WHAT IS A CELL? It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The cell is the basic structural and functional unit of all known living organisms. Some organisms are unicellular (made of only one cell) while others are multicellular (made up of several cells). The word cell comes from the Latin cellula, meaning, a small room. The term was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in. BRIEF HISTORY OF THE CELL THEORY The cell was first discovered by Robert Hooke in 1665. He examined very thin slices of cork and saw a multitude of tiny pores that he remarked looked like the walled compartments of a honeycomb. Because of this, Hooke called them cells, the name they still bear. The first man to witness a live cell under a microscope was Antonie Phillips van Leeuwenhoek, who in 1674 described the algae Spirogyra and named the moving organisms animalcules, meaning "little animals". Leeuwenhoek probably also saw bacteria. In 1839, Theodor Schwann and Matthias Jakob Schleiden suggested that cells were the basic unit of life. In 1858, Rudolf Ludwig Virchow concluded that all cells come from pre-existing cells, thus completing the classical cell theory. Classical Interpretation of the Cell Theory 1. All organisms are made up of one or more cells. 2. Cells are the fundamental functional and structural unit of life. 3. The cell is the unit of structure, physiology, and organization in living things. 4. The cell retains a dual existence as a distinct entity and a building block in the construction of organisms. 5. All cells come from pre-existing cells. Hand-out 1 in General Biology Unit 2: Cellular Structures and Function
The cell theory holds true for all living things, no matter how big or small, or how simple or complex. Since according to research, cells are common to all living things, they can provide information about all life. And because all cells come from other cells, scientists can study cells to learn about growth, reproduction, and all other functions that living things perform. By learning about cells and how they function, you can learn about all types of living things. Over time, and with the development of the electron microscope, the theory has continued to evolve. As more and more living material has been observed at higher and higher magnifications, much more has been learned, leading to the modern cell theory. The modern cell theory includes the basic components of the classic cell theory and then adds more… Modern Interpretation of the Cell Theory 1. 2. 3. 4. All known living things are made up of cells. The cell is structural & functional unit of all living things. All cells come from pre-existing cells by division. Cells contain hereditary information which is passed from cell to cell during cell division. 5. All cells are basically the same in chemical composition. 6. All energy flow of life occurs within cells. MICROSOPE A microscope (from the Greek “mikrós” meaning "small" and “skopeîn” meaning “to look”) is an instrument to see objects too tiny for the naked eye. Microscopes can be separated into optical theory microscopes, electron microscopes, and scanning probe microscopes. The most common type of microscope—and the first invented—is the optical microscope. This is an optical instrument containing one or more lenses producing an enlarged image of an object placed in the focal plane of the lenses.
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Compound Light Microscope The compound microscope uses lenses and light to enlarge the image. It is also called an optical or light microscope. The compound microscope has two systems of lenses for greater magnification: 1. the ocular, or eyepiece lens that one looks into, and 2. the objective lens, or the lens closest to the object.
Computing for Magnification Low Power Objective (4x) 10 Ocular...
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