Video Transcript
Which of the following was not a
major event in the history of the development of cell theory? (A) Van Leeuwenhoek viewing living
cells from algae and protists under his microscope. (B) Schwann identifying that
bacteria and viruses were single-celled organisms. (C) Hooke viewing the remains of
cells in a slice of cork under a microscope. (D) Virchow determining that all
cells are produced by preexisting cells. (E) Schleiden concluding that all
plants are comprised of cells.
This question is asking us to
recall the major events of cell theory. Before getting into this, let’s
first review what cell theory is.
Cell theory is made up of three
principles, or postulates. The first is that all living things
are made up of at least one cell. The second is that the cell is the
basic unit of life. And the third principle of cell
theory is that all cells come from preexisting cells. Five well-known scientists are
responsible for generating this theory. Let’s discuss their discoveries in
order to answer our question correctly.
We can trace the first of these
discoveries back to 1665 when Robert Hooke observed a thin slice of dried cork under
a microscope that he built himself. He noticed that the cork was
composed of tiny, separate compartments, which he called cells. He was the first person to use this
term, which we all understand today. If we look back at the options
provided in our question, we can see that answer choice (C) describes Hooke’s
contribution correctly. Since we are being asked which
option was not a major event in the development of cell theory, we can rule out this
answer.
In 1675, Antonie van Leeuwenhoek
built his own simple microscope. He was the first person to see
living microorganisms, including freshwater protozoans and algae. Answer choice (A) correctly states
van Leeuwenhoek’s contributions, so this option can be ruled out.
Next, in 1838, Matthias Schleiden
suggested that plant tissues were also composed of cells. A year later, another scientist
called Theodor Schwann went even further to suggest that animals, and therefore all
living things, were composed of cells. Answer choice (E) correctly states
Schleiden’s contribution, so this isn’t the answer to our question. However, answer choice (B) states
that Schwann identified that bacteria and viruses were single-celled organisms,
which we know is not true. This could be the answer to our
question. Let’s bear this in mind while we go
over the contributions of the last scientist, Rudolf Virchow.
In 1855, a German scientist named
Virchow proposed that all new cells arise from cells that already exist. This was in contrast to what people
believed at the time, which was that cells could spontaneously come into
existence. Answer choice (D) correctly
identifies these contributions, so we can rule out this option also.
Therefore, the option that was not
a major event in the history of the development of cell theory is given by answer
choice (B), Schwann identifying that bacteria and viruses were single-called
organisms.
