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2.7 Textbook Questions Select your pathway LEVEL 1: LEVEL 2: LEVEL 3: Questions 1, 2, 5, 9, 10, 15 Questions 3, 4, 7, 11, 14, 16 Questions 6, 8, 12, 13, 17, 18 Remember and understand 1. State whether the following statements are true or false. Rewrite any false statement to make it true. a. All cells come from pre-existing cells. b. Cells produced by mitosis are genetically identical to each other and to the parent cell. c. Mitosis involves division of the cytoplasm whereas cytokinesis involved division of the nucleus. d. Meiosis prevents the doubling of chromosomes at fertilisation because it produces cells with half the chromosome number of the original cell. e. Variation within a species can provide some individuals with an increased chance of surviving over others. f. Little to no variation among individuals within a species improves the chances of the species surviving. g. One way in which meiosis increases variation in sexually reproducing organisms is in terms of the number of combinations in which chromosomes can be divided up into the gametes. h. Crossing over of genetic information between each pair of chromosomes in meiosis is a source of variation in a species. 2. Match the term with its description in the following table. Term Definition a. Diploid A. Cells with four sets of chromosomes b. Fertilisation B. Cells with one set of chromosomes (e.g. as in human gametes) c. Gamete C. Cells with two sets of chromosomes (e.g. as in human somatic cells) d. Haploid D. Reduces the number of chromosomes in the daughter cells by half that of the parent cell e. Meiosis E. Sex cell f. Mitosis F. The fusion of gametes g. Tetraploid G. The result of two gametes fusing together h. Zygote H. Type of cell division important for growth, repair and replacement 3. List two differences between sexual and asexual reproduction. 4. State the names of the two main types of cell division. Explain why each is used. 5. a. List three functions of mitosis. b. Describe the features of the cells produced by mitosis. 6. Copy and complete the following table. TABLE Comparison of meiosis and mitosis Type of cell division Why use it? Where does it occur? Features of cells produced Mitosis Meiosis 7. With the use of a diagram, explain how the sex of a human baby is determined. Apply and analyse 8. Distinguish between the following pairs of terms. a. Cytokinesis and mitosis b. Prophase I and Prophase II c. Diploid and haploid d. Gamete and zygote e. Fertilisation and meiosis f. Somatic cells and gametes 9. If a woman has already given birth to three boys, what are the chances of her next child being a girl? Justify your response. 10. A few genetic traits, such as hairiness in ears, are due to genes carried on the Y chromosome. Would males and females have the same chance of having the trait? Justify your response. 11. Figures a. to d. show bluebell cells in various stages of mitosis. a. Suggest which order they should be placed in. b. Describe what is happening at each stage of mitosis. 12. SIS Using the following table, suggest the possible effect of increasing global temperatures on turtles, crocodiles and lizards. TABLE Temperature control of sex in some reptiles Reptile Cold 20–27 °C Warm 28–29 °C Hot > 30 °C Male Male or female Female Crocodile Female Male Female Lizard Female Male or female Male Turtle Evaluate and create 13. The kind of job a man does can affect whether he produces more or less Y sperm or any sperm at all. Chemicals and hormones washed into waterways or used in producing food can affect fertility. Research an example of an environmental impact on fertility and report your findings. Make sure you quote the sources of your information. 14. In many cultures throughout history, a woman has been blamed for not producing sons and has been divorced. From a biological point of view, could this be justified? Explain your answer. 15. Copy and complete the following Venn diagram, choosing from the following terms: somatic, only, body, gonads, gametes, anywhere, different, identical, chromosomes, cell division, eukaryotes. 16. The Y chromosomes of human males are shorter than the X chromosomes. Would the same number of genes be carried by both chromosomes? Justify your response with clear examples. 17. SIS a. How many sets of chromosomes do you think an organism would have if it was identified as 4n and tetraploid? b. Outline an investigation you may conduct to determine if an organism is tetraploid. 18. a. Create a model to allow you to describe each stage of meiosis. b. Explain why interphase only occurs before meiosis I and not meiosis II. Fully worked solutions and sample responses are available in your digital formats.