1. Thursday, November 3rd
Miss Brawley

2. Do Now: Name two reasons cells must divide.
List two differences between sexual and asexual reproduction.
Which type of reproduction yields genetically identical offspring?

3. Cell Growth Limitations
Information crisis: too many demands placed on DNA
Traffic problems: volume grows too fast relative to surface area, material exchange is insufficient
Ask: Considering the problem of surface-area-to volume ratio, how could cell growth create a problem that is similar to the traffic jam in the growing town?
Answer: As a cell grows, it needs more materials to cross its membrane. Traffic is comparable to the movement of materials such as nutrients, water, oxygen, and wastes across a cell’s membrane. As a cell grows larger (increasing volume), the number of traffic lanes (amount of surface area to cross) does not keep up, and materials cannot enter or leave the cell as quickly as necessary.
Click to reveal the problems caused by a decreasing surface-area-to-volume ratio for growing cells.
Reiterate that if a cell grew too large, it would not have enough relative surface area to get sufficient amounts of oxygen and nutrients into the cell and waste products out.

4. Chapter 10: Cell Growth and Division

5. Workbook

6. Cell division
Cell division is the process by which a cell divides into two new daughter cells
Solves the problem of increasing size by reducing cell volume, and increasing the Surface Area : Volume ratio for each daughter cell
EFFICIENT EXCHANGE OF MATERIALS IN CELL

7. Cell Division and Reproduction
Characteristics of living things!
Two types of Reproduction
Asexual and Sexual
Read pages and form a T-chart with a partner to compare the two types of reproduction

8. Asexual Reproduction
A single parent produces genetically identical offspring.
Remind students that reproduction is one of the most important characteristics of living things. Point out that for a single-celled organism like a bacterium, simple cell division makes the process of reproduction pretty straightforward, and it can allow a population to grow very quickly. This kind of cell division is a form of asexual reproduction, which is the production of genetically identical offspring from a single parent.
Click to reveal the bullet points.
Lead a discussion about how cell division relates to the process of asexual reproduction. To reinforce students’ knowledge, have them apply what they have learned to their everyday lives.
Ask: Why do bacterial infections spread so quickly through a school?
Answer: Bacteria can reproduce asexually, so they can reproduce quickly in the right environment, such as a crowded school.
Direct students to the photos of kalanchoe and hydra.
Ask: Both of these organisms are reproducing asexually. How are they different from the bacterium?
Answer: They are multicellular organisms.
Point out that tiny plantlets in the kalanchoe can break off and grow into full new plants. The bud on the hydra will eventually pinch off to become a separate individual.
Ask: What do the offspring off all three of these organisms have in common?
Answer: The offspring share the same genetic material as their parent.

9. Sexual Reproduction
Sexual reproduction involves the of two separate parent cells.
Offspring inherit some genetic information from each parent.
fusion
Remind students that at the start of the presentation you asked them about how asexual reproduction related to humans. Point out that humans, like other animals, grow and repair their bodies through cell division. But to reproduce themselves, humans use sexual reproduction.
Read the statement on the slide aloud.
Ask for a volunteer to identify verbally what term completes the statement.
Click to reveal the correct answer.
Tell students: Asexual reproduction involves separation of a cell. Sexual reproduction involves fusion, or joining, of cells.
Ask: How do offspring relate genetically to their parents?
Answer: They are not genetically identical to either parent. They inherit some genetic information from each parent.
Click to reveal the second bullet point.

10. Comparing Asexual and Sexual Reproduction
Produce many offspring in short period
Don’t need to find a mate
In stable environments, genetically identical offspring thrive.
If conditions change, offspring not well adapted.
Sexual
Relatively fewer offspring; growth takes more time
Need to find a mate
In changing environments, genetic diversity can be beneficial.
Offspring may be less well adapted to current conditions.
Lead a short discussion in which students consider how one form of reproduction might be more advantageous than another. Remind students that characteristics that make an organism well adapted to its environment are critical for survival.
Ask: Under what kind of conditions would it be helpful to be able to create a very large number of offspring in a short period of time?
Answer: when resources such as food and space are unlimited
Ask: Under what kind of conditions would it be useful to have offspring that are genetically identical to the parent?
Answer: when environmental conditions are stable
Ask: Under what conditions would it be helpful to need only one parent to reproduce?
Answer: when finding a suitable mate might be difficult or impossible
Ask: Under what kind of conditions would it be useful to have offspring that are not identical to either parent?
Answer: when environmental conditions are changing and new combinations of traits may promote survival
Then, ask students to identify, based on the discussion, what the advantages and disadvantages of asexual and sexual reproduction are.
After students have shared their thoughts, click to reveal the advantages and disadvantages.
Discuss each bullet point as it is revealed to ensure students understand why it is an advantage or disadvantage.
Be sure to point out that most organisms they are familiar with can use only one strategy to reproduce themselves. However, some organisms, such as yeast, can use both strategies. Typically yeast undergo cell division to reproduce asexually, but under certain conditions can enter a sexual phase. Point out that the ability to use both reproductive strategies can be an excellent adaptation for some organisms!

11. Before reproduction can happen…
Cells must first make a complete copy of their genetic information before cell division begins
What are the bundled/coiled packages of DNA called??
Prokaryotic vs Eukaryotic?

12. Eukaryotic Chromosomes
Chromosomes make it possible to separate DNA during cell division.

13. The Cell Cycle
The cell cycle is a repeated pattern of growth and division that occurs in eukaryotic cells.
This cycle consists of two phases:
The first phase represents cell growth
The last phase represents nucleic division (mitosis) and cytoplasmic division (cytokinesis).

14. Phase Assignments Interphase- Abigail, Daquan, Autumn
Mitosis: Prophase- Grayson, Kiana, Tina
Mitosis: Metaphase- Amber, Kelvon, Shania
Mitosis: Anaphase- Kayce, Tywuan, Saterrence
Mitosis: Telophase- Ariel, Damitria, Timothy
Cytokinesis- Ja’Tashjah, I’dae, Tori

16. Interphase
Cells spend the majority of the cell cycle in interphase. The purpose of interphase is for cell growth and preparation for mitosis and cytokinesis. By the end of interphase a cell has two full sets of DNA (chromosomes) and is large enough to begin the division process.
• Interphase is divided into three phases. Each phase is characterized by specific processes involving different structures.
• During the G1 (gap 1) phase, the cell grows and synthesizes proteins.
• During the S (synthesis) phase, chromosomes replicate and divide to form identical sister chromatids.
• During the G2 (gap 2) phase, cells continue to grow and produce the proteins necessary for cell division.

17. Mitotic Phase

18. Mitosis
The purpose of mitosis is the division of the nucleus; making two identical nuclei, each with the same number of chromosomes.
• The result of mitosis is two identical daughter cells. This is a form of asexual reproduction.
• Mitosis, which follows Interphase, is divided into four phases. Each phase is characterized by specific processes involving different structures.
• The characteristics of the phases of mitosis:

19. Prophase Chromosomes condense and are more visible.
The nuclear membrane (envelope) disappears.
By the end of prophase, the centrosomes (organelles that produce spindle fibers) have separated and have moved to opposite poles of the cell.
The formation of the spindle apparatus from the centrosomes.

20. Metaphase Chromosomes line up across the middle of the cell.
• Spindle fibers connect the centromere of each sister chromatid to the poles of the cell.
Chromosome composed of two sister chromatids
Image Source: SC Science Academic Standards Support Document 2005

21. Anaphase Sister chromatids separate.
Separated chromatids move to opposite poles of the cell.

22. Telophase Chromosomes (each consisting of a single chromatid) uncoil.
• A nuclear envelope forms around the chromosomes at each pole of the cell.
• Spindle fibers break down and dissolve.
• Cytokinesis begins.

23. Cytokinesis
Cytokinesis is the division of the cytoplasm into two individual cells. The process of cytokinesis differs somewhat in plant and animal cells.
• In animal cells the cell membrane forms a cleavage furrow that eventually pinches the cell into two nearly equal parts, each part containing its own nucleus and cytoplasmic organelles.
• In plant cells a structure known as a cell plate forms midway between the divided nuclei, which gradually develops into a separating membrane. The cell wall forms in the cell plate.

24. Animal Cell Telophase/Cytokinesis

25. Plant Cell Telophase/Cytokinesis