It is the time duration required for the Sun to orbit once around the centre of the Milky way galaxy. It takes 250 million years to do that.

The drugs which cause loss of sensation are called anaesthetics. They are given to patients when they undergo surgery.
There are two types.
i) General anaesthetics ii) Local anaesthetics

Four valence electrons termed as tetravalency.

Small intestine comprises of three parts.
i) Duodenum
ii) Jejunum
iii) Ileum
Ileum contain minute finger like projection called villi. It is one millimetre in length. Absorption of food takes place here. In this way digested food is absorbed by ileum.

Xylem is composed of
(a) Xylem tracheids
(b) Xylem fibres
(c) Xylem vessels
(d) Xylem parenchyma
Phloem is composed of
(a) Sieve elements
(b) Companion cells.
(c) Phloem fibres
(d) Phloem parenchyma

The number of magnetic field lines crossing unit area kept normal to the direction of field lines is called magnetic flux density. Its unit is Wb/m².

Electric field is the region around a charged body within which its influence can be experienced (i.e) within which it can attract or repel another charged body.

Mass of water = 25 grams
\(\triangle\)T = (100^oC - 0^oC) =100^oC
C = 4.18 J/g^oC
Heat energy required Q = M x C x \(\triangle\)T
= 25 x 4.18 x 100^oC
= 10450 j

Due to the presence of two layers in the body wall of coelenterates. So they are called as diploplastic animals.

Salt is used as preservative in food because,
1. Addition of salt removes the moisture content by the process of osmosis.
2. Prevents the growth of bacteria and reduces the activity of microbial enzymes.

Positive Geotropism
Positive Hydrotropism

\({ }_{1} \mu_{2}=\frac{\sin i}{\sin r}=\frac{\sin 45^{\circ}}{\sin 30^{\circ}}=\frac{1 / \sqrt{2}}{1 / 2}=\sqrt{2}=1.414\)

Since the particles in gases are far apart there is a lot of space between them. Therefore they can be forced to get closer or compressed when the volume decreases the pressure increases.

A standard unit is defined as a specific magnitude of a physical quantity that has been adopted by law or convention.