1. Date: January 14, 2016 Aim #46: Why do cells need to divide? HW: 1)Read Chapter 10-1 (Cell Growth) pages 241-243 2)Quarterly Exam Tuesday 1/26 (periods 1 & 7) and Wednesday 1/27 (period 5) 3)Plant Packet due Monday, February 1 st !!! (follow calendar of deadlines) Do Now: Warm-Up Notebook DateTitle of Activity Page # 1/14Surface Area to Volume Ratio 79

2. Aim #46: Why do cells need to divide?

3. Compare the size of these organisms Vs.

4. 1) Do these organisms have different size cells? No, the cells of a large organism are the same size of a small organism. 2) How do organisms get so big? Cell Division

5. 3) Why do cells divide rather than grow in size? XX +

6. DNA “Overload” DNA Library Small Town City The larger the cell, the greater the demands on the DNA library. Eventually, the cell’s DNA would no longer be able to serve the increasing needs of the growing cell.

7. 4) Exchange of Materials What part of the cell is responsible for the exchange of materials in and out of the cell? Cell Membrane The rate at which particles are able to move across the cell membrane depends on the surface area of the cell (the amount of the cell surface exposed to the environment). SA Rate of Exchange

8. 5) Surface Area Small particles have a relatively larger surface area than large particles. What will melt first? Ice Cube Ice Chips Vs. Why? The smaller chips have more surface area. Smaller cells have more surface area and can exchange materials across membrane more efficiently.

9. 6) What is Cell Division? The process by which a cell divides into 2 new daughter cells.

10. 7) What happens to chromosomes before a cell divides? The chromosomes are replicated before a cell divides. Replication is the process by which DNA makes a copy of itself

11. 9) Why is it beneficial for daughter cells to be smaller? Smaller size of daughter cells increases the surface area and increases rate of exchange of materials across the membrane.

12. Chromosomes What are chromosomes made up of? DNA and Protein The chromosomes are replicated before a cell divides. Chromosome Replication 2 Chromatids + Centromere Chromosome Chromatids Centromere

13. When do cells divide? Organism Growth Cells at the root tips divide very rapidly

14. When do cells divide? Repair

15. 12) What tissues in our body need to undergo a lot of cell division? Skin Stomach Bone Why? The cells of these tissues are constantly growing or repairing themselves.

16. Cell Cycle 1)G1 Phase- Cells increase in size and synthesize new proteins and organelles. 2)S Phase- DNA (chromosomes) are replicated. 3)G2 Phase- Many of the molecules and organelles for cell division are produced. 4) M Phase- the cell undergoes cell division. Does anybody know what the “M” stands for? Mitosis

17. Mitosis Images Chromosomes Spindle Fibers Mitosis is the process that divides the cell’s nucleus into two, each with a complete set of genetic material from the parent cell.