General Biology 1 SHS
Week 1
Lesson 1. The Cell Theory
Cells are the basic building blocks of all living things. The human body is
composed of trillions of cells. They provide structure for the body, take in nutrients from
food, convert those nutrients into energy, and carry out specialized functions. Cells also
contain the body’s hereditary material and can make copies of themselves. Cells have
many parts, each with a different function. Some of these parts, called organelles, are
specialized structures that perform certain tasks within the cell. In this lesson, you are to
explain the postulates of the cell theory. The three postulates of the cell theory offer the
basis on how an organism is considered as a living thing.
Prior to the invention of the very first microscope, everything that could not be
seen by the naked eye was unexplainable. In 1665, English physicist Robert Hooke
used of the first light microscopes to look at thin slices of plant tissues. One of these, a
slice of cork, especially caught his eye. Under the microscope, cork seemed to be made
of thousands of tiny chambers. Hooke called this chambers ―cells‖ because they
reminded him of a monastery‘s tiny rooms, which were also known as cells. Until 1676,
Anton van Leeuwenhoek published his observations on tiny living organisms which he
named animalcules. It was believed that Leeuwenhoek was the first to observe under
his microscope the structure of a red blood cell of different animals as well as a sperm
cell. One of the leading botanists in his time, Robert Brown in 1831 was able to
compare diverse kinds of plant specimens under the microscope. He markedly indicated
that there is a common thing about them-they are all composed of cells, and inside the
cell is a dark dense spot which he termed as the nucleus. A few years later, German
botanist Matthias Schleiden (1838) concluded that all plant parts are made of cells.
Theodor Schwann (1839), also a botanist and a close friend of Schleiden, stated that all
animal tissues are composed of cells, too. In 1858, Rudolf Virchow concluded that all
cells come from pre-existing cells.
The discoveries made by Hooke, Leeuwenhoek, Schleiden, Schwann, Virchow,
and others led to the formulation of the cell theory. The cell theory describes the
properties of all cells. This theory can be summed up into three basic components: (1)
all living things are composed of one or more cells; (2) the cell is the basic unit of life;
and (3) all cells arise from pre-existing cells. Now, that you have an understanding of
the history of the cell theory, answer the activity that follows. What’s More A. The
Discovery of Cell Matthias Schleiden Robert Hooke Theodor Schwann Anton van
Leeuwenhoek Rudolf Virchow
Activity 1. Research on the ―Cell Theory which tells about the discovery of cell. Take
note of the scientists and their respective works.
Matthias Schleiden, Robert Hooke, Theodor Schwann , Anton van Leeuwenhoek,
Rudolf Virchow
Choose from above which scientist gave the following statements.
__________1. All cells come from pre-existing cells (1858).
__________2. All animals are made up of cells (1839).
__________3. All plants are made up of cells (1838).
__________4. Tiny living organisms are observed (1676).
__________5. Thousands of tiny empty chambers in cork are called cells (1665).
Activity 2: Answer the following questions on a separate sheet of paper.
1.What is the cell theory and what does it state?
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