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Cell Theory Contribution
Transcript of Cell Theory Contribution
Redi created a basis for refuting the idea of spontaneous generation and thus helping future scientists to advance to the idea that all cells originate from preexisting cells. The Technology/ Experiment:
Redi filled six jars with decaying meat. Three of the jars were sealed and three of them were not. The three jars that were unsealed attracted flies which laid eggs in the decaying meat, the eggs hatched into maggots. The three jars that were sealed did not have maggots. This disproved the idea that the maggots are spontaneously generated out of the decaying meat itself. Those faithful to the theory of spontaneous generation claimed that the lack of maggots in the sealed jar is due to the lack of fresh air not the egg laying flies. In order to refute this as well Redi repeated the experiment except instead of sealing the three jars he covered them with fine net with the same results as the original experiment. Zacharias and Hans Janssen were Dutch spectacle makers who began experimenting and inadvertently created the first microscope. The Technology/ Experiment:
Zacharias and Hans Janssen began experimenting by putting several lenses together in a tube when they discovered how much larger objects near the end of the tube appeared in comparison to a standard magnifying glass. The Janssen’ microscope was created with three draw tubes with lenses that were inserted into the tubes behind. One could focus the microscope by sliding the draw tube in or out. This microscope was capable of magnifying things up to 10x at its maximum. The Contribution:
The contribution of this microscope was integral to the evolution of lens magnification. This microscope was the first created besides the single-lens magnifying glass and was also a foundation for the advances of Anton van Leeuwenhoek and Robert Hooke. Robert Hooke, an English architect, natural philosopher and scientist, observed specimens with a microscope and recorded them in a published work called Micrographia. He is most famous for his observation of the slices of cork where he described the pores/”cells”. The Experiment/Technology:
Robert Hooke made his observations using a microscope. With this microscope he was able to observe specimens as small as a plant cell. Using his microscope Hooke was able to observe for the first time the cells of a plant. He saw their cell walls specifically as there was not enough detail or magnification capable for his microscope to identify any other organelles. The cells were called cells as they reminded him of cells in a monastery. The Contribution:
Hooke was the first to document a physical cell and is therefore integral to the development of cell theory as he was the discoverer of the cell with physical proof of its existence and also a basic organelle. His contributions also involved those in creating detailed pictures and studies on various insects as well as advances in telescopic observation of the planets. Anton van Leeuwenhoek was a Dutch tradesman and scientist who worked on developing and improving the microscope as well as contributed to microbiology. He began his work on microbiology observation and microscopes after seeing Hooke’s Micrographia. The Technology/ Experiment:
Leeuwenhoek’s designs mainly consisted of simple yet powerful magnifying glasses that he created himself by placing the small of a rod of soda lime glass into fire and when taken out was able to make this into two long pieces of glass. By inserting one piece back into the fire Leeuwenhoek was able to create a very small yet very powerful magnifying glass spheres which became his lenses. The microscope was simple in design only having the glass sphere as a lens contained in a brass plate, the adjustment of which could be done by turning two screws. The entire microscope was 3-4 inches long and required a light source. This simple microscope was capable of magnification of 200x while compounds of the age were only capable of 20x or 30x. The Contribution:
Not only did Leeuwenhoek introduce a new form of microscope capable of greater magnification and therefore helping to aid the discovery of more advances of the cell theory but he also discovered the existence of single-celled organisms. This helped support the cell theory in that all living things are composed of cells and added that they could in fact be composed of only one cell. John Needham, a Scottish scientist created an experiment that supported the theory of spontaneous generation or abiogenesis. The Technology/ Experiment:
Needham boiled a meat broth in order to kill the microbes and sealed the container, this was his experimental group. He created a control of boiled meat broth which was left in open air. Microbes were observed in both jars which Needham claimed was due to the fact that all non-living matter had life force in it. The Contribution:
Needham’s experiment fueled the work of Lazzaro Spallanzani and furthered the research in spontaneous generation. Lazzaro Spallanzani, an Italian scientist who helped to disprove the idea of spontaneous generation began his research after recognizing several deficiencies in Needham’s work. The Technology/ Experiment:
Spallanzani repeated the experiment of Needham except he boiled the meat broth for an hour because he discovered that boiling for five or ten minutes as Needham could have done would not have killed all microbes. He also sealed the containers by heating the top and therefore melting the glass to prevent microbes from being collected by the air. The Contribution:
The results of the experiment were that as long as the container remained sealed the broth would remain clear although once the seal was broken the water would become cloudy within hours. This helps to refute spontaneous generation by showing that microbes could not grow in a container while it was sealed. His discovery of the time in which it actually took to kill the microbes helped to improve the accuracy of these experiments. Robert Brown, a Scottish botanist and plant geographer, discovers the nucleus in cells and his description of continuous motion The Technology/ Experiment:
Robert Brown is known for being the first to identify the nucleus in a cell which he discovered while studying the fertilization of Orchidaceae and Asclepiadaceae. He observed through a microscope the structure in both the orchids and other plants he studied. This discovery was Brown’s contribution to the cell theory although he is responsible for the distinction between angiosperms and gymnosperms and the description of natural continuous motion. This discovery was observed by microscope as well when he noticed that both living and dead pollen grains exhibited the same kind of motion which he then used to form the basis for his theory that the motion was just a property of matter in that particular state. The Contibution:
Brown’s contribution of identifying the nucleus of a cell is significant to the cell theory because it helped people to better understand how cells function. The nucleus is a major organelle in the cell that helps aid in mitosis/ meiosis in eukaryotic cells and therefore is support of the idea that all cells come from pre-existing cells because the discovery of the nucleus and later its function would provide a better understanding of how cells reproduce. Brown also improved the classification of plants by creating and defining new genera and families. Matthias Jakob Schleiden, a German botanist, made the first generalization about the nature of cells, concluding that all plant tissues are composed of cells and that an embryonic plant grew from a single cell. He believed that the cell was the basic building block of all living matter. The Technology/ Experiment:
Schleiden observed plants microscopically while many other botanists of the time where only describing and classifying plants species. He determined that the recognizable units or cells were the building blocks of the plant itself. He determined that plants grew through producing new cells and determined that cells made up the entire plant and its functions. The Contribution:
The generalization that Schleiden made was the first generalization on the nature of cells and was similar to the current generalization in the cell theory that states that cells are the most basic form of life. The publication of his theory also instigated the investigation of Schwann who extended the cell theory to animals and brought the first generalizations of the cell theory together. Theodor Schwann, a German biologist, made the generalization that cells were not only the building blocks of plant life but also that of animals too. He created a theory that stated:
1.Cells are organisms and all organisms consist of one or more cells.
2.The cell is the basic unit of structure for all organisms which are arranged in accordance with definite rules. The Technology/ Experiment:
Theodor Schwann applied the cell theory of Matthias Jacob Schlieiden to the animal life he studied. He was able to demonstrate that the tissues of all animals can be traced to embryonic cells. Schwann also discovered the digestive enzyme, pepsin, in the stomach membrane tissues of animals. He conducted research on fermentation, purification and muscular and arterial contraction. His major achievement in biology was the second generalization of cells and important in the development of biology, that cells are the basic unit of life. The Contribution:
Theodor Schwann’s cell theory is important to the development of the modern cell theory by representing that the cell is the most basic unit of life and establishing the second generalization of the cell which entwined zoology and botany together. Previous to Schwann’s theory scientists debated whether there was a difference between the composition of animal and plant tissues. Schwann’s theory of cells being the most basic units of life became one of the most important in biology today. Rudolf Virchow, a German physiologist, physician, pathologist and anthropologist added the third and final addition to the cell theory; cells develop only from pre-existing cells (Omnis cellula e cellula). The Technology/ Experiment:
Rudolf Virchow determined through his pathological research that the symptoms and effects of diseases do not come from the tissues and organs of an organism, but that diseases come from pre-existing individual cells. The original concept of pathology was that diseases resulted from an imbalance of the four fluids in your body (blood, phlegm, yellow bile, black bile), then later it was accepted that diseases resulted from lesions around or on organs. When the cell theory was published and it became known that all cells come from pre-existing cells, he applied the theory to pathology and thus determine that diseases came from a microbiological source and not from any physical tissue or organ damage. The Contribution:
Virchow’s theory changed biology and people’s focus on preventing diseases. Without his advances there would not be any advances in research pertaining to diseases that stem from individual cell mutations such as cancer and also the idea that bacteria and viruses cause infection in organisms instead of the physical organs in the organism. Koch begins his work on diseases. By this time microscopists had proven the existence of bacteria and Louis Pastuer had shown that spontaneous generation is not a valid theory and that bacteria were responsible for spoiling food. It was on this principle that Koch believed bacteria could also cause diseases. The Technology/ Experiment:
Koch proved his hypothesis by identifying the organism that caused anthrax which is a disease that effects cattle and grazing animals later resulting in blood poisoning. For his experiment Koch established four criteria that had to be met.
1.The microbe must be in the patients suffering with disease and not in healthy individuals.
2.The organism must be grown in a pure culture and isolated.
3.If one injects this purely grown culture into an animal, the animla should exhibit symptoms
4.The organism should be isolated from the diseased experimental animal and proven to be the same organism after being grown in another pure culture. The Contribution:
These new criteria created by Koch are called Koch’s postulates which are now the basis for the germ theory of disease and established for medical fields that bacteria and viruses caused disease. This gave way to new advances in disease and antibiotics as well as lead to better sanitation practices because the problem had been identified. This also helped the cell theory advance and become applicable to all fields including medicine and not just nutrition and agriculture. This created a dramatic decrease in infant mortality rates due to a decreasing volume of disease spread. Louis Pasteur submits an experiment to refute the general notion that Spallanzini’s experiment was faulty because he eliminated the fresh air and that heating broth has skewed his results to the French Academy of Sciences. The Technology/ Experiment:
Pasteur sought to recreate the experiment conducted by both Needham and Spallanzani except he did so in such a way that his results could not be refuted as interfering with the process of spontaneous generation. Before heating the broth he heated the neck of the flask the broth would be boiled in and bent the neck into an “S” shape. Air could get to the broth although microbes would get caught in the neck of the flask. Pasteur used the same broth in both flasks as well as light and temperature conditions. The results of the experiment showed that the broth did not grow any microbes from itself and thus disproved spontaneous generation. Pasteur would have had the use of a microscope at his disposal although most likely did not need one to examine the mold in the neck of the clear flask. The Contribution:
Pasteur’s experiment was an achievement in microbiology and helped to advance the cell theory by allowing the theory of spontaneous generation to be put to rest as everyone could see that the microbes could only be produced from other microbes which proved the idea present in today’s cell theory in which all cells come from pre-existing cells. He also discovered that there are microbes in the air which helped to make many other experiments performed after him much more accurate. To be Continued...