Help me study for my Biology class. I’m stuck and don’t understand.
Scientists have determined that there are approximately 37.2 trillions cells in the adult human body! Of these 37.2 trillion cells, there are 200 different types containing about 20 different organelles or structures. The Cell Theory states “All cells come from pre-existing cells”, In other words, at all times some of these 37.2 trillions cells are dividing, have divided or are preparing to divide. That’s a lot of activity!
Cell division is just one of several stages that a cell goes through during its lifetime. The cell cycle is a repeating series of events that include growth, DNA synthesis, and cell division. The cell cycle in prokaryotes is quite simple: the cell grows, its DNA replicates, and the cell divides. In eukaryotes, the cell cycle is more complicated. There is two basic types of cell reproduction: Mitosis and Meiosis. Mitosis is the division of somatic cells. Where 1 parent cell produces 2 identical daughter cells. The major purpose for this process is to replace dead or worn out cells and promote growth. Binary fission is a process like mitosis but it’s purpose is asexual reproduction. Meiosis is the other type of cell division. Meiosis, ensures that humans have the same number of chromosomes in each generation. It is a two-step process that reduces the chromosome number by half—from 46 to 23—to form sperm and egg cells. When the sperm and egg cells unite at conception, each contributes 23 chromosomes so the resulting embryo will have the usual 46. Meiosis also allows genetic variation through a process of DNA shuffling while the cells are dividing.