1. Table of Contents
Photosynthesis
Respiration
Cell Division
Cancer

2. Sources of Energy - Photosynthesis
Nearly all living things obtain energy either directly or indirectly from the energy of sunlight captured during photosynthesis.

3. The Photosynthesis Process Activity
Click the Active Art button to open a browser window and access Active Art about the photosynthesis process.

4. The Two Stages of Photosynthesis
During photosynthesis, plants and some other organisms use energy from the sun to convert carbon dioxide and water into oxygen and sugars.

5. Steps in Photosynthesis
Sequencing
Sequence is the order in which the steps in a process occur. As you read, create a flowchart that shows the steps in photosynthesis. Put each step in a separate box in the flowchart in the order in which it occurs.
Steps in Photosynthesis
Sunlight strikes leaf.
Chlorophyll captures light energy.
Cells use the energy to produce sugars and oxygen from water and carbon dioxide.

6. Click the Video button to watch a movie about photosynthesis.

7. End of Section: Photosynthesis

8. Two Stages of Respiration
During respiration, cells break down simple food molecules such as sugar and release the energy they contain.

9. Photosynthesis and Respiration
You can think of photosynthesis and respiration as opposite processes.

10. Using Prior Knowledge - Respiration
Your prior knowledge is what you already know before you read about a topic. Before you read, write a definition of respiration in a graphic organizer like the one below. As you read, revise your definition based on what you learn.
What You Know
Respiration is when an organism breathes in oxygen because oxygen is needed by cells.
What You Learned
Respiration also means the process in which cells break down simple food molecules such as sugar and release the energy they contain.

11. Click the Video button to watch a movie about respiration.

12. Links on Cellular Respiration
Click the SciLinks button for links on cellular respiration.

13. End of Section: Respiration

14. Mitosis - Cell Division
During mitosis, the cell’s nucleus divides into two new nuclei. One copy of the DNA is distributed into each of the two daughter cells.

15. - Cell Division
The Cell Cycle

16. Cell Cycle Activity - Cell Division
Click the Active Art button to open a browser window and access Active Art about the cell cycle.

17. Length of the Cell Cycle
- Cell Division
Length of the Cell Cycle
How long does it take for a cell to go through one cell cycle? It all depends on the cell. A human liver cell, for example, completes one cell cycle in about 22 hours, as shown in the graph. Study the graph and then answer the following questions.

18. Length of the Cell Cycle
- Cell Division
Length of the Cell Cycle
Reading Graphs:
What do the three curved arrows outside the circle represent?
The longest curved arrow represents the cell’s interphase; the shortest represents cytokinesis; and the middle one represents mitosis.

19. Length of the Cell Cycle
- Cell Division
Length of the Cell Cycle
Reading Graphs:
In what stage of the cell cycle is the wedge representing growth?
Interphase

20. Length of the Cell Cycle
- Cell Division
Length of the Cell Cycle
Interpreting Data:
In human liver cells, how long does it take DNA replication to occur?
10 hours

21. Length of the Cell Cycle
- Cell Division
Length of the Cell Cycle
Drawing Conclusions:
In human liver cells, what stage in the cell cycle takes the longest time?
Interphase

22. Structure of DNA - Cell Division
The DNA molecule is shaped like a twisted ladder.

23. Replication of DNA - Cell Division
Because of the way in which the nitrogen bases pair with one another, the order of the bases in each new DNA molecule exactly matches the order in the original DNA molecule.

24. Sequencing - Cell Division
As you read, make a cycle diagram that shows the events in the cell cycle, including the phases of mitosis. Write each even in a separate circle.
The Cell Cycle
Cell grows, makes a copy of DNA.
Cell pinches in two; each daughter cell has same number of identical chromosomes.
Chromosomes and spindle fibers form; nuclear envelope breaks down.
Chromosomes stretch out; new nuclear envelope forms around chromosomes.
Chromosomes line up across the center and attach to a spindle fiber.
Centromeres split; chromatids separate and move to opposite ends.

25. End of Section: Cell Division

26. - Cancer
What Is Cancer?
Cancer is a disease in which cells grow and divide uncontrollably, damaging the parts of the body around them.

27. Previewing Visuals - Cancer
When you preview, you look ahead at the material to be read. Preview Figure 17. Then write two questions you have about the illustrations in a graphic organizer like the one below. As you read, answer your questions.
How Cancer Spreads
Q. What is a tumor?
A. A mass of abnormal cells that develops when cancerous cells divide and grow uncontrollably.
Q. How does cancer spread?
A. Some of the tumor cells can break off and enter the bloodstream.

28. Click the SciLinks button for links on cancer.

29. End of Section: Cancer

30. Comparing Photosynthesis and Respiration
Graphic Organizer
Comparing Photosynthesis and Respiration
Feature
Photosynthesis
Respiration
Water and carbon dioxide
Raw materials
Oxygen and sugars
Water and carbon dioxide
Products
Oxygen and sugars
Is energy released? No
Yes

31. End of Section: Graphic Organizer