Exercise

When $\mathrm{Mg}$ is burnt in the atmosphere of an element X, a yellow powder is obtained. When this is dissolved in water, it gives a compound Y with a pungent smell. What are X and Y? 

The table lists the development of few characteristics in the human body.

At which stage of human development do the above characteristics appear?

The table lists the development of few characteristics in the human body.

Which of these statements is true for the characteristics listed in the table above?

The diagram below represents the male human reproductive system.

Identify the part that is responsible for the secretion of testosterone.

In the diagram below, each labelled region (P to W) represents a certain combination of reproductive processes found in an animal. Each labelled region is characterised by the different circles that it is (or is not) a part of. 

Answer the following question based on this diagram. 

Name any one animal whose mode of reproduction is represented by region P. 

Bindu wants to produce a hybrid variety of tomatoes. She has tomato plants X and Y belonging to two different varieties, one with smooth, long fruits and the other one with wrinkled, round fruits. 
Tomatoes have bisexual flowers. Bindu carries out the following steps carefully to cross pollinate the flowers of plants X and Y: 
1. She removes a part of the flowers of tomato plant X just before the flowers bloom. 
2. She manually pollinates the flowers of tomato plant X using pollen from the flowers of tomato plant Y.
3. She ties small plastic bags around the pollinated flowers of tomato plant X. The plastic bags are removed after a couple of days. 

Bindu carried out step 1 so as to prevent self-pollination. Which part did she remove?

Plants produced through vegetative propagation are genetically identical to their parents. What could be the biggest disadvantage of vegetative propagation?

A piece of iron rusts when it comes in contact with air and moisture. Prakash had two identical shiny iron pieces $\mathrm{P}$ and $\mathrm{Q}$. To prevent the pieces from rusting, he coated piece $\mathrm{P}$ with oil paint and he galvanised piece $\mathrm{Q}$ with a coat of zinc metal. He noticed that the coatings were not complete and that a small part of the iron was exposed in both the pieces.

What is Prakash likely to observe about the exposed parts of the two iron pieces after some days? Explain why.