Describe the difference between prokaryotic and eukaryotic cells. Describe the theory of endosymbiosis and the evidence for and against this theory.

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Describe the difference between prokaryotic and eukaryotic cells. Describe the theory of endosymbiosis and the evidence for and against this theory.

All living organisms are made up of cells. The cells can be divided into two groups: prokaryotic and eukaryotic. Prokaryotes date back to 3,500 million years ago, whilst eukaryotes are only as old as 1,500 million years. As prokaryotes come before eukaryotes, they are much simpler. Eukaryotes have become more developed and complex since prokaryotes.

The two types of cells have similarities as well as differences. The similarities are that they both have a cell surface membrane, cytoplasm, DNA and ribosomes. However, even these similarities are in their own way, slightly different. For example, both cells contain DNA, but the structure of the DNA differs (explained later in more detail). As you will read below, eukaryotes are much more complex and contain many more organelles than the prokaryotes.

Size

Prokaryotes are usually much smaller than eukaryotes. Its average size ranges from 1 to 10 µm, whilst the eukaryotic cell is typically 10 to 150 µm. This actually gives prokaryotes a large surface-to-volume ratio, making it a simple, but efficient organism (absorbed nutrients have to