While examining a thin slice of cork, Robert Hooke saw that the cork resembled the structure of a honeycomb consisting of many little compartments. Cork is a substance which comes from the bark of a tree. This was in the year 1665 when Hooke made this chance observation through a self-designed microscope. Robert Hooke called these boxes cells. Cell is a Latin word for ‘a little room’. This may seem to be a very small and insignificant incident but it is very important in the history of science. This was the very first time that someone had observed that living things appear to consist of separate units. The use of the word ‘cell’ to describe these units is used till this day in biology. Let us find out about cells.

CHAPTER - 5

THE FUNDAMENTAL UNDAMENTAL UNIT OF LIFE

Compound microscope

A microscope (from the Ancient Greek: μικρός, mikrós, "small" and σκοπεῖν, skopeîn, "to look" or "see") is an instrument used to see objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using such an instrument. Microscopic means invisible to the eye unless aided by a microscope. There are many types of microscopes, and they may be grouped in different ways. One way is to describe the way the instruments interact with a sample to create images, either by sending a beam of light or electrons to a sample in its optical path, or by scanning across, and a short distance from the surface of a sample using a probe. The most common microscope (and the first to be invented) is the optical microscope, which uses light to pass through a sample to produce an image. Other major types of microscopes are the fluorescence microscope, the electron microscope (both the transmission electron microscope and the scanning electron microscope) and the various types of scanning probe microscopes.

MICROSCOPE

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Animal cell and its components

Close your eyes and picture a brick wall. What is the basic building block of that wall? A single brick, of course. Like a brick wall, your body is composed of basic building blocks, and the building blocks of your body are cells.

Fortunately, your cells are way more interesting than bricks. (Just as you, undoubtedly, are much more interesting than a brick wall!) Bricks are generally square-shaped, like all other bricks, while cells can have many shapes—round, square, spindle-shaped, and star-like. Bricks generally stay put, while many types of cells will happily migrate from one place to another. And if you slice a brick in half, you just find more brick, while if you slice a cell in half—which is a good trick, given how tiny they are—you’ll find an intricate and beautiful array of specialized structures that help the cell perform its function. Yes, cells are building blocks, but they’re the most amazing building blocks in the world!

Cells perform a huge number of different roles within your body. For example, epithelial cells protect the outside surface of the body as part of the skin and cover the organs and body cavities within. Bone cells build up bones to provide support for the body. Cells of the immune system fight invading bacteria. Blood and blood cells carry nutrients and oxygen throughout the body while removing carbon dioxide. Each of these cell types plays a vital role in the growth, development, and day-to-day maintenance of the body.

ANIMAL CELL

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