BIOLOGY – Cell Division Unit 2 Cell Division Why do cells need to divide? Cells divide to continue their life process just as multicellular organisms must reproduce – so do unicellular organisms. There are three major types of cellular reproduction: 1. binary fission – prokaryotic organisms (unicellular) 2. mitosis – eukaryotic organisms (multicellular) 3. meiosis – sex cells (gametes – sperm & egg cells – multicellular) In binary fission, cells make a genetically identical copy of themselves. It starts with an original cell and ends with two “daughter cells”. The daughter cells are identical clones of the “mother” cell. Cell Division Cell Division Mitosis is cell division that is more complex than binary fission and occurs in eukaryotic organisms. Mitosis involves centrioles and spindle fibers. Mitosis is only ONE phase of the cell cycle. We will discuss more about cell cycle later in the unit. What do centrioles and spindle fibers do? They pull apart a cell’s genetic material after it has been replicated. There are four different phases of mitosis. What are they? prophase metaphase anaphase telophase What is interphase?? This is the phase in which the cell is just living life! YouTubeVid YouTubeVid YouTubeVid Cell Division During prophase of mitosis, centrioles become active and genetic material condenses to form chromosomes. Also, the nuclear membrane disappears. Cell Division During metaphase of mitosis, spindle fibers attached to centrioles help the chromosomes to line up along the center of the cell that is dividing. Cell Division During anaphase of mitosis, the genetic material begins to pull apart so that each new daughter cell will have an exact copy of the mother cell’s genes. Cell Division During telophase of mitosis, an original mother cell begins to form two new daughter cells with identical genetic material (or genes). Also, a nuclear membrane begins to form around each newly developed daughter cell. Cell Division During cytokinesis, the cell actually splits into two separate but genetically identical cells. Cyto- prefix refers to the cytoplasm while –kinesis suffix refers to the energy of motion. Cell Division Cell Division ARE YOU READY FOR A POP QUIZ??? Cell Division 1. Prokaryotic cells generally reproduce by _________ __________. 2. Eukaryotic cells generally reproduce by __________. 3. The phase of the cell cycle in which a cell is replicating its organelles, duplicating its genetic material and proof reading the duplication is called _______________. 4. The phase of the cell cycle in which a cell’s nuclear membrane begins to disappear and centrioles become active is called __________. 5. The phase of the cell cycle in which condensed chromosomes line up along the middle of a single cell is called __________. 6. The process of a cell actually dividing into two identical daughter cells is called __________. 7. The phase of the cell cycle in which the genetic material is separated into two identical regions is called __________. 8. The phase of the cell cycle in which the genetic material is just beginning to be pulled apart is called _______________. 9. In your own words, describe why a cell must divide. 10. Which is your favorite phase of mitosis and why? Cell Division The eukaryotic cell cycle consists of four phases. What are they? G1 “growth one” S “synthesis” G2 “growth two” M “mitosis” During G1, cellular components – organelles – IE mitochondria, ribosomes, vacuoles, cytoskeleton, etc… are duplicated. Chromosomes are NOT duplicated. During S, genetic material – chromosomes – are duplicated. During G2, cells proof read the duplication of genetic material. During M, cells divide – prophase, metaphase, anaphase, telophase & cytokinesis. Cell Division Cell Division Sex cells (IE sperm & egg cells), or gametes, undergo a different type of cell division. One cell becomes FOUR cells rather than just two. Whats more, the four new cells have genetic variability – they are not clones! This type of cell division is called meiosis. Meiosis ensures genetic variability during sexual reproduction. Only multicellular organisms’ gametes undergo meiosis. Genetic variability is important for biodiversity. Biodiversity is an evolutionary tactic that helps improve the success of any one individual living species. Do either of your parents have the same eye color as you do? Are you taller or shorter than your mother? Your father? Genetic variability ensures that we possess a variety of biological characteristics that may be necessary under certain circumstances. Cell Division Cell Division Ok, but, what is biodiversity??? Cell Division Cell Division DO YOU KNOW WHAT TIME IT IS?? POP QUIZ TIME!! Cell Division 1. Bacteria undergo what type of cell division? 2. Animal cells undergo what type of cell division? 3. Plant cells undergo what type of cell division? 4. Gametes (sex cells) undergo what type of cell division? 5. Why is meiosis important? 6. In your own words, describe what is meant by the term “biodiversity”. 7. Why do you think biodiversity is important? 8. What is the difference between mitosis and meiosis? 9. Do prokaryotic cells undergo meiosis? 10. If one original (mother) gamete undergoes meiosis, how many daughter cells will be produced? Cell Division CONGRATS!!