Directed Reading B. Section: The Cell Cycle

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1 Skills Worksheet Directed Reading B Section: The Cell Cycle 1. When your body makes new cells, what is being replaced? a. water c. cells that have died b. energy d. heat 2. What does making new cells allow you to do? a. grow c. eat b. sleep d. make food THE LIFE OF A CELL 3. When does the cell cycle begin? a. when the cell is formed b. when the cell uses energy c. when the cell divides d. when the cell uses oxygen 4. When does the cell cycle end? a. when the cell is formed b. when the cell uses energy c. when the cell divides d. when the cell uses oxygen 5. What is the hereditary material inside a cell called? a. nuclei c. DNA b. water d. ATP 6. In what structures can cells DNA be found? a. bacteria c. fluids b. water d. chromosomes Holt Science and Technology 20 The Cell in Action

2 Making More Prokaryotic Cells Read the words in the box. Read the sentences. Fill in each blank with the word or phrase that best completes the sentence. more complex binary fission less complex DNA 7. Prokaryotic cells, without nuclei, are than eukaryotic cells. 8. Eukaryotic cells, with nuclei, are than prokaryotic cells. 9. Prokaryotic cells such as bacteria divide by. 10. When binary fission is complete, each new cell has identical. Eukaryotic Cells and Their DNA 11. How many chromosomes do humans have? a. 8 b. 48 c. 32 d What are pairs of similar chromosomes called? a. prokaryotic pairs b. homologous chromosomes c. DNA d. eukaryotic pairs Holt Science and Technology 21 The Cell in Action

3 Making More Eukaryotic Cells 13. How many stages does a eukaryotic cell cycle have? a. two b. three c. four d. five 14. When chromosomes are copied, what are the two copies called? a. DNA b. centromeres c. chromatids d. mitosis 15. When the chromosomes separate, what is the process called? a. mitosis b. copying c. parting d. duplicating 16. What does a cell do in the third stage of the cell cycle? a. dies b. divides into two identical cells c. makes food d. takes in oxygen Holt Science and Technology 22 The Cell in Action

4 MITOSIS AND THE CELL CYCLE Use the figure below to answer questions 17 through 20. Circle the letter of the best answer for each question. Mitosis Phase 1 Mitosis Phase 2 Mitosis Phase 3 Mitosis Phase Look at the figure. When does mitosis begin and the chromosomes condense into rodlike structures? 18. Look at the figure. When do the chromatids separate and move to opposite sides of the cell? 19. Look at the figure. When does a nuclear membrane form around each set of chromosomes, completing mitosis? 20. Look at the figure. When do the chromosomes line up, and the homologous chromosomes pair up? Holt Science and Technology 23 The Cell in Action

5 Cytokinesis 21. What is it called when the cytoplasm of a cell divides? a. mitosis b. interphase c. cytokinesis d. cell plates 22. What does the cell membrane do during cytokinesis in an animal cell? a. pinches in two b. forms a cell plate c. makes copies of its DNA d. shrivels up 23. What forms between the two new cells during plant cell cytokinesis? a. cell plate b. mitochondrion c. chromatid d. water Holt Science and Technology 24 The Cell in Action

6 TEACHER RESOURCE PAGE 6. prokaryotic 7. eukaryotic 8. prokaryotic 9. eukaryotic 10. prokaryotic 11. binary fission 12. the circle of DNA 13. DNA , 8, homologous chromosomes 16. Homologous chromosomes have the same sequence of genes and the same structure 17. organelles, chromosomes 18. chromatids 19. mitosis 20. Chromatids are held together at a region called the centromere. 21. The cell grows and copies its organelles and chromosomes. The chromosomes split into copies called chromatids.the chromatids twist into an X shape. 22. During the second stage of the cell cycle, the chromatids come apart. This separation is called mitosis. 23. During the third stage of the cell cycle, the cell divides into two cells that are identical to each other and to the original cell. 24. B 25. Phase Phase Interphase 28. Phase Phase Cytokinesis 31. In eukaryotic cells that do not have cell walls, the cell membrane pinches inward until it divides the cytoplasm and splits the cell in two Directed Reading B SECTION : EXCHANGE WITH THE ENVIRONMENT 1. energy and raw materials 2. cell membrane 3. healthy 4. wastes 5. D 14. C 6. C 15. B 7. A 16. B 8. C 17. A 9. C 18. B 10. D 19. B 11. A 20. B 12. B 21. A 13. D SECTION: CELL ENERGY 1. sun 2. food 3. reproduce 4. the sun 5. food 6. photosynthesis 7. energy 8. C 9. B 10. cellular respiration 11. fermentation 12. D 18. B 13. C 19. A 14. A 20. A 15. D 21. D 16. A 22. B 17. D SECTION: THE CELL CYCLE 1. C 2. A 3. A 4. C 5. C 6. D 7. less complex 8. more complex 9. binary fission 10. DNA 11. D 18. C 12. B 19. D 13. B 20. B 14. C 21. C 15. A 22. A 16. B 23. A 17. A Holt Science and Technology 90 The Cell in Action