The small intestine's main function is to absorb nutrients from the food we eat.

Villi helps to increase the surface area of the intestine for absorbtion.

Villi also contains vessels called lacteals.

The process of absorption means that a substance captures and transforms energy. The absorbent distributes the material it captures throughout whole and adsorbent only distributes it through the surface. The process of gas or liquid which penetrate into the body of adsorbent is commonly known as absorption.

• Plants are capable of making their food themselves but humans and animals cannot.
• Carbohydrates, proteins, fats, vitamins and minerals are essential components of food, these components are called nutrients.

Amino Acids are the organic compounds which combine to form proteins, hence they are referred to as the building components of proteins. These biomolecules are involved in several biological and chemical functions in a human body and are the necessary ingredients for the growth and development of human beings. There are about 300 amino acids which occur in nature.

Amino acids contain the basic amino groups (-NH2) and carboxyl groups (-COOH). The ingredients present in proteins are of amino acids. Both peptides and proteins are the long chains of amino acids. Altogether, there are twenty amino acids, which are involved in the construction of proteins.

Glycerol is a sweet, syrupy fluid substance obtained from animal fats and oils or by the fermentation of glucose. It is used as a solvent, sweetener, and antifreeze and in making explosives and soaps. Glycerol consists of a propane molecule attached to three hydroxyl (OH) groups. Also called glycerin, glycerine.

Omega-3 fatty acids are polyunsaturated fatty acids which have a double bond (C=C) at the third carbon atom from the end of the carbon chain. It is a group of fatty acids which have the first unsaturated bond in the third position from the omega carbon.

Omega 3 Fatty Acids are believed to prevent insulin resistance, reduce serum triglycerides, prolong bleeding times, improve lipid profile, decrease platelet adhesiveness, and reduce platelet counts.

Animals and humans are called heterotrophs because they do not manufacture their own food like green plants, they depend on other organisms for food.

• Organisms show variety in Cell Number, Shape and Size:

There are millions of living organisms having variety in shapes and sizes. Their organs also show variety in shapes and sizes and also the number of cells in them.

1. Numbers of cells – All living organisms are made up of cells but the number of cells varies from organism to organism. Some organisms are made up of just one cell and are called unicellular organisms. Example – Amoeba, Paramecium, Euglena, bacteria, etc. Some organisms are made up of more than one cell or many cells are called multicellular organisms. Example – plants, animals, etc. The number of cells less or more, does not affect the functioning in the body of any organism. A single-celled organism performs all the necessary functions that multicellular organisms perform. A single-celled organism, like amoeba, captures and digests food, respires, excretes, grows and reproduces. Similar functions in multicellular organisms are carried out by groups of specialised cells forming tissues which group together to form organs.
2. Shape of cells – There are many types of cells in the bodies of multicellular organisms which differ in shapes. Example – an amoeba appears irregular in shape and a nerve cell is long and branched whereas a muscle cell is pointed at both ends and has a spindle shape.
3. Size of cells – The cells are of many different sizes. Most of the cells are extremely small in size and hence cannot be seen with the naked eyes. The smallest cell is 0.1 to 0.5 micrometre in bacteria.  The largest cell measuring 170 mm ×130 mm, is the egg of an ostrich. The size of the cell is related to its function. For example, nerve cells, both in the elephant and rat, are long and branched. They perform the function of transferring messages.

Oesophagus

• Oesophagus is also called the food pipe.
• It runs along the neck and the chest.
• The food from mouth after swallowing passes into oesophagus and is pushed down to stomach by a special movement called peristalsis.
• This peristaltic movement takes place through out the alimentary canal which pushes the food in downwards direction.
• At some times the stomach is not ready to take up food causing vomiting, where food is expelled out from the oesophagus to mouth by reverse peristaltic movement.

Plane mirrors and convex mirrors only produce virtual images. Only a concave mirror is capable of producing a real image and this only occurs if the object is located a distance greater than a focal length from the mirror's surface. 10. The image of an object is found to be upright and reduced in size. The best example of a virtual image is your reflection in the mirror. Real images are produced by intersecting rays while virtual images are produced by diverging rays. Real images can be projected on a screen while virtual ones cannot. Real images are formed by two opposite lens, concave and convex.

The land gets heated up by the heat radiated by the sun, much faster than the water during daytime. This heats up the air over the land and it expands and hence the hot air rises up and creates a vacuum. The cool air from the sea occupies the space left by the hot air. The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called the sea breeze.

But the reverse process takes place at night. The land cools down quickly and sea water remains hot. This heats up the air over the sea and it expands and hence the hot air rises up and creates a vacuum. The cool air from the land occupies the space left by the hot air. And hence the cool air moves from the land to the sea and is known as the land breeze.

• Anything that can be seen and touched is called an object.
• Anything which has mass and occupies space is called matter.
• The sorting of objects into groups with each group having its own characteristic properties is called classification of objects.

Insectivorous Plants: Those green plants which obtain their food partly from insects are called insectivorous plants. These plants have specialized leaves to catch the insects. They are also called as carnivorous plants. For e.g. Pitcher plant, Sundew plant, venus fly-trap plant etc. 

The insectivorous plants grow in soil which do not contain sufficient nitrogen mineral. These plants (e.g. pitcher plant) are green and carry out photosynthesis to obtain a part of the food required by them. So, insectivorous or carnivorous plants feed on insects to obtain the nitrogen needed for their growth.

Rhizobium carry out nitrogen fixation. In order for plants to get nitrogen it must first be incorporated into organic compounds such as amino acids in a process known as nitrogen fixation. The Rhizobia absorb nitrogen and use it to make proteins and as a by-product it produces nitrogen-containing ammonium which, unlike the N₂ in the air, the plant can take up and use for growth (protein production).
The relationship between legumes and Rhizobium is a form of symbiotic relationship, where both organisms benefit from each other - the plant gets nitrogen from the ammonium and the bacteria receive organic acids from the plant to use as food source.

A vessel element or vessel member (trachea) is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements (tracheae) are typically found in flowering plants(angiosperms) but absent from most gymnosperms such as conifers.

Vessel elements are the building blocks of vessels, which constitute the major part of the water transporting system in those plants in which they occur. Vessels form an efficient system for transporting water (including necessary minerals) from the root to the leaves and other parts of the plant.

Asexual reproduction spans a variety of methods. The simplest single-celled organisms such as archaea, and bacteria, reproduce by binary fission. In this process, the cells simply divide in half creating, a clone of the parent. This method also holds the benefit of being very quick and energy-efficient. For example, bacteria that reproduce by binary fission can give rise to progeny every few hours. Multiple fission also exists in which, an organism splits into more than one offspring. Certain species of algae and protozoans exhibit multiple fission.

Sexual reproduction is the combination of reproductive cells from two individuals to form a third unique offspring. Sexual reproduction produces offspring with a different combination of genes.

Electromagnet: The magnet made by using electric current is called an electromagnet. The electromagnet works on the magnetic effect of current. 

A simple electromagnet consisting of a coil of insulated wire wrapped around an iron core. A core of ferromagnetic material like iron serves to increase the magnetic field created.  The strength of magnetic field generated is proportional to the amount of current through the winding.

Take around 75 cm long piece of insulated   flexible wire and an iron nail.  Wind the wire tightly around the nail in the form of a coil. Connect the free ends of the wire to the terminals of a cell through a switch. Place some pins on or near the end of the nail. Now switch on the current and the pins cling to the tip of the nail.  Switch off the current. The coil in the above activity behaves like a magnet when electric current flows through it. When the electric current is switched off, the coil generally loses its magnetism. Such coils are called electromagnets. The electromagnets could be made strong by increasing the number of turns in the coil and by increasing the current passing through the coil.

These electromagnets are used in electric bells, loud speakers, electric motors, electric fans toys and telephone instruments. Electromagnets are also used in separating the non-magnetic and magnetic materials. It is used by doctors to remove tiny particles from the eyes of a person which may have fallen into the eyes accidentally.