Q11 of 40 Page 1

Reproduction is one of the most important characteristics of living beings. Give three reasons in support of the statement.

Reproduction helps in increasing the number of members of a population. It replaces the dead members with new ones thus minimizing the extinction of a particular species. It brings variations in a species thus leading to evolution.


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9

Write the number of periods and groups in the Modern Periodic Table. How does the metallic character of elements vary on moving (i) from left to right in a period, and (ii) down a group? Give a reason to justify your answer.

 10

Na, Mg, and Al are the elements of the 3rd period of the Modern Periodic Table having group number 1, 2 and 13 respectively. Which one of these elements has the (a) highest valency, (b) largest atomic radius, and (c) maximum chemical reactivity? Justify your answer stating the reason for each.

 12

What is vegetative propagation? State two advantages and two disadvantages of this method.

 13

List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males ? How does the use of these techniques have a direct impact on the health and prosperity of a family?