Exploring tiny life forms

In the past, scientists could only observe the world around them with the naked eye. They could not see anything out of the human range of vision.

However, around the year 1700, the Dutch scientist Anton Van Leeuwenhoek changed science forever. He was able to examine a drop of water using a simple microscope, which was basically a powerful magnifying glass. Van Leeuwenhoek discovered a new world, full of tiny creatures.

Using his microscope, Van Leeuwenhoek observed and drew pictures of cells and many microorganisms, including bacteria. This made him the ‘Father of Microbiology’.

Cells are the basic units of life. All living things are made up of cells. Most cells are very small and can only be seen through a microscope.

Cells are living units and they carry out the three basic life processes: 

• Nutrition. Cells obtain nutrients and energy from food.
• Reproduction. Cells can divide and produce new cells that are identical to themselves.
• Sensitivity. Cells react to what they perceive around them.

In addition, cells can specialize to perform a particular function.
Depending on the number of cells, living things can be classified into:

• Unicellular. Living things made up of a single cell.
• Multicellular. Living things made up of many cells.

The parts of a cell

Cells have three main parts: the membrane, the nucleus and the cytoplasm.

• Membrane. This is the covering around the cell.
• Nucleus. This is the part that controls the function of the cell.
• Cytoplasm. This is a jelly-like material, composed mainly of water, between the nucleus and the membrane. It contains the organelles, which carry out different functions of the cell.

Animal and plant cells

All animal and plant cells have a membrane, a nucleus and a cytoplasm with organelles. However, animal and plant cells are different in the following ways: 

• Plant cells have a rigid cell wall around the membrane. That is why the stems and branches of some plants are so hard.
• Plant cells have specialized organelles called chloroplasts that absorb sunlight, which plants need to make their food.
• Plant cells are usually bigger than animal cells and have a regular shape. Animal cells can be many different shapes.

Multicellular living things are made up of many different types of cells. These cells work together at different levels, called levels of organization.

Tissues

Groups of the same type of cells join together to form tissues. Animals have muscle tissue, which consists of muscle cells. Plants have an epidermis – the tissue that covers leaves – which consists of epidermal cells.

Systems

Organs are organized to form systems. Organs in systems work together to perform a common function. For example, the muscular system makes our body move, and the digestive system enables our body to obtain the nutrients we need to live.

The microscope and its parts

A microscope is an instrument with a combination of lenses. It makes very small living things or objects appear much larger than they really are.

Cells, as well as some other living things, are so small that we cannot see them with the naked eye. However, we can observe them through a microscope.