The Cellular Theory

1.1 - Introduction to the Cells

Andrew Allot, David Mindorff, José Azcue

IB Diploma Programme from Oxford - Biology

The Cellular Theory:

The internal structure of the living organisms is very intricate and consists of individual parts. Organs like the kidneys or the eyes are visibles, but if we dissect them, we can see different tissues and its structure. In the XVII century the biologists started to examine the tissues of the plants and the animals using microscopes, seeing that most of the structures looked similar (or practically the same), they decided to create the cellular theory: This theory states that all living organisms are constituted by cells. The organisms constituted by one cell are called unicellulars, and the ones that are constituted by more than one cells are called multicellulars.

3 Basic Principles of the Cellular Theory:

• All living beings are formed by cells.

Unicellular = 1 cell

Multicellular = +1 cells

• The cells are the smallest units with their own life.

There are diverse organelles that develop the cellular functions.

This organelles do not survive outside the cell.

• The cells proceed by division of other cells.

Division types

• Binary fission in prokaryotes
• Mitosis and meiosis in eukaryotes

        All cells always descent of existent cells

Development of the Cellular Theory (Authors):

1666 - Robert Hooke | Creation of the first microscope

1675 - Antonie Van Leeuwenhoek | Discovery of the protists, bacteria and animalcule

1838 - Matthias J. Scheiden and Theodor Schwann | First two principles of the cellular theory

1855 - Rudolf Virchow | Third principle of the cellular theory

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