This document discusses cell division through mitosis and asexual reproduction. It begins by outlining the essential questions and vocabulary. It then explains that mitosis is a process of cell division that results in two identical daughter cells, each with the same number and type of chromosomes as the original parent cell. The four main steps of mitosis are prophase, metaphase, anaphase and telophase. Asexual reproduction is any form of reproduction that does not involve fusion of gametes and results in offspring that are genetically identical to the parent organism.

1. Chapter 4
Section 1
Cell Division - Mitosis

2. Essential Questions
• Why is Mitosis important?
• What are the steps of mitosis?
• How is mitosis different in plants and animals?
• What is asexual reproduction?

3. Vocabulary
• Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
• Chromosome
• Asexual Reproduction

4. Vocabulary
• Fission
• Budding
• Regeneration
• Chromatids
• Centrioles

5. Cells Divide!
• One cell becomes two cells.
• Two cells become four cells.
• Four cells become eight cells.
• And so on……

6. Why is cell division important?
• Blood cells wear out and are replaced.
• Skin cells wear out and are replaced.
• All organisms need to have cells which can
divide.

7. The Cell Cycle
• Every living organism has a cell cycle.
• What stage of your life cycle are you in?

8. Length of Cycle
• The cell cycle is a series of events that takes
place from one cell division to the next.
• The amount of time it takes varies depending
on the type of cell.
• Some cells take 19 hours to complete one
division.
• Some cells take less than 20 minutes to
complete one division.

9. Interphase
• Most of the life of any eukaryotic cell (cell
with a nucleus) is spent in a period of growth
and development.
• Cells like nerve cells and muscle cells no
longer divide so they are always in interphase.

10. Interphase
• Actively dividing cells, like skin cells, prepare
for division by copying their hereditary
material.
• Why is it important for cells to make copies of
their hereditary material?
• Hereditary material is found in the
chromosomes in the nucleus.

11. Coiled Hereditary Material
• Hereditary material (DNA) is like a long spiral
ladder.
• Chromosomes have to coil up before they can
duplicate.

12. Chromosomes
• Duplicated chromosomes are called
chromatids, held together at the center called
the centromere.

13. Mitosis
• The nucleus divides to form two identical
nuclei.
• The cell divides to form two identical cells.
• It takes four steps:
– Prophase
– Metaphase
– Anaphase
– Telophase

14. Prophase – step 1
• The nuclear membrane disintegrates.
• Why is that important?
• Two small structures, called centrioles, begin
to move to opposite ends of the cell.
• Thread-like spindle fibers begin to stretch
across the cell.

15. Metaphase – step 2
• Pairs of chromatids line up across the center
of the cell.
• The spindle fibers come from each side and
attach to the centromere.

16. Anaphase – step 3
• Each centromere divides, and the chromatids
separate.
• The spindle fibers shorten, pulling the
chromatids towards opposite sides of the cell.
• The separated chromatids are now
chromosomes.

17. Telophase – step 4
• Spindle fibers start to disappear.
• Chromosomes start to uncoil and a new
nucleus forms around them.
• The cytoplasm splits and the divided cell
membrane closes around two identical cells.

18. Division of Cytoplasm
• In animal cells, the cytoplasm divides and the
cell membrane pinches off.
• In plant cells, new cell walls form along a cell
plate which develops as the cytoplasm
divides. (see figure 4 on page 98 of your book)

20. Results of Mitosis
• Two identical nuclei are formed
• Each nucleus has the same number of
chromosomes.
• Every cell in an organisms body has the same
number of chromosomes.
• Humans have 46 chromosomes in each cell.
• Fruit Flies have only 8.

21. Asexual Reproduction
• Asexual reproduction cannot happen without
cell division.
• A new organism (sometimes more than one) is
produced from one organism.
• The new organism is genetically identical to
the parent.

22. Cellular Asexual Reproduction
• This is done by cell division.
– Examples are strawberries and potatoes.

23. Asexual Reproduction - Fission
• Bacteria do not have a nucleus so they cannot
divide by mitosis.
• Bacteria use a process called fission.
• Bacteria copy their genetic material and then
divide into two identical organisms.

24. Asexual Reproduction - Budding
• Budding is a process where a new organism is
grown from the body of the parent.
• The new organism is identical to the parent.
• An example is the Hydra. (see figure 8 on
page 102 in your book)

25. Asexual Reproduction - Regeneration
• You can’t grow a new finger but some
organisms can grow new body parts.
• Growing a new body part is called
regeneration.
• Some organisms, like sea stars, can shed an
arm.
– Each arm can grow into a new sea star.

26. Review
• Why is Mitosis important?
• What are the steps of mitosis?
• How is mitosis different in plants and animals?
• What is asexual reproduction?