Biology idea 1: The cell
Cells are the basic building blocks of life. It is hard for us now to imagine scientists not knowing about cells, but until microscopes were developed, they couldn’t be seen, let alone described or observed.
Microscope
The invention of the microscope allowed us to view an invisible world – the objects around us that are too small to be seen with the naked eye.
Technology and scientific discovery
The invention of the microscope in the early 17th century was key to the discovery of cells and to distinguishing different types of cells. Explore this further in History of microscopy – timeline.
Organisms and cells
As people began to see cells in every living thing they observed, they started to think that all living things were made of these amazing functional units, called cells. Cell theory was formed.
Cell theory: What is it?
What does 'cell theory' really mean?
Plant cells and unicellular organisms had been observed in the 17th century, but another century was passing before they would be seen in animals. From about 1830 onwards, cell theory was developing - cells are the basic unit of life, and all living organisms are made up of them.
In fact, all life forms are built from cells. Bacteria consist of just a single cell, whereas our bodies are made up of approximately 75 trillion cells, divided into more than 200 different cell types.
Cell structure
Cells are complex and contain specialised structures to permit them to carry out a wide variety of functions.
Cell theory: Why is it important?
Nobel prize winner, Sir Paul Nurse, thinks there are five big ideas in biology. He suggests that cell theory is the first of these. During a 2006 tour of New Zealand, he explained why cells are so important.
Basic cells have an outer surface or plasma membrane, are filled with a substance called cytoplasm and contain organelles (“little organs”) that carry out specific functions depending on the cell type.
Bacteria cells are called prokaryotic, and their DNA is just floating around inside them. Find out more about what bacteria are. Plant and animal cells are called eukaryotic, and their DNA is contained within a specialised structure known as the nucleus.
Cell reproduction
Cells are able to create copies of themselves by a process called mitosis. The division of a cell from one, to two, to four forms the basis of growth and development of all living things.
