IGCSE Biology Paper-1: Specimen Questions with Answers 184 - 185 of 208

Question 184

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Question

MCQ▾

The diagram shows the four types of human tooth.

Human Tooth

Human Tooth

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Which teeth is/are not a part of milk teeth?

Choices

Choice (4)
a.incisor and premolar
b.premolar and molar
c.only premolar
d.only incisor

Answer

c.

Explanation

The milk teeth begin to appear around the age of 4 to 6 months and usually form a complete set of 20 milk teeth by 3 years of age.

These 20 teeth include:

  • 4 central incisors or front teeth for cutting and biting (two per jaw)
  • 4 lateral incisors (two per jaw)
  • 4 canines or cuspids for tearing (two per jaw)
  • 4 first molar teeth or back teeth for grinding and chewing (two per jaw)
  • 4 second molar teeth (two per jaw)
  • Premolars are Absent
  • 2 i/1 c/0 pm/2 m
The Heart Consists of Four Chambers

The Heart Consists of Four Chambers

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Question 185

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Question

MCQ▾

Which of the following shows the correct explanation of the given figures?

The Cell X, Y and Z

The Cell X, Y and Z

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Choices

Choice (4)
a.Cell “X” will gain H20, Cell “Y” will lose H20, Cell “Z” will neither gain nor lose H20.
b.Cell “X” will gain H20, Cell “Y” will neither gain nor lose H20, Cell “Z” will lose H20.
c.Cell “X” will neither gain nor lose H20, Cell “Y” will gain H20, Cell “Z” will lose H20.
d.Cell “X” will lose H20, Cell “Y” will gain H20, Cell “Z” will neither gain nor lose H20.

Answer

a.

Explanation

  • Plasmolysis (Gr. Plasma = something formed; lysis = loosing): If a living plant cell is placed in a highly concentrated solution (i. e. hypertonic solution), water comes out of the cell due to exosmosis, through the plasma membrane. The loss of water from the cell sap causes shrinkage of the protoplast away from the cell wall in the form of a round mass in the center. “The shrinkage of the protoplast of a living cell from its cell wall due to exosmosis under the influence of a hypertonic solution is called plasmolysis. ” The stage of plasmolysis, when the protoplast just begins to contract away from the cell wall is called incipient plasmolysis. The stage when the cell wall has reached its limit of contraction and the protoplast has detached from cell wall attaining spherical shape is called evident plasmolysis. In a plasmolysis cell, the space between the contracted protoplast and the cell wall remains filled with external solution. If a cell with incipient plasmolysis is placed in a hypertonic solution it will show more plasmolysis.
  • If a plasmolysis cell is placed in pure water or hypotonic solution, endosmosis takes place. The protoplast attains its original shape and the cell regains its original size. “The swelling up of a plasmolysis protoplast due to endosmosis under the influence of a hypotonic solution or water is called DE plasmolysis’. DE plasmolysis is possible only immediately after plasmolysis otherwise the cell protoplast becomes permanently damaged. Leaf of Tradescantia is used for demonstration of plasmolysis in laboratory. The value of TP becomes zero at the time of limiting plasmolysis and below zero during incipient and evident plasmolysis.
Flaccid, Turgid and Plasmolyzed

Flaccid, Turgid and Plasmolyzed

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