Why do animals shed their skin?

How do little elephants grow up to be BIG elephants?

CELL DIVISION

Sexual Reproduction Human Life begins with sexual reproduction Sexual Reproduction is a mixing of DNA from two different organisms.

Fertilization When sperm meets egg they merge into one cell with a new set of DNA (46 chromosomes).

Asexual Reproduction is making an EXACT copy of DNA. The process of asexual reproduction begins after a sperm fertilizes an egg.

Three reasons why cells reproduce by asexual reproduction: 1. Growth 2 Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly.

Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm Interphase Prophase Metaphase Anaphase Telophase & Cytokinesis

1 st: Interphase occurs before mitosis begins Chromosomes make EXACT copies of themselves. (# doubles) The process is called replication. CELL MEMBRANE Nucleus Cytoplasm

Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

2nd: Prophase Mitosis begins (cell begins to divide) Nucleus prepares for cell division. Original Chromosome and its copy link together like an X Centrioles Sister chromatids Spindle fibers

Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

3rd: Metaphase 2nd step in Mitosis The original chromosomes and the copies attach to the spindle fibers. They line up in the center of the cell. Centrioles Spindle fibers

Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

4th phase: Anaphase The chromosomes and the copies separate. ‘ They are pulled to opposite sides of the cell. A new nucleus begins to form around each set of chromosomes. Centrioles Spindle fibers

Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

5th: Telophase Two new nuclei form. Chromosomes appear as chromatin (threads rather than rods). Mitosis ends. Nuclei Nuclei Chromatin

Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Cytokinesis occurs after mitosis Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

Animal Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Plant Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Cell Cycle

- Cell Division The Cell Cycle 24

Mitosis Animation http://www.cellsalive.com/mitosis.htm