Assumption College Primary Section

Semester 2 / 2010

MicroscopeEyepieceFocusing knobCoarse focusFine focusSpecimenUnicellularMulti-cellularSlidestage

ParameciumBacteriaAmoebaCell membraneCell wallCytoplasmNucleusVacuolesCell

ChloroplastChlorophyllSpherical structureCharacteristicsGenerationCellulose

British scientist Robert Hooke discovered an instrument which helped him see very small objects. This instrument is called a microscope.

He saw a slice of a piece of cork underhis microscope and discovered that it was made up of a number of smallboxes. He gave the name ‘cells’ to these boxes.

Cells are like building blocks that make up the bodies of living things. We can saythat a cell is a single unit of life.

Since then much more powerful microscopes have been made and scientistshave examined different types of living things with them.

They have found that all living things are made up of cells.

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The microscope has two main lenses, the objective lenses and the eyepiece lenses.It has an arrangement for lighting the specimen being examined. The focusing knob is used to focus the image of the specimen – that is, to make the image sharp and clear.The specimen to be seen is placed on a glass slide with a drop of fluid.The slide is covered with a glass cover slip.The prepared slide is placed on the viewing stageof the microscope. It is viewed from the eyepiece.

The plants and animals that you can seearound you are made up of a large number of cells. They are called multi-cellularliving things.

A human body has several billion cells.It has many types of cells. Each cell has particular job to perform.

Red blood cells carry oxygen to differentparts of the body.

There also exists a large number of living things around you that are made up of only one cell. They are called unicellular living things. They are too tiny to be seen with the naked eye. You can only see them under a microscope.

Cells are of different shapes and sizes.Bacterial cells are the smallest.The largest cell is the egg of an ostrich. It is a single cell.

The cells in multi-cellular living thingsare different shapes and sizes, depending onthe work they do. The longest cells in our body are the nerve cells that carry messages to and from theBrain. They run from head to toe.

Skin cells are flat. They join together to form a protective layer on our body.