Diffusion is the process of movement of molecules under a concentration gradient. It is an important process occurring in all living beings. Diffusion helps in the movement of substances in and out of the cells. The molecules move from a region of higher concentration to a region of lower concentration until the concentration becomes equal throughout.

A tissue is defined as a cluster of cells which are similar in structure and work together to perform a particular function.

Sclerenchyma tissue makes up the husk of coconut.

The constituents of phloem are  Sieve tubes, Companion cells, Phloem parenchyma,  Phloem fibres.

Leucoplasts are the non-pigmented plastids that are colourless.

The Aluminium electron configuration will be 1s²2s²2p⁶3s²3p¹.

(i) The Central Highland: The Peninsular Plateau consists of the broad divisions the Central Highlands and the Deccan Plateau. The part of the Peninsular plateau to the north of the Narmada river covers a major area of the Malwa plateau is known as the Central Highlands. The Vindhyas range is bounded by the Central Highlands on the south and the Aravalis on the northwest. The further westward extension gradually merges with the sandy and rocky desert of Rajasthan. The flow of the rivers draining this region, namely the Chambal, the Sind, the Betwa and Ken is from southwest to northeast, thus indicating the slope. The Central Highlands are wider in the west but narrower in the east. The eastward extensions of this plateau are locally known as the Bundelkhand and Baghelkhand.

(ii) The Island Groups of India: India has two island groups - the Lakshadweep Islands and the Andaman and Nicobar Islands. The Lakshadweep Islands group lies close to the Malabar coast of Kerala. This group of islands is composed of small coral islands. Earlier they were known as Laccadive, Minicoy and Amindive. In 1973, these were named as Lakshadweep. It covers small area of 32 sq km. Kavaratti Island is the administrative headquarters of Lakshadweep. The Andaman and Nicobar Islands are located in the Bay of Bengal. They are bigger in size and are more numerous and scattered. The entire group of islands is divided into two broad categories - the Andaman in the north and the Nicobar in the south. These island groups are of great strategic importance for the country. They lie close to equator and experience equatorial climate and has thick forest cover.

Let us consider an object of mass m, moving along a straight line with an initial velocity u. Let us say, after a certain time t, with a constant acceleration, the final velocity becomes v. Here we see that, the initial momentum
The final momentum

The change in momentum can be written as

As we know, the rate of change of momentum with respect to time is proportional to the applied force. The applied force

Or,

as acceleration (a) = rate of change of velocity with respect to time.

Above is the second law of motion formula.

• m = 1000kg
• a = 4.00m/sec^2

We know that

F = m × a

By putting given values in above formula we get,

So the net force is required to accelerate a 1000 kg car at 4.00 m/s2 is 4000 N.

The movement of water molecule from a region of higher concentration to a region of its lower concentration through a semi permeable membrane is called Osmosis.

1. General method:

They involve (a) Preventing exposure against microbes (b) By boosting the immune system

(a) Preventing exposure against microbes can be done in the following ways:

For air-born microbes we can prevent exposure by avoiding overcrowded places. For water-borne microbes we can prevent exposure by not using contaminated water.

For vector-borne infections we can prevent exposure by providing a clean environment.

(b) By boosting the immune system:

Our immune system plays an important role in fighting against the microbes that enter our body. strengthening the immune system can help in preventing many diseases. 

So, proper nourishment or healthy diet that includes all the necessary nutrients as well as vitamins and minerals is necessary for better functioning of our immune system.

2. Specific method
It involves the prevention method directed against a particular disease.

It is done by immunisation which is the process of introducing a weakened pathogen inside the body of the host to make his/her immune system to produce antibodies against that particular disease so that the next time even if the disease will strike the host’s body with full vigor, the body will be able to protect itself with the help of these antibodies.

• Acute diseases refer to the medical condition that occurs suddenly and lasts for a shorter period of time.

• Chronic diseases develop slowly and last for a lifetime.

• Chronic diseases are sometimes fatal.

• Acute diseases when persist for a longer time can term fatal, otherwise can be treated by certain medications.

• Common cold, typhoid, jaundice, cholera, burn, are some of the acute diseases.

• Chronic diseases include AIDS, elephantiasis, cancer, tuberculosis etc.

Functions of the Epithelium

Epithelia tissue forms boundaries between different environments, and nearly all substances must pass through the epithelium. In its role as an interface tissue, epithelium accomplishes many functions, including:

1. Protection for the underlying tissues from radiation, desiccation, toxins, and physical trauma.
2. Absorption of substances in the digestive tract lining with distinct modifications.
3. Regulation and excretion of chemicals between the underlying tissues and the body cavity.
4. The secretion of hormones into the blood vascular system. The secretion of sweat, mucus, enzymes, and other products that are delivered by ducts come from the glandular epithelium.
5. The detection of sensation.

Types of Epithelial cells:

Simple Epithelia

Simple epithelium consists of a single layer of cells. They are typically where absorption, secretion  and filtration occur. The thinness of the epithelial barrier facilitates these processes.

Simple epithelial tissues are generally classified by the shape of their cells. The four major classes of simple epithelium are: 1) simple squamous; 2) simple cuboidal; 3) simple columnar; and 4) pseudostratified.

Simple Squamous

Simple squamous epithelium cells are flat in shape and arranged in a single layer. This single layer is thin enough to form a membrane that compounds can move through via passive diffusion. This epithelial type is found in the walls of capillaries, linings of the pericardium, and the linings of the alveoli of the lungs.

Simple Cuboidal

Simple cuboidal epithelium consists of a single layer cells that are as tall as they are wide. The important functions of the simple cuboidal epithelium are secretion and absorption. This epithelial type is found in the small collecting ducts of the kidneys, pancreas, and salivary glands.

Simple Columnar

Simple columnar epithelium is a single row of tall, closely packed cells, aligned in a row. These cells are found in areas with high secretory function (such as the wall of the stomach), or absorptive areas (as in small intestine ). They possess cellular extensions (e.g., microvilli in the small intestine, or the cilia found almost exclusively in the female reproductive tract).

Pseudostratified

These are simple columnar epithelial cells whose nuclei appear at different heights, giving the misleading (hence pseudo) impression that the epithelium is stratified when the cells are viewed in cross section.

Pseudostratified epithelium can also possess fine hair-like extensions of their apical (luminal) membrane called cilia. In this case, the epithelium is described as ciliated pseudostratified epithelium. Ciliated epithelium is found in the airways (nose, bronchi), but is also found in the uterus and fallopian tubes of females, where the cilia propel the ovum to the uterus.

Stratified Epithelium

Stratified epithelium differs from simple epithelium by being multilayered. It is therefore found where body linings have to withstand mechanical or chemical insults.

Stratified epithelia are more durable and protection is one their major functions. Since stratified epithelium consists of two or more layers, the basal cells divide and push towards the apex, and in the process flatten the apical cells.

Epithelial cells are numerous, exist in close apposition to each other, and form specialized junctions to create a barrier between connective tissues and free surfaces. Free surfaces of the body include the outer surface of internal organs, lining of body cavities, exterior surface of the body, tubes and ducts.They perform a variety of functions that include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception.

Types of Epithelial cells:

Simple Epithelia

Simple epithelium consists of a single layer of cells. They are typically where absorption, secretion  and filtration occur. The thinness of the epithelial barrier facilitates these processes.

Simple epithelial tissues are generally classified by the shape of their cells. The four major classes of simple epithelium are: 1) simple squamous; 2) simple cuboidal; 3) simple columnar; and 4) pseudostratified.

Simple Squamous

Simple squamous epithelium cells are flat in shape and arranged in a single layer. This single layer is thin enough to form a membrane that compounds can move through via passive diffusion. This epithelial type is found in the walls of capillaries, linings of the pericardium, and the linings of the alveoli of the lungs.

Simple Cuboidal

Simple cuboidal epithelium consists of a single layer cells that are as tall as they are wide. The important functions of the simple cuboidal epithelium are secretion and absorption. This epithelial type is found in the small collecting ducts of the kidneys, pancreas, and salivary glands.

Simple Columnar

Simple columnar epithelium is a single row of tall, closely packed cells, aligned in a row. These cells are found in areas with high secretory function (such as the wall of the stomach), or absorptive areas (as in small intestine ). They possess cellular extensions (e.g., microvilli in the small intestine, or the cilia found almost exclusively in the female reproductive tract).

Pseudostratified

These are simple columnar epithelial cells whose nuclei appear at different heights, giving the misleading (hence pseudo) impression that the epithelium is stratified when the cells are viewed in cross section.

Pseudostratified epithelium can also possess fine hair-like extensions of their apical (luminal) membrane called cilia. In this case, the epithelium is described as ciliated pseudostratified epithelium. Ciliated epithelium is found in the airways (nose, bronchi), but is also found in the uterus and fallopian tubes of females, where the cilia propel the ovum to the uterus.

Stratified Epithelium

Stratified epithelium differs from simple epithelium by being multilayered. It is therefore found where body linings have to withstand mechanical or chemical insults.

Stratified epithelia are more durable and protection is one their major functions. Since stratified epithelium consists of two or more layers, the basal cells divide and push towards the apex, and in the process flatten the apical cells.

Connective tissues, as the name implies, support and connect different tissues and organs of the body. They are widely distributed in every part of the body. They originate from the mesoderm (the middle germinal layer of the embryo).

Connective tissues are divided into three groups:

• Loose Connective Tissue
• Dense Connective Tissue
• Specialised Connective Tissue