. Advanced biology. Biology; Physiology; Reproduction. DIFFERENCES AMONG OFFSPRING 315 or poor nutrition or toxic materials of one sort or another. Only by affecting germ cells can the character of the offspring be con- trolled or changed. Recently, it has been demonstrated that in- ternal secretions circulating in the blood of the parent may affect the germ cells. Thus, if a mother's thyroid is overactive and too much thyroxin circulates in the blood, the germ cell may be affected in such a way that abnormalities in the developing off- spring are frequently brought about. Differences among of

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. Advanced biology. Biology; Physiology; Reproduction. DIFFERENCES AMONG OFFSPRING 315 or poor nutrition or toxic materials of one sort or another. Only by affecting germ cells can the character of the offspring be con- trolled or changed. Recently, it has been demonstrated that in- ternal secretions circulating in the blood of the parent may affect the germ cells. Thus, if a mother's thyroid is overactive and too much thyroxin circulates in the blood, the germ cell may be affected in such a way that abnormalities in the developing off- spring are frequently brought about. Differences among of Stock Photo
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. Advanced biology. Biology; Physiology; Reproduction. DIFFERENCES AMONG OFFSPRING 315 or poor nutrition or toxic materials of one sort or another. Only by affecting germ cells can the character of the offspring be con- trolled or changed. Recently, it has been demonstrated that in- ternal secretions circulating in the blood of the parent may affect the germ cells. Thus, if a mother's thyroid is overactive and too much thyroxin circulates in the blood, the germ cell may be affected in such a way that abnormalities in the developing off- spring are frequently brought about. Differences among of
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. Advanced biology. Biology; Physiology; Reproduction. DIFFERENCES AMONG OFFSPRING 315 or poor nutrition or toxic materials of one sort or another. Only by affecting germ cells can the character of the offspring be con- trolled or changed. Recently, it has been demonstrated that in- ternal secretions circulating in the blood of the parent may affect the germ cells. Thus, if a mother's thyroid is overactive and too much thyroxin circulates in the blood, the germ cell may be affected in such a way that abnormalities in the developing off- spring are frequently brought about. Differences among offspring. It has long been known that certain characteristics or qualities reappear in successive genera- tions. Why do not all the characteristics of the parents reappear ? If each new individual were merely a portion of an older individual, it could readilv be seen how the characters would continue from one generation to the next. When plants are propagated by cuttings or by grafts, the plants thus produced remain rather uniform. Where reproduction is sexual, two germ cells, the gametes, come from different sources. Each germ cell carries many qual- ities that are characteristic of the protoplasm of each parent. These qualities reappear with a certain degree of probability and in relationship after the two germ cells have united. Each individual resembles both parents, but, necessarily, also differs from both. When two coins are tossed a great number of times, two tails turn up 25^7 of the times, two heads turn up 25'i of the times and one head and one tail turn up SO"^, of the time. This occurrence is called the law of chance. In the few matchings shown in the diagram, the result would prob- ably not be as near the 25,50,25 ratio as is pictured. This illustrates the law of chance (page 317). parents. A child may have brown eyes like the mother's and curly hair like the father's. Offspring of the same parents also differ. Please note that these images are extracted from s

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