Science – 7 Name: KEY Video: Greatest Discoveries in Biology (Cell Division) Date: ______
Scientist Year Contribution Walther Flemming 1881 Published book on cell division. Described cell division in great detail using more powerful microscope and dying techniques. Found chromosomes in cells. Discovered that chromosomes split. Named the process mitosis.
Edouard Van 1883 Observed that sex cells Beneden had half the number of chromosomes of regular cells.
August Weismann 1887 Discussed HOW sex cells could end up with half the number of chromosomes. Named the process meiosis.
Hans Driesch 1890’s Used sea urchins to investigate how cells differentiate into specific cell types.
Questions:
1. What is cell division?
Cell division is the process a cell goes through to duplicate itself.
2. Why did Flemming look at the TAIL of a tadpole to observe cell division?
He looked at the tail because it was growing so that’s where cell division would take place
3. Why was the discovery of chromosomes splitting during mitosis important?
It explains how one cell can turn into a multicellular organism with many interacting cells.
4. What was the difference, in number, between body cells and sex cells in the roundworms observed by Von Beneden?
Nearly all of the cells contained 4 chromosomes, except for the sperm and egg cells, which contained only 2.
5. Weissman’s experiments showed that at some point, a developing organism signals its cells to divide the number of chromosomes in half. What is this process called?
The process is called meiosis.
6. What is “cell differentiation?” Cells receive their assignments for specific jobs in the adult organism. Examples are legs, arms or eye cells.
7. What are cells that can develop into ALL cell types called?
Stem cells.
8. Why is stem cell research so important? What is the potential of stem cells?
It shows that cells’ roles are not always predetermined and that certain stem cells might be able to be used to treat disease. In regenerative medicine it has been shown that stem cells can repair tissue in muscle, in the brain and in the liver.