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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
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?
What is interphase??
This is the phase in which the cell is just living life!
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
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
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”
 “synthesis”
G2  “growth two”
 “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 &
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
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