• 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.

Dogma-A statement or an interpretation declared as authoritative with the expectation that it would be followed without question.

Bigot- An individual who is intolerant of another person's religious beliefs or culture.

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.

A chronicle is a historical account of facts and events arranged in chronological order. A chronicle contains important historical events and generally are without any analysis and interpretation.