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Unit 1: What is Biology? Unit 2: Ecology Unit 3: The Life of a Cell Unit 4: Genetics Unit 5: Change Through Time Unit 6: Viruses, Bacteria, Protists, and Fungi Unit 7: Plants Unit 8: Invertebrates Unit 9: Vertebrates Unit 10: The Human Body Unit 1: What is Biology? Chapter 1: Biology: The Study of Life Unit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and Conservation Unit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell Unit 4: Genetics Chapter 10: Mendel and Meiosis Chapter 11: DNA and Genes Chapter 12: Patterns of Heredity and Human Genetics Chapter 13: Genetic Technology Unit 5: Change Through Time Chapter 14: The History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity Unit 6: Viruses, Bacteria, Protists, and Fungi Chapter 18: Viruses and Bacteria Chapter 19: Protists Chapter 20: Fungi Unit 7: Plants Chapter 21: Chapter 22: Chapter 23: Chapter 24: What Is a Plant? The Diversity of Plants Plant Structure and Function Reproduction in Plants Unit 8: Invertebrates Chapter 25: What Is an Animal? Chapter 26: Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27: Mollusks and Segmented Worms Chapter 28: Arthropods Chapter 29: Echinoderms and Invertebrate Chordates Unit 9: Vertebrates Chapter 30: Fishes and Amphibians Chapter 31: Reptiles and Birds Chapter 32: Mammals Chapter 33: Animal Behavior Unit 10: The Human Body Chapter 34: Protection, Support, and Locomotion Chapter 35: The Digestive and Endocrine Systems Chapter 36: The Nervous System Chapter 37: Respiration, Circulation, and Excretion Chapter 38: Reproduction and Development Chapter 39: Immunity from Disease Plants What is a Plant? The Diversity of Plants Plant Structure and Function Reproduction in Plants Chapter 24 Introduction: Reproduction in Plants 24.1: Life Cycles of Mosses, Ferns, and Conifers 24.1: Section Check 24.2: Flowers and Flowering 24.2: Section Check 24.3: The Life Cycle of a Flowering Plant 24.3: Section Check Chapter 24 Summary Chapter 24 Assessment What You’ll Learn You will compare and contrast the life cycles of mosses, ferns, and conifers. You will sequence the life cycle of a flowering plant. You will describe the characteristics of flowers, seeds and fruits. Section Objectives: • Review the steps of alternation of generations. Section Objectives: • Survey and identify methods of reproduction and the life cycles of mosses, ferns, and conifers. Alternation of Generations • An alternation of generations consists of a sporophyte stage and a gametophyte stage. • All cells of a sporophyte are diploid. • Certain cells of a sporophyte undergo meiosis, which produces haploid spores. Alternation of Generations • These spores undergo cell divisions and form a multicellular, haploid gametophyte. Alternation of Generations • The female gamete is an egg and the male is a sperm. • When a sperm fertilizes an egg, a diploid zygote forms. This is sexual reproduction. • If the embryo develops to maturity, the cycle can begin again. Alternation of Generations • This basic life cycle pattern is the same for most plants. However, there are many variations on this pattern within the plant kingdom. • Most people have never even seen the female gametophyte of a flowering plant. • Botanists usually refer to the bigger, more obvious plant as the dominant generation. Alternation of Generations • The dominant generation lives longer and can survive independently of the other generation. Dominant generation Asexual reproduction • Most plants also can reproduce asexually by a process called vegetative reproduction. • In this type of reproduction, new plants are produced from existing plant organs or parts of organs. • The new plants have the same genetic makeup as the original plant. Asexual reproduction • The new plants have the same genetic makeup as the original plant. Life Cycle of Mosses • The gametophyte stage is the dominant generation in mosses. • A haploid moss spore can germinate and grow to form a protonema (proh tuh NEE muh). It is a small green filament of cells that can develop into the gametophyte. Life Cycle of Mosses Mitosis Developing sporophyte Sporophyte (2n) Zygote (2n) Sperm Gametophyte (n) Fertilization Meiosis SPOROPHYTE GENERATION 2n Egg GAMETOPHYTE GENERATION n Male gametophyte (n) Capsule Female gametophyte (n) Capsule opens releasing spores Germinating spores Protonema Life Cycle of Mosses • Some moss gametophytes also reproduce by vegetative reproduction. • They can break into pieces when dry and brittle then, when moisture returns, each piece can grow and form a protonema then a gametophyte. Life Cycle of Ferns • Unlike mosses, the dominant stage of the fern life cycle is the sporophyte stage. • The fern sporophyte includes the familiar fronds. • On the underside of some fronds are sori, which are clusters of sporangia. Life Cycle of Ferns • Meiosis occurs within the sporangia, producing haploid spores. Life Cycle of Ferns • A spore can germinate to form a heart-shaped gametophyte called a prothallus • The prothallus produces both archegonia and antheridia on its surface. Prothallus Archegonium Antheridium Life Cycle of Ferns • The flagellated sperm released by antheridia swim through a film of water to eggs in archegonia. If fertilization occurs, the diploid zygote can develop into the sporophyte. • Once the sporophyte produces green fronds, it can carry on photosynthesis and survive on its own. Life Cycle of Ferns Click image to view movie. Life Cycle of Ferns • The mature fern sporophyte consists of a rhizome from which roots and fronds grow. Fronds Rhizome Roots Life Cycle of Ferns Growing prothallus Spores (n) Prothallus Archegonium Antheridium Egg Rhizoids Meiosis Sporangium Sorus GAMETOPHYTE Sperm GENERATION n Fertilization SPOROPHYTE GENERATION Zygote 2n Fronds Rhizome Roots Cell divisions The Life Cycle of Conifers • The dominant stage in conifers is the sporophyte generation. • The adult conifer produces male and female cones on separate branches of one plant. • Cones contain sporeproducing structures, or sporangia, on their scales. The Life Cycle of Conifers • Female cones, which are larger than the male cones, develop two ovules on the upper surface of each cone scale. • A megaspore is a female spore that eventually becomes the female gametophyte. The Life Cycle of Conifers • Male cones have sporangia that undergo meiosis to produce male spores called microspores. • Each microspore can develop into a male gametophyte, or pollen grain. The Life Cycle of Conifers • In conifers, pollination is the transfer of pollen grains from the male cone to the female cone. Egg Pollen grain Micropyle The Life Cycle of Conifers • The opening of the ovule is called the micropyle (MI kruh pile). • The pollen grain adheres to a sticky drop of fluid that covers the micropyle. As the fluid evaporates, the pollen grain is drawn closer to the micropyle. The Life Cycle of Conifers • Although pollination has occurred, fertilization does not take place for at least a year. • As the pollen grain matures, it produces a pollen tube that grows through the micropyle and into the ovule. The Life Cycle of Conifers • A sperm nucleus from the male gametophyte moves through the pollen tube to the egg. • If fertilization occurs, a zygote forms. • A seed coat forms around the ovule as the mature seed is produced. Mature seed are released when the female cone opens. The Life Cycle of Conifers Female cone Ovule Megaspores Male cone Microspores Young seedling Adult sporophyte Microspore mother cell Meiosis SPOTOPHYTE GENERATION 2n Seed Male gametophyte (pollen grain) Two archegonia with egg cells GAMETOPHYTE GENERATION n Fertilization Seed coat Sperm nucleus Cotyledons Embryo Female gametophyte Stored food One egg is fertilized Egg Pollen grain Maturing pollen Micropyle grain The Life Cycle of Conifers Click image to view movie. Question 1 Which of the following is NOT true of gemmae? (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) A. They are an example of vegetative reproduction. B. They have the same genetic makeup as the original plant. C. They are diploid. D. They are structures of liverworts. The answer is C. Gemmae are haploid. Question 2 TX Obj 2; 4B, 8C, 10A, 10B, TX Mitosis Developing sporophyte Sporophyte (2n) Zygote (2n) Sperm Gametophyte (n) Fertilization Meiosis SPOROPHYTE GENERATION 2n Egg GAMETOPHYTE GENERATION n Male gametophyte (n) Capsule Female gametophyte (n) Capsule opens releasing spores Germinating spores Protonema Obj 3; 13A This figure represents mosses because it reveals a dominant gametophyte generation and displays the presence of a protonema. Question 3 A prothallus is a structure belonging to _______. (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) A. ferns B. liverworts C. conifers D. mosses The answer is A, ferns. Section Objectives: • Identify the organs of a flower. • Examine how photoperiodism influences flowering. What is a flower? • The process of sexual reproduction in flowering plants takes place in a flower, which is a complex structure made up of several organs. The structure of a flower • A flower’s structure is genetically determined and usually made up of four kinds of organs: sepals, petals, stamens, and pistils. The structure of a flower • Petals are usually the colorful structures at the top of a flower stem. • The flower stem is called peduncle. • Sepals are usually leaf-like and encircle the peduncle below the petals. The structure of a flower • Inside the petals are the stamens. A stamen is the male reproductive organ of a flower. • At the tip of the stamen is the anther. The anther produces pollen that eventually contains sperm. The structure of a flower Stigma Petals Style Ovary Anther Stamen Filament Sepal Peduncle Pistil The structure of a flower • The pistil is the female organ of the flower. • The bottom portion of the pistil is the ovary, a structure with one or more ovules, each usually contains one egg. Modifications in flower structure • A flower that has all four organs—sepals, petals, stamens, and pistils—is called a complete flower. Modifications in flower structure • A flower that lacks one or more organs is called an incomplete flower. • For example the flowers of plants such as sweet corn, and grasses, have no petals and are adapted for pollination by wind rather than by animals. Photoperiodism • The relative lengths of daylight and darkness each day have a significant effect on the rate of growth and the timing of flower production in many species of flowering plants. • The response of flowering plants to daily daylight-darkness conditions is called photoperiodism. Photoperiodism • Plant biologists originally thought that the length of daylight controlled flowering. • However, they now know that it is the length of darkness that controls flowering, and that the darkness must be uninterrupted. Photoperiodism • Plants are short-day plants, long-day plants, day-neutral plants, or intermediate day plants. • A short-day plant flowers when the number of daylight hours is shorter than that of its critical period. Photoperiodism • Short-day plants usually flower sometime during late summer, fall, winter, or spring. Photoperiodism • A long-day plant flowers when the number of daylight hours is longer than that of its critical period. • Long-day plants usually flower in summer, but also will flower if lighted continually. Photoperiodism • Some plants will flower over a range in the number of day-light hours. These plants are called day-neutral plants. • An intermediate-day plant will not flower if days are shorter or longer than its critical period. Photoperiodism • Photoperiodism is a physioloical adaptation of all flowering plants that ensures the production of flowers at a time when there is an abundant population of pollinators. Question 1 In flowers, the _______ receives the pollen. (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) A. peduncle B. sepal C. stigma D. anther The answer is C, stigma. Stigma Petals Style Ovary Anther Stamen Filament Sepal Peduncle Pistil Question 2 Plants that flower year-round are most likely to be _______. (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) A. B. C. D. short-day plants long-day plants intermediate-day plants day-neutral plants The answer is D, day-neutral plants. Question 3 The _______ encircle the peduncle below the petals. (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) A. stamens B. anthers C. sepals D. styles The answer is C, sepals. Stigma Petals Style Ovary Anther Stamen Filament Sepal Peduncle Pistil Section Objectives: • Survey and identify the methods of reproduction, growth, and development in flowering plants. • Outline the processes in which cells differentiate during the formation of seeds and fruits and during seed germination. The Life Cycle of an Anthophyte • The life cycle of flowering plants is similar to that of conifers in many ways. Pollen sac with microspore mother cells Microspores in fours Pollen grain Meiosis Anther Ovule with megaspore mother cell Sperm Four megaspores Egg Tube nucleus Pollen tube GAMETOPHYTE Female gametophyte GENERATION n Fertilization Adult sporophyte plant Young seedling SPOROPHYTE GENERATION 2n Double fertilization Male gametophyte Ovary Pollen tube Zygote Endosperm nucleus Germinating seed Seed Fruit with seeds The Life Cycle of an Anthophyte Development of the female gametophyte • In anthophytes, the female gametophyte is formed inside the ovule within the ovary. • In the ovule, a cell undergoes meiosis and produces haploid megaspores. • In most flowering plants, the megaspore’s nucleus undergoes mitosis three times, producing eight haploid nuclei. Development of the female gametophyte • These eight nuclei make up the female gametophye. Cell walls form around each of six nuclei, one of which is now called the egg cell. • The two remaining nuclei, which are called polar nuclei, are enclosed in one cell. • This cell, the central cell, is located at the center of the female gametophyte. Development of the female gametophyte Embryo sac (female gametophyte) • The other five cells eventually disintegrate. Central cell Ovule Egg cell Micropyle Development of the male gametophyte • Haploid microspores are produced by meiosis within the pollen sac. • The nucleus of each microspore undergoes mitosis. • A thick, protective wall surrounds these two nuclei. This structure is the immature male gametophyte, or pollen grain. Development of the male gametophyte • When the pollen grains mature, the anther usually splits open. Pollen sacs Microspore mother cell (2n) MEIOSIS Generative nucleus Tube nucleus ANTHER Pollen grain (male gametophyte) Microspores (n) Pollination • In anthophytes, pollination is the transfer of the pollen grain from the anther to the stigma. • Depending on the type of flower, the pollen can be carried to the stigma by wind, water, or animals. • Most anthophytes that are pollinated by animals produce nectar in their flowers. Pollination • Nectar is a liquid made up of proteins and sugars and usually collects in the cuplike area at the base of petals. • Animals, such as insects and birds, brush up against the anthers while trying to get to the nectar. Pollination • The pollen that attaches to them can be carried to another flower, resulting in pollination. Pollination • Some of the bright, vivid flowers attract pollinators, such as butterflies and bees. Pollination • Flowers that are pollinated by beetles and flies have a strong scent but are often dull in color. • Many flowers have structural adaptations that favor cross-pollination—pollination between two plants of the same species. • This results in greater genetic variation because a sperm from one plant fertilizes an egg from another. Fertilization • Inside each pollen grain are two haploid nuclei, the tube nucleus and the generative nucleus. Stigma Style Pollen grain Two sperm nuclei Pollen tube Tube nucleus Ovary Central cell Ovule Egg cell Fertilization • The tube nucleus directs the growth of the pollen tube down through the pistil to the ovary. • The generative nucleus divides by mitosis, producing two sperm nuclei. Fertilization • The sperm nuclei move through the pollen tube to a tiny opening in the ovule called the micropyle. Pollen grain Stigma Style Two sperm nuclei Pollen tube Tube nucleus Ovary Central cell Ovule Egg cell Fertilization Double Fertilization • One of the sperm unites with the egg forming a diploid zygote, which begins the new sporophyte generation. • The other sperm nucleus fuses with the central cell, which contains the polar nuclei, to form a cell with a triploid (3n) nucleus. One sperm fertilizes the egg cell (2n) One sperm fertilizes the central cell (3n) Fertilization • This process, in which one sperm fertilizes the egg and the other sperm joins with the central cell, is called double fertilization. • The triploid nucleus will divide many times, eventually forming the endosperm of the seed. • The endosperm is food storage tissue that supports development of the embroyo in anthophyte seeds. Seeds and Fruits Fruit Ovary Ovules Sepals Stamen Fused petals Seed formation • After fertilization takes place, seed development begins. • Inside the ovule, the zygote divides and develops into the embryo plant. • The triploid central cell develops into the seed’s endosperm. Seed formation • The wall of the ovule becomes the seed coat, which can aid in seed dispersal and help protect the embryo until it begins growing. Seed formation Click image to view movie. Fruit formation • As the seeds develop, the surrounding ovary enlarges and becomes the fruit. • A fruit is the structure that contains the seeds of an anthophyte. • A fruit is as unique to an anthophyte as is its flower, and many anthophytes can be identified by examining their fruits. Fruit formation • Some plant foods that we call vegetables or grains are actually fruits. • For example, green peppers are fleshy fruits that are often referred to as vegetables. Fruit formation Click image to view movie. Seed dispersal • The dispersal of seeds is important because it reduces competition for sunlight, soil, and water between the parent plant and its offspring. • Animals such as raccoons, deer, bears, and birds help distribute many seeds by eating fruits. Seed dispersal • Seeds that are eaten usually pass through the digestive system undamaged and are deposited in the animal’s wastes. • Plants that grow in or near water, produce fruits or seeds with air pockets in the walls that enable them to float and drift away from the parent plant. Seed dispersal • The ripened fruits of many plants split open to release seeds with structural adaptations for dispersal by wind or by clinging to animal fur. Seed germination • At maturity, seeds are fully formed. • The seed coat dries and hardens, enabling the seed to survive environmental conditions that are unfavorable to the parent plant. • The seeds of some plant species must germinate within a short period of time or die. Seed germination • The seeds of some plant species can remain in the soil until conditions are favorable for growth and development of the new plant. • This period of inactivity in a mature seed is called dormancy. The length of time a seed remains dormant can vary from one species to another. Seed germination • Even under harsh conditions, the seeds of desert wildflowers and some conifers can survive dormant periods of 15 to 20 years. Requirements for germination • Germination is the beginning of the development of the embryo into a new plant. Requirements for germination • Water is important because it activates the embryo’s metabolic system. • Once metabolism has begun, the seed must continue to receive water or it will die. • Just before the seed coat breaks open, the rate of respiration in the plant embryo increases rapidly. • Some seeds have specific requirements for germination. Requirements for germination • For example, some germinate more readily after they have passed through the acid environment of an animal’s digestive system. • The seeds of some conifers will not germinate unless they have been exposed to fire. Requirements for germination • Once the seed coat has been softened by water, the embryo starts to emerge from the seed. • The first part of the embryo to appear is the embryonic root called the radicle (RA dih kul). Radicle Seed coat Requirements for germination • The radicle grows down into the soil and develops into a root. • The portion of the stem nearest the seed is called the hypocotyl (HI poh kah tul). Cotyledon Seed coat Hypocotyl Primary root Requirements for germination • As the hypocotyl continues growing, it straightens, bringing with it the cotyledons and the plant’s first leaves. Cotyledon Secondary roots Requirements for germination • In monocots, the cotyledon remains below the soil’s surface. As growth continues, the leaves turn green, and the plant produces its own food through photosynthesis. Epicotyl Withered cotyledons Hypocotyl Secondary roots Vegetative reproduction • The roots, stems, and leaves of plants are called vegetative structures. • When these structures produce a new plant, it is called vegetative reproduction. Vegetative reproduction • Some modified stems of anthophytes, such as potato tubers, can produce a new plant from each “eye” or bud. • Using vegetative reproduction to grow numerous plants from one plant is frequently referred to as vegetative propagation. Vegetative reproduction • Even smaller pieces of plants can be used to grow plants by tissue culture. • Pieces of plant meristematic tissue are placed on nutrient agar in test tubes or petri dishes. Vegetative reproduction • The plants grown from cuttings and tissue cultures have the same genetic makeup as the plants from which they came and are botanical clones. • There is great diversity in the flowers, seeds, fruits, and vegetative structures of anthophytes. • Anthophytes are divided into families based on these differences. Cocoa Sterculiaceae Magnolia Cactuc Cactaceae Caraway Apiaceae Magnoliaceae Chicory Asteraceae Milkweed Coleus Asclepiadaceae Oak Fagaceae Lamiaceae Raspberry Rosaceae Palm Dicots Arecaceae Lily Grass Liliaceae Monocots Poaceae Orchid Orchidaceae Protists Question 1 Most anthophytes that produce nectar are pollinated by _______. (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) A. wind B. animals C. water D. machines The answer is B, animals. Question 2 In anthophytes, _______ is the transfer of immature male gametophytes from the anther to the stigma. (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) A. double fertilization B. germination C. pollination D. vegetative reproduction The answer is C, pollination. Question 3 Why can insects see some flower marking that humans cannot see? (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) Many of these flower markings are visible only to organisms, like insects, that can detect ultraviolet light. The human eye cannot detect ultraviolet light. Question 4 What is the difference between the functions of a tube nucleus and a generative nucleus? (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) Answer The tube nucleus directs the growth of the pollen tube down through the pistil to the ovary. The generative nucleus divides by mitosis, producing two sperm nuclei. Life Cycles of Mosses, Ferns, and Conifers • The gametophyte generation is dominant in mosses. Archegonia and antheridia form on separate or the same gametophyte. Fertilization requires a film of water on the gametophyte. • Archegonia and antheridia develop on a prothallus, the fern gametophyte. Fertilization requires a film of water on the gametophyte. The sporophyte generation is dominant in ferns. Life Cycles of Mosses, Ferns, and Conifers • Conifers have cones in which a male or female gametophyte forms. Sperm nuclei form in pollen grains and eggs form in ovules. The embryo is protected in a seed. Flowers and Flowering • Flowers are made up of four organs: sepals, petals, stamens, and pistils. A flower lacking any organ is called incomplete. Complete flowers have all four organs. • Photoperiodism—responses of flowering plants to daylight-darkness conditions affects flower production. Plants are called short-day, longday, day-neutral, or intermediate depending upon their photoperiodic response. The Life Cycle of a Flowering Plant • The male gametophyte develops from a microspore in the anther. The female gametophyte develops from a megaspore in the ovule. • Double fertilization occurs when a sperm nucleus joins with an egg to form a zygote. The second sperm nucleus joins the central cell to form endosperm. The Life Cycle of a Flowering Plant • Fruits and seeds are modified for dispersal. Seeds can stay dormant for a long time before they germinate. Question 1 During the life cycle of conifers, microspores develop into _______. (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) A. archegonia B. micropyles C. megaspores D. pollen grains The answer is D, pollen grains. Question 2 How is photoperiodism associated with pollination? (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) Answer Photoperiodism is a physiological adaptation of all flowering plants that ensure the production of flowers at a time when there is an abundant population of pollinators. Question 3 The process whereby one sperm fertilizes the egg and the other sperm joins with the central cell is called _______. (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) A. photoperiodism B. vegetative reproduction C. double fertilization D. germination Double Fertilization The answer is C, double fertilization. One sperm fertilizes the central cell (3n) One sperm fertilizes the egg cell (2n) Question 4 The _______ is the structure that contains the seed of an anthophyte. (TX Obj 2; 4B, 8C, 10A, 10B, TX Obj 3; 13A) A. fruit B. stamen C. ovule D. egg cell The answer is A, fruit. Question 5 Food storage tissue that supports development of the embryo in anthophyte seeds is the _______. (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) A. megaspore B. microspore C. endosperm D. ovule The answer is C, microspore. Question 6 The dormancy period of a seed ends with _______. (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) A. fertilization B. germination C. pollination D. dispersal The answer is B, germination. Question 7 The radicle of a plant embryo develops into a _______. (TX Obj 2; 4B, 8C, 10A, 10B TX Obj 3; 13A) A. stem B. pair of leaves C. cotyledon D. root The answer is D, root. Question 8 What pushes a seedling upward through the soil when it emerges from its seed? (TX Obj 2; 4B, 8C, TX Obj 3; 13A TX Obj 4, 7A) Answer This push or force results from water pressure inside the seedling’s cells. Question 9 A flower that naturally has four petals, eight stamens, and one pistil is an example of a (n) _______. (TX Obj 2, 8C, 10A, 10B TX Obj 3; 13A) A. dicot B. incomplete flower C. monocot D. male flower The answer is A, dicot. Question 10 In flowering plants, _______ begins the sporophyte generation. (TX Obj 2, 8C, 10A, 10B TX Obj 3; 13A) A. meiosis B. germination C. fertilization D. pollination The answer is C, fertilization. Photo Credits • National Cotton Council of America • PhotoDisc • Photo Essentials • Matt Meadows • Digital Stock • USDA • Corbis • Alton Biggs To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents Click on this icon to return to the previous slide Click on this icon to move to the next slide Click on this icon to open the resources file. End of Chapter 24 Show