IGCSE Biology Paper-1: Specimen Questions with Answers 157 - 158 of 208

Question 157

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Question

MCQ▾

The diagram shows a section through an eye.

Entire Front of Eye

Entire Front of Eye

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What are the X and Y?

Choices

Choice (4)
a.Cornea and Iris
b.Lens and Cornea
c.Cornea and lens
d.Iris and Cornea

Answer

c.

Explanation

Our eye is a slightly asymmetrical globe, about an inch in diameter. The front part includes:

  • Iris: the colored part
  • Cornea: a clear dome over the iris
  • Pupil: the black circular opening in the iris that lets light in
  • Sclera: the white of your eye
  • Conjunctiva: a thin layer of tissue that covers the entire front of your eye, except for the cornea
Entire Front of Eye

Entire Front of Eye

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Question 158

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Question

MCQ▾

What is a function of phloem?

Choices

Choice (4)
a.storage of food
b.transpiration
c.translocation
d.support

Answer

c.

Explanation

  • The synthesis of carbohydrate food materials, 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 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 .

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, rhizome) to organs where it is in low concentration (e. g. , roots). The first are called supply ends and the later as consumption ends.

Transpiration of Water

Transpiration of Water

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