1. Answers will vary but should include the noted variety in the sexual world, along with the general increase in population.
2. See pages 192-193.
3. The number of individuals remains the same.
4. These terms are defined in text.
5. Numerous answers are possible. The major similarity is that both produce gametes. For specific physical similarities, see pages 196 and 197.
6a. Oogonium - 2
b. Primary spermatocyte - 2
c. Spermatid -1
d. Secondary oocyte -1
e. Polar body from primary oocyte - 2
7a. Asexual - parthenogenesis
b. Asexual - binary fission
c. Asexual - cutting
d. Sexual
8. Gametes are haploid to preserve the diploid number.
9. The human oocyte rids itself of excess genetic material by forming polar bodies. The excess cytoplasm in the human sperm falls away during maturation.
10. Male gametogenesis takes 74 days. Female gametogenesis technically varies with the oogonium. The process begins before birth and, with any given oogonium, is not complete until the egg is fertilized -- from 10 to 50 years later.
TO THINK ABOUT
1. Considering independent assortment only, the possible number of pups would be 239 or 5.4976 x 1011 but statistically this is an overestimation. The dogs could not produce this many offspring. In addition, the probability of a repeat occurs before the probability that each of the 239 events would occur.
2. The sperm must travel through the vas deferentia.
3. Simple statistics. For a "normal" scenario, if both parents had one (haploid) set of identical chromosomes, it would be theoretically possible for the child to inherit exactly the right chromosomes for this genetic identical-ness. For any other scenario, an abnormal situation would have to develop. For instance, if the primary oocyte (diploid) were fertilized but the chromosomes of the sperm (haploid) were inactivated, the child would be genetically identical to the mother. Or if humans developed the ability to be parthenogenic, the child would be identical to the mother. This latter example could be an outgrowth of the induced parthenogenesis alluded to in the opening vignette.
4. Sperm stem cells.
5. Nutrient material and necessary organelles are missing.
6. Answers will vary. See page 204.
7. Primary spermatocytes are diploid; spermatids are haploid.
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