A new topic (still cellular)… Let’s learn Cell Division!!!

Cell Division Biology is the only science where division really means multiplication!

One “parent” cell becomes two… The resulting “daughter” cells are genetically identical to each other and to the original (parent cell). XYZ XYZ ---< (see? Each offspring xyz still has the info XYZ!)

The daughter cells are identical because the DNA is the same. DNA, with proteins (called histones), make up the chomosomes.

DNA codes for proteins that make an organism what it is. There will be much more about DNA later in the year.

So, before cell division, the DNA must be copied… Then there is one set of chromosomes for each of the two resulting cells. xyz in one daughter cell xyz ---> xyz xyz -----< xyz in the other daughter cell in the parent cell

So, cell division…WHY? The cell is too big Repair, replacement, rejuvenation Growth of a multicellular organism Reproduction, in single celled and very simple organisms The cell has enough nutrients and the correct signal to divide

Cell Size Cell function is not possible if the cell gets too big!

Growth (in multicellular organisms) All eukaryotic organisms start as one cell, a zygote. Then the zygote undergoes cell division many many many times to grow.

Repair Whether it is normal maintenance, or due to an injury, new cells repair the tissue.

Replacement When cells get old and less functional, they are replaced. Eventually, all cells can no longer reproduce. Then they just die or undergo apoptosis (programmed cell death.

Asexual Reproduction Single celled and very simple organisms make an entirely new organism. ASEXUAL REPRODUCTION (one parent organism, identical offspring) (sexual reproduction is different and we’ll look at that later)

Asexual Reproduction Also called vegetative reproduction BUDDING REGENERATION FRAGMENTATION

In Prokaryotes (bacteria, remember?) Binary Fission - split in two, divide in half…. This is another type of asexual reproduction (only involves one parent organism, gives identical offspring).

In Eukaryotes (with chromosomes in a nucleus) A second nucleus is produced in mitosis Then the cell’s cytoplasm splits during cytokinesis The cells have a cell cycle which we will learn more about.

Reporter Chart What? Why? Who? When? Where? How? Making two identical cells from one original cell…ASEXUAL REPRODUCTION Cell size, growth, repair, replacement,reproduction All cells…prokaryote do binary fission and eukaryotes do mitosis followed by cytokinesis When the time is right…size, nutrients, situation, regulation Inside the cell. Using cell energy, manipulation of parts of the cell..mitosis and cytokinesis OR binary fission What? Why? Who? When? Where? How?

Review for Understanding How many cells are produced during cell division? How are these daughter cells different from the parent cell? Is this sexual reproduction? Why can’t a cell get super big? How does a bacterium reproduce? How does a eukaryotic cell reproduce? What are some (3-4) reasons for cell division?