Science / Cell Theory
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Autor: anton 28 August 2010
Words: 481 | Pages: 2
Historical Development â€“ Cell Theory
1. Robert Hooke â€“ 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 â€“ an organism so small it would not be seen again for another two centuries.
3. R.J.H. Dutrochet â€“ 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 â€“ 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 â€“ He discovered one â€“celled animals called rhizopoda, now called protozoa in 1834.
6. Matthias Schlieden â€“ In 1838, he suggested that the nucleus and cell development are closely related. He decided that each plant cell leads a double life â€“ one independent, involving its development, the other as an integral part of the plant.
7. Theodor Schwann â€“ 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 â€“ 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 â€“ 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 â€“ 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 â€“ 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.
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