Unit A Reproduction

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Flowering Plants Most flowers contain both male and female reproductive organs, and so are hermaphrodites. The male reproductive structure is the stamen (Figure 4). The stamen is made of the filament, a stalk that supports the anther. The anther is the top of the stamen and produces pollen. Pollen grains contain the male gametes. There are usually several stamens on each flower. The female reproductive structure is the pistil. The top of the tube-like pistil is the stigma. The sticky stigma receives a pollen grain, which will travel down the tube-like style to the ovary, where the eggs are contained. Surrounding the male and female structures are petals. Petals are the coloured leaf-like structures of most flowers. The organisms that pollinate flowers are attracted to the coloured petals. At the base of the flower, where it joins the stem, are sepals. Sepals are tiny leaf-like structures that protect the flower while it is in the bud stage. 3A petal Investigation stigma style 3A Investigation Examining Flowers To perform this investigation, turn to page 98. In this investigation, you will investigate the structures of several different types of flowers. pistil ovary LEARNING TIP Look closely at Figure 4. Examine each part of the diagram, and check that you understand what it shows. Refer to the words in bold for more information. anther stamen filament sepal Figure 4 Parts of a typical flower In most sexually reproducing organisms, the sperm cells move to the eggs. In flowering plants, the sperm cells are contained in the pollen grains. Pollination, the process by which pollen is moved from the male structures to the female structures, occurs in a variety of ways. Pollen can be moved from the male structure of one flower to the female structure of another flower by wind, insects, birds, or mammals. This is called cross-pollination. Some plants can pollinate themselves. The pollen produced by a flower can pollinate other flowers on the same plant. This is called self-pollination. Fertilization follows pollination. The fertilized egg, or zygote, develops into a seed in the ovary of the flower. GO If you would like to learn more about the parts of a flower, go to www.science.nelson.com GO NEL 3.3 Methods of Sexual Reproduction 85
Figure 5 Male and female cones are found on the same fir tree. The larger female cone contains the developing seeds. Separate Sexes Many complex animals and some plants have separate female and male individuals. The females produce eggs, and the males produce sperm. Not all plants have male and female reproductive structures in the same flower. Conifers, such as pine and fir trees, have separate male and female cones on the same plant (Figure 5). Some species have separate male and female flowers on the same plant. Other species, such as poplar trees, have separate male and female flowers on separate plants. In animals that have separate sexes, there are two methods of fertilization: external fertilization and internal fertilization. If you would like to learn more about a salmon’s life cycle, go to www.science.nelson.com GO External Fertilization In many aquatic animals, such as salmon, the female releases her eggs into the water and the male then releases his sperm over the eggs. Since the sperm and the eggs unite outside the body, this method is called external fertilization (Figure 6). Hundreds or even thousands of eggs and sperm are produced to ensure that enough will unite and grow to be adults. Both the gametes and the developing young are vulnerable to environmental conditions and predators. GO Did You KNOW? Slim Chance of Survival Female salmon lay between 2500 and 7500 eggs in a nest. Because of the many hazards they face, only four or five fertilized eggs from a nest will survive long enough to reproduce. www.science.nelson.com Figure 7 Thousands of coral animals each release an egg to be fertilized. GO (a) Figure 6 After a female sockeye salmon (top) lays eggs in a nest she made in the gravel, the male (bottom) fertilizes the eggs (a). The eggs are fertilized externally when the male releases sperm (seen here as a milky substance) over the eggs (b). 5 mm A spectacular reproductive event occurs in coral reefs. Coral reefs are made of millions of tiny animals, called corals. Each animal builds a hard shell. These shells fuse together to make up a reef. Reproduction occurs when the males and the females both release their eggs and sperm into the ocean at the same time. Fertilization is by chance, as millions of tiny cells fill the water and are carried by the movement of the water (Figure 7). Internal Fertilization Some aquatic animals, such as sharks, and most terrestrial (land) animals, require the sperm from the male to be deposited inside the body of the female. These animals have specialized reproductive structures to accomplish this. (The reproductive structures of humans are discussed in Chapter 4.) Since the union of the sperm and the egg occurs inside the female, this method is called internal fertilization. (b) 86 Unit A Reproduction NEL
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Page 3 and 4: CHAPTER 2 Cell Growth and Reproduct
Page 5 and 6: 2.1 The Importance of Cell Division
Page 7 and 8: 2.1 CHECK YOUR Understanding 1. Giv
Page 9 and 10: Figure 2 Plant cell structures cyto
Page 11 and 12: 2.3 From DNA to Proteins You have l
Page 13 and 14: Did You KNOW? The Human Genome The
Page 15 and 16: LEARNING TIP Think about the sectio
Page 17 and 18: USING MITOCHONDRIAL DNA TO SOLVE MY
Page 19 and 20: centrioles nucleus chromosome spind
Page 21 and 22: 2.4 CHECK YOUR Understanding 1. Wha
Page 23 and 24: LEARNING TIP Make connections to yo
Page 27 and 28: Binary fission allows for rapid pop
Page 29 and 30: 2.6 CHECK YOUR Understanding 1. At
Page 31 and 32: could clone frogs, they were unable
Page 33 and 34: 2A Investigation Observing Cell Div
Page 35 and 36: 2B Investigation Determining the Ra
Page 37 and 38: CHAPTER 2 Review Cell Growth and Re
Page 39 and 40: Review Key Ideas and Vocabulary 1.
Page 41 and 42: CHAPTER 3 Sexual Reproduction KEY I
Page 43 and 44: 3.1 Meiosis LEARNING TIP Scan the t
Page 45 and 46: Interphase Prophase Metaphase Anaph
Page 47 and 48: 3.1 CHECK YOUR Understanding 1. How
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Page 63 and 64: LEARNING TIP Photographs play an im
Page 65 and 66: TRY THIS: A Model of Recombinant DN
Page 67 and 68: 3A Investigation Examining Flowers
Page 69 and 70: 3B Investigation Examining Seeds Re
Page 71 and 72: CHAPTER 3 Review Sexual Reproductio
Page 73 and 74: Review Key Ideas and Vocabulary 1.
Page 75 and 76: CHAPTER 4 Human Reproduction KEY ID
Page 77 and 78: 4.1 The Male Reproductive System LE
Page 79 and 80: LEARNING TIP Did you notice that Se
Page 81 and 82: 4.2 The Female Reproductive System
Page 83 and 84: Depending on whether the egg is fer
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Page 89 and 90: Figure 7 The zygote has divided sev
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Page 93 and 94: Figure 2 The X chromosome (a) is fa
Page 97 and 98: Figure 2 The karyotype of Down synd
Page 99 and 100: 4.6 Prenatal Procedures (a) (b) Fig
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Page 103 and 104: 4.7 Reproductive Technologies LEARN
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4.7 CHECK YOUR Understanding 1. At
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Sample Stakeholder Perspectives •
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CHAPTER 4 Review Human Reproduction
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Review Key Ideas and Vocabulary 1.
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UNIT A Review Reproduction Unit Sum
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15. Complete the following table to
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