Cell Division
Why do you think cells divide?
Let s Review Before Rudolph Virchow made his contributions to cells, there was still debate over how new cells came to be. He observed new cells being made under a microscope. He saw that all cells come from pre-existing cells. He discovered cell division.
Types of Cell Division Depending on the cell type, cell division occurs in different ways. Prokaryotic cells undergo Binary Fission Eukaryotic Cells undergo Mitosis Reproductive Cells undergo Meiosis We will not be learning about meiosis just yet.
What is Binary Fission? The division and production of prokaryotic cells. Binary Fission- The process results in the reproduction of a living prokaryotic cell by dividing into 2 parts that each have the potential to grow to the size of the original cell. https://www.youtube.com/watch? v=th4v_q1ihfy https://www.youtube.com/watch?v=yia-rhx0xgi
How Does Binary Fission Occur? Binary Fission starts and ends in a 6 step process: 1. The bacteria at the start of the process is tightly coiled. 2. The DNA is replicated. 3. The DNA is pulled to separate poles of the bacteria as the cell increases in sizes and prepare for splitting. 4. The growth of the new cell begins to separate the bacteria. 5. The new cell wall fully develops, resulting in the splitting of the bacteria. 6. The new cells are fully separated and the DNA coils tightly.
What is Mitosis? The division and production of most eukaryotic cells. Mitosis- chromosomes in a nucleus are separated into 2 identical sets of chromosomes, each in its own nucleus. Chromosomes- DNA that is wound up in eukaryotic cells. Once the two nuclei are formed, the cell will start to separate. https://www.youtube.com/watch?v=g wcwszifklm
Events During Mitosis Interphase- DNA is replicated and proteins are produced. Prophase- the nucleus fades and the replicated chromosomes (DNA) start to break away. Metaphase- DNA is aligned. Anaphase- The DNA is pulled apart more and begin moving to cell poles. Telophase- The two cells start pulling apart. Cytokinesis- The cell is completely split.
Cool Discoveries That Support Cell Division
Francesco Redi An Italian scientist that lived from 1626-1697. He made a discovery about cell division before cell division was created. He was one of the first scientists to refute a theory called Spontaneous Generation Where life of simple creatures fleas and flies can come spontaneously.
Redi s Experiment Redi placed meat in two jars, he put a lid on one and left the top of one jar exposed. He let the jars sit naturally for a few days and observed what happened in the jars. The jar that did not have a lid eventually had maggots and those maggots hatched into flies. The jar that had a lid did not get maggots.
Louis Pasteur French scientists that lived from 1822-1895. He made great discoveries in vaccinations, fermentation, and pasteurization (named after him). He also did experiments to refute the Spontaneous Generation theory. Up until Pasteur completed his work, there was still debate about whether or not microbial (cell) life can form spontaneously.
Pasteur s Experiment He placed broth in two flasks, and boiled them to kill any life. After the broths have been heated, Pasteur broke off the lid on one of the containers and left one lid intact. Over time, the broth in the exposed flask became cloudy, a sign that microbial life existed, but the container with the lid remained clear.
So What? Redi and Pasteur s experiments made significant impacts on our knowledge of life and cells. Before these scientists made these experiments, it was widely accepted that life was a spontaneous occurrence and can happen with no assistance. Because both of these men showed that when you deny dust and air from entering a source, life cannot form. This disproved the accepted science that life is a spontaneous phenomenon. Because life is not spontaneous, all life has to come from a pre-existing source (cell division).
A cool simulation http://www.phschool.com/atschool/phsciexp/active_art/redi_pasteur_e xperiment/