Lignin is a class of complex organic polymers that form important structural materials in the support tissues of vascular plants and some algae.

{tex}C_9H_{10}O_2,C_{10}H_{12}O_3,C_{11}H_{14}O_4{/tex}

Hydra belongs to Colentereta and sea anemone belongs to Cnidaria

plant cell

A colloid is a solution that has particles ranging between 1 and 1000 nanometers in diameter, yet are still able to remain evenly distributed throughout the solution.

A sol is a colloidal suspension of very small solid particles in a continuous liquid medium. Sols are quite stable and show the Tyndall effect. Examples include blood, pigmented ink, cell fluids and paint. Artificial sols may be prepared by dispersion or condensation.

It is a property due to which it resist (remain unchanged) the change of its state of rest or motion is called inertia. Inertia depend on a mass .

E.G.: When a tree is shaken. its fruits and leaves falls down because due to inertia fruits and leaves tend to remain at rest due to their inertia.

      When a bus suddenly stop then passenger fall forward. This is due to inertia passenger is moving with high speed as bus is moving. When bus suddenly stop then passenger remain to tend in a motion hence fall forward. 

The natural tendency of objects to resist a change in their state of rest or of uniform motion is called inertia. The mass of an object is a measure of its inertia. Higher the mass, the higher is the inertia. E.g. When an unbalanced force is applied by the engine to change the direction of motion of a vehicle, we tend to slip to one side of the seat due to the inertia of our body.

Those nutrients that are needed in large amounts are called macronutrients.

There are three macronutrients required by human beings - carbohydrates (sugar), lipids (fats), and proteins. Each of these macronutrients provides energy in the form of calories.

The soil supplies nitrogen, phosphorus, potassium, calcium, magnesium, and sulphur In relatively large amounts to plants. These are the macronutrients for plants.

In relatively small amounts, the soil supplies iron,manganese, boron, molybdenum, copper, zinc, chlorine, and cobalt, the so-called micronutrients.

A plant uses these nutrients to support its growth, life cycle, and biological functions.

Tissues that consist of cells with thin cellulose walls and continuously dividing cells are called meristematic tissues. Cells of meristematic tissues differentiate (i.e. lose the ability to divide and assume definite shape and size, and a specific function) to form permanent tissues.

Robert Boyle was the first scientist to use the term element in 1661.

Antoine Laurent Lavoisier, a French chemist, was the first to establish an experimentally useful definition of an element. He defined an element as a basic form of matter that cannot be broken down into simpler substances by chemical reactions.

Robert Boyle was the first scientist to use the term element in 1661. Antoine Laurent Lavoisier, a French chemist, was the first to establish an experimentally useful
definition of an element. He defined an element as a basic form of matter that cannot be broken down into simpler substances by chemical reactions.

Collenchyma is a cell and tissue type in which the primary walls are unevenly thickened and consist of homogeneous, more or less elongated living cells; it provides mechanical support to the plant organs where present.

Epithelial Tissue

There are three principal classifications associated with epithelial cells. Squamous epithelium has cells that are wider than they are tall. Cuboidal epithelium has cells whose height and width are approximately the same. Columnar epithelium has cells taller than they are wide.
This illustration shows the three principal classifications associated with epithelial cells. Squamous epithelium has cells that are wider than they are tall. Cuboidal epithelium has cells whose height and width are approximately the same. Columnar epithelium has cells taller than they are wide. There are pictures of each of these types of epithelium: simple squamous, simple cuboidal, simple columnar, stratified squamous, stratified cuboidal, pseudostratifed columnar, and transitional.

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.  

Stratified epithelia can be columnar, cuboidal, or squamous type. However, it can also have the following specializations:

Keratinized Epithelia

In keratinized epithelia, the most apical layers (exterior) of cells are dead and lose their nucleus and cytoplasm. They contain a tough, resistant protein called keratin. This specialization makes the epithelium waterproof, and it is abundant in mammalian skin. The lining of the esophagus is an example of a non-keratinized or moist stratified epithelium.

Transitional Epithelia 

Transitional epithelia are found in tissues that stretch and it can appear to be stratified cuboidal when the tissue is not stretched, or stratified squamous when the organ is distended and the tissue stretches. It is sometimes called the urothelium since it is almost exclusively found in the bladder, ureters, and urethra.

Some elements, such as gold, silver, iron and carbon have been known since ancient times; it is not possible to credit a single person for their discovery. Different elements have been discovered by different scientists.

3 Newton is a net force (a push or a pull) whose magnitude is 3 N.

A body of mass 3 kg moving with an acceleration of 1 m.s^-1 will produce a force of 3 N. (F = Mass times Accleration)

A body of mass 1 kg moving with an acceleration of 3 m.s^-1 will also produce a force of 3 N.

A body of mass 1.5 kg moving with an acceleration of 2 m.s^-1 will also produce a force of 3 N.

A body of mass 2 kg moving with an acceleration of 1.5 m.s^-1 will also produce a force of 3 N.

1. Chromoplasts are a type of plastids present in the cytoplasm of the plant cells.

2. They are found in fruits, flowers, roots, and stressed and aging leaves, and are responsible for their distinctive colors.

1. Valence electrons are the electrons located at the outermost shell of an atom.

2. For example: oxygen has 8 electrons & electronic configuration of oxygen is 2, 6. Therefore, oxygen has 6 valence electrons.

3. Similarly, Neon's outermost shell has 8 electrons, therefore has 8 valence electrons.