WHERE LIFE HAPPENS
1. Living things can be either uni-cellular (one cell) or multi cellular. A bacteria is one type of unicellular. 2. About 8000 of the smallest bacteria could fit inside one of your red blood cells. 3. The longest cells are the thin nerve cells found in large animals and they can be more than a meter long. 4. The cell with the greatest volume is an unfertilized ostrich egg 5. A cell's shape is related to its function. For example, a long nerve cell is long and it carries messages from your spine to your toes. The contraction and relaxation of muscle tissue is responsible for the movement in animals.
A SMALL NEW WORLD
1. In the 1600's people only knew about organisms they could see with the unaided eye. 2. A trio of Dutch eyeglass makers invented the microscope in the late 1500's. It consisted of a tube with lenses ground from rock crystal, and it magnified objects up to 9 times their actual size. 3. In 1665 the British scientist Robert Hooke published a set of drawings illustrating what he had observed with a microscope. 4. In the early 1670's Anton van Leeuwenhook, a Dutch fabric-store owner, began to grind lenses as a hobby. He used handheld microscopes to examine materials such as pond water and blood.
BIOLOGISTS BUILD A THEORY
1. By the 1830's many biologists were using the microscope as their chief investigative tool 2. Mathias Schleiden was a botanist, a scientist that studies plants. He found that plant parts he examined were made out of cells. In 1838 Schleiden made the generalization that all plants are made of cells. 3. Theodor Schwann was studying and animals. His microscopic investigations of animal parts led him to generalize that all animals were made of cells. 4. In 1858, a German doctor named Rudolf Virchow disputed the idea of spontaneous generation. Virchow reasoned that new plant cells arise only from existing plant cells, and new plant animal cells arise only from existing animal cells....
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