Historical Development
Cell Theory
1. Robert Hooke In 1662, he
observed tiny compartments in the cork of a mature tree and gave them the Latin
name cellulae (meaning small rooms). This was the origin of the biological term
cell.
2. Anton Von Leeuwenhoek - By the late 1600s, he had observed diverse
protistans, sperm, even a bacterium an organism so small it would not be seen
again for another two centuries.
3. R.J.H. Dutrochet French botanist who
prepared plant cells and studied them between 1824 and 1830. He discovered and
named the phenomenon of osmosis, which is the passage of a liquid through a
semi-permeable membrane. He was the first to carefully study respiration and
light sensitivity in plants.
4. Robert Brown In 1827, he noticed the
constant presence of an opaque spot in egg cells, pollen cells, and then cells
of the growing tissues of orchid plants and called this spot protozoa in 1834.
5. Dujardin He discovered one celled animals called rhizopoda, now called
protozoa in 1834.
6. Matthias Schlieden In 1838, he suggested that the
nucleus and cell development are closely related. He decided that each plant
cell leads a double life one independent, involving its development, the other
as an integral part of the plant.
7. Theodor Schwann In 1839, after years
of studying the structure and growth of animal tissues, he concluded that
animals, as well as plants, consist of cells and cell products, and even though
the cells are part of a whole organism, they have an individual life of their
own.
8. Rudolf Virchow In 1849, he completed his studies of cell growth
and reproduction of their division into two cells. He concluded that every cell
comes from an already existing cell.
9. Walther Flemming In the early
1880s, while using dyes to study the structure of cells, he found a structure,
which strongly absorbed dye, and named it chromatin. He observed that the
chromatin separated into stringy objects during cell division, which became
known as chromosomes. Flemming named the division of somatic cells mitosis, from
a Greek word for thread. He also observed that the chromosomes formed two star
shaped structures on either side of the dividing cell, which he named asters.
10. C. Golgi In 1898, he described the existence of a network of thread
like structures and small sacs (vesicles) in the cytoplasm of nerve cells. This
complex organelle composed of flattened sacs and vesicles is now known as a
Golgi body or Golgi apparatus.
11. J.D. Watson and F.H.C. Crick In 1953,
after Watson realized that the shape of the base pairs meant they could only be
arranging in a certain way, Watson and Crick published a paper proposing that
the DNA moleule had double helical structure.
State the three principles
of the cell theory:
1. All organisms are composed of one or more cells.
2. The cell is a basic unit of life.
3. New cells arise only from cells
that already exist.