthesis, occurs in green cells of plant. The non-green cells are therefore, dependent on photosynthetic cells for their carbohydrate supply. The organic food mainly from the leaves is transported to the non-green parts where it is needed for respiration and biosynthesis. “This movement of organic food or solute in soluble form, from one organ to another organ is called translocation of organic solutes. “
  • It has been now well established that carbohydrates are translocated from leaves to roots and storage organs (tubers, bulbs, fruits, etc. ) along the phloem in the form of sucrose. They are transported through living sieve elements of phloem (chiefly sieve tube members in seed plants). The process of translocation requires expenditure of metabolic energy and the solute moves at the rate of 100 cm/hr.

Directions of translocation

  • Downward translocation: It is of most important type, i. e. , from leaves to stem and roots.
  • Upward translocation: From leaves to developing flowers, buds, fruits and during germination of seeds and tubers, etc.
  • Radial translocation: From pith to cortex and epidermis.

Thus, we find that the translocation of food takes place from organs where food is in high concentrations (e. g. , leaf, tuber, and rhizome) to organs where it is in low concentration (e. g. , roots). The first are called supply ends and the later as consumption ends

Directions of translocation

Directions of Translocation

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