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Answers Chapter 5 Questions.notebook
June 02, 2015
Questions ­ Chapter 5
1. Explain why the skin cells of an adult must divide. (136)
Because skin cells need to be replaced as they get worn out.
2. Why is cell division necessary in multicellular organisms? (138)
For growth and repair and to replace worn out cells.
3. List the three stages of the cell cycle. (139)
Interphase, mitosis and cytokinesis
4. Why is DNA replication so important? (140)
Replicating DNA ensures the newly formed cells will have an identical copy of the genetic information contained in the DNA molecule.
5. Outline the activities in the cell at each of the following phases of interphase: (a) growth and preparation(139)
Cell increases in size and makes proteins necessary for it to function. Some organelles begin to duplicate.
(b) replication (140)
DNA copies itself.
(c) continued growth and preparation (141)
Cell makes materials such as proteins and duplicates organelles such as mitochondria and chloroplasts.
Answers Chapter 5 Questions.notebook
June 02, 2015
6. What is the function of mitosis? (142)
To divide the contents of the cell's nucleus so that the daughter cell will have the same number and kinds of chromosomes as the original cell.
7. Why must the nuclear membrane disintegrate during prophase? (142)
So the chromosomes are free to move to opposite ends of the cell later.
8. Explain what might happen if the chromosomes did not separate correctly during anaphase. (143)
The cell would probably not go through the rest of the cell cycle. The cell will die, or one daughter cell would end up with more chromosomes than the other.
9. What are the phases of mitosis? (142­143)
Prophase, metaphase, anaphase and telophase
Answers Chapter 5 Questions.notebook
June 02, 2015
10. Use the diagrams on the right to answer questions (a) to (e). (142­143)
(a) Which diagram shows a cell at the beginning of anaphase? A
(b) Which diagram shows a cell with single stranded chromosomes moving to opposite poles? A
(c) Which diagram illustrates a cell where a new nuclear membrane is forming? D
(d) Write down the correct sequence of letters to show the phases of mitosis from beginning to end. C B A D
(e) Using the diagrams, explain how you could tell whether a cell has just completed mitosis or is entering mitosis.
If chromosomes are double stranded it is entering mitosis. If chromosomes are single stranded it is leaving mitosis.
Answers Chapter 5 Questions.notebook
June 02, 2015
11. Look at the following cells. (142­144)
(a) What type of cells are they? Plant cells
(b) Explain how you know. They appear to have a cell wall and stay next to each other after division.
(c) Write down the correct sequence of letters to show the phases of mitosis. C A D B
(d) Write down the name and a brief description of each phase.
Answers Chapter 5 Questions.notebook
June 02, 2015
12. How many daughter cells are formed during mitosis? (143­144)
13. How can binary fission lead to your becoming sick shortly after a few bacteria enter your body? (143)
Bacteria multiply very quickly by binary fission. A small number of bacteria entering your body can multiply into millions in only a few days. Bacteria can take as little as 20 minutes to reproduce.
14. Make a sketch to illustrate how mitosis in plant cells differs from mitosis in animal cells. (144)
Answers Chapter 5 Questions.notebook
June 02, 2015
15. How does cytokinesis differ in plant and animal cells? (144)
In animal cells the cell pinches together and the cytoplasm divides. In plants a cell plate forms across the middle and a new cell wall forms.
16. What is the importance of checkpoints in the cell cycle? (145)
The cell can be stopped from growing or dividing if the conditions are unsuitable.
17. What may happen when checkpoint proteins no longer function? (145)
This could occur when a mutation occurs and it could lead to a loss cell cycle control, which could lead to cancer.
18. What are two characteristics of asexual reproduction? (152)
1) Only one parent required. and 2) all the offspring are genetic clones of the parent.
19. Why is cell division necessary in unicellular organisms? (154)
To allow organisms to reproduce in great numbers.
20. Match the following types of asexual reproduction with the examples in parts (a) to (e). (154­160)
A. binary fission b
B. budding
C. fragmentation
D. vegetative reproduction
E. spore
(a) a cutting taken from a houseplant
(b) bacteria
(c) hydra
(d) an animal that grows from a piece that has separated from the parent
(e) a reproductive cell that may be able to survive extreme conditions
Answers Chapter 5 Questions.notebook
June 02, 2015
21. How does budding in yeast differ from binary fission in amoebas? (154, 156)
When a yeast cell reproduces through budding a part of the cell pushes outward to form a bud. This bud then pinches off to form an exact replica of the parent..When an amoeba reproduces through binary fission the nucleus reproduces itself to allow for the formation of two entirely new daughter cells which are identical to each other and the original.
22. Explain why bacteria do not undergo mitosis. (155)
Bacteria do not have a nucleus.
23. Give an example of a unicellular organism that reproduces by budding. (156)
24. Sea stars are able to attach to oysters, pry open their shells, and eat the insides. Oyster farmers once tried to destroy sea stars by cutting them into pieces and throwing them back into the ocean. Predict what happened. (157)
Sea stars reproduced asexually by fragmentation and this just increased their population.
25. List three ways plants can reproduce asexually. (158)
Fragmentation; vegetative reproduction (such as runners or potato eyes); grafting, cuttings; spores.
26. Give three examples of commercial uses of vegetative reproduction. (158­160)
1) Plants can spread through a field without farmers needing to plant more
seeds. 2) Farmers can grow exact copies of plants that have desirable traits. 3) Plant growers can quickly reproduce houseplants by taking cuttings.
27. How do some spores survive unfavourable conditions? (160)
Some spores have tough outer coatings.
Answers Chapter 5 Questions.notebook
June 02, 2015
28. What unique advantage does spore production have over other asexual methods of reproduction? (160)
Because spores are very light the can be carried away from the parent by wind or water, so they don't compete for space and food with the parent.
29. What advantages do organisms that produce spores have over organisms that reproduce by budding or binary fission? (160)
Because spores are very light the can be carried away from the parent by wind or water, so they don't compete for space and food with the parent. Spores are also covered in a hard outer shell which makes them very durable. They can survive harsh conditions.
30. What are the advantages and disadvantages of asexual reproduction? (161)
Advantages: 1) large number of offspring in a short period of time, 2) large numbers can out compete other organisms for food and water, 3) very little energy required and 4) large numbers mean they can survive when conditions change. Disadvantages: 1) offspring are genetic clones of parents, 2) some will have to compete with parent for food and water and 3)changes to the environment can wipe out very large numbers
31. What would happen if a cell was unable to make protein to form fibres during mitosis?
Mitosis could not occur successfully since chromosomes would not be able to attach. So, chromosomes would be equally distributed between cells.
32. What is the major disadvantage of asexual reproduction? (161)
Very little variation so all the offspring are identical. If conditions change, all of the offsping could die