Understanding Sexual Reproduction

Transcription

1 Lesson A3-1: Understanding Sexual Reproduction Horticulture Cluster Illinois Agricultural Education Core Curriculum Unit A. Horticultural Science Problem Area 3. Plant Propagation Lesson 1. Understanding Sexual Reproduction Illinois State Goal and Learning Standard. This lesson is correlated to the following State Goal and Learning Standard: State Goal 12: Understand the fundamental concepts, principles and interconnections of the life, physical and earth/space sciences. Learning Standard A: Know and apply concepts that explain how living things function, adapt and change. Learning Benchmark 4B: Describe the structures and organization of cells and tissues that underlie basic life function including nutrition, respiration, cellular transport, biosynthesis and reproduction. Skill Standard GN9: Propagate and grow plants. Student Learning Objectives. Instruction in this lesson should result in students achieving the following objectives: 1. Discuss the importance of plant propagation. 2. Explain the difference between sexual and asexual propagation. 3. Identify the major parts of a seed. 4. List the function of each major part of a seed. Unit A. Problem Area 3. Lesson 1. Page 1.

2 List of Resources. The following resources may be useful in teaching this lesson: Recommended Resources. One of the following resources should be selected to accompany the lesson: Seagle, Eddie Dean, et al. Introduction to Horticulture. Danville, Illinois: Interstate Publishers, Inc., 2000 (Textbook and Activity Manual Chapter 5). Reiley, H. Edwards and Carroll L. Shry. Jr. Introductory Horticulture. Albany, New York: Delmar Publishers Inc., 1996 (Textbook and Laboratory Manuel Unit 6). Other Resources. The following resources will be useful to students and teachers: Ball, Vic. Ball RedBook. West Chicago, Illinois: Geo. J. Ball Publishing, (Chapter 21) Biondo, Ronald J. and Jasper S. Lee. Introduction to Plant and Soil Science and Technology. Danville, Illinois: Interstate Publishers, Inc., 1997 (Textbook and Activity Manual, Chapter 4). Boodley, James W. The Commercial Greenhouse. Albany, New York: Delmar Publishers Inc., 1998 (Chapter 17). Ingels, Jack E. Ornamental Horticulture. Albany, New York: Delmar Publishers Inc.,1994. Hill, Lewis. Secrets of Plant Propagation. Pownal, Vermont: Garden Way Publishing, 1985 (Chapter 2). List of Equipment, Tools, Supplies, and Facilities Writing surface Overhead projector Transparencies from attached masters Terms. The following terms are presented in this lesson (shown in bold italics): Cotyledon Cross pollination Diploid Embryo Endosperm Epicotyl (plumule) Fertilization Gametes Genes Haploid Hybrids Unit A. Problem Area 3. Lesson 1. Page 2.

3 Hypocotyl Pollination Radicle Seed Seed coat Self pollination Sexual reproduction Zygote Interest Approach. Use an interest approach that will prepare the students for the lesson. Teachers often develop approaches for their unique class and student situations. A possible approach is included here. Bring samples of various flowering plants to class. Also bring samples of several non flowering foliage plants that are propagated asexually. Display them to students and ask them what they think the value of the flower is to the plant? How are plants more successful at reproduction than animals? After a few minutes of discussion, move on to the lesson content. Summary of Content and Teaching Strategies Objective 1: Discuss the importance of plant propagation. Anticipated Problem: What would happen if plants did not have the ability to reproduce? I. Plants are essential for life as we know it on earth. A. Plants are the ecological producers of our planet. They provide food and shelter for other organisms, produce oxygen to support animal respiration, and enrich our environment. B. Throughout history people have relied on seeds and plant parts to grow new plants for food and fiber. C. In more recent times, knowledge of plant reproduction has resulted in the development of plant hybrids that have enabled large scale agricultural production of food and fiber plants. Use TM: A3-1A to help illustrate the importance of plants to the human diet. Use TM: A3-1B and TM: A3-1C to help students understand the amount of food and fiber plants that are produced worldwide to support the human population on earth today. Discuss the issue of food production and global starvation. Be open to related topics of discussion that may arise i.e. genetic manipulation of food crop plants. Unit A. Problem Area 3. Lesson 1. Page 3.

4 Objective 2: Explain the difference between sexual and asexual propagation. Anticipated Problem: How is sexual reproduction different from asexual reproduction and what is the advantage of sexual reproduction? II. Sexual reproduction occurs when the male sperm carried in the pollen unites with the female egg within a flower. A. Most plants reproduce their own kind in nature by seeds that are the result of sexual reproduction. The male sex cell (sperm) and the female sex cell (egg) are known as gametes. The union of the gametes produces the seed that contains the embryo plant and stored food. B. Both the male sperm and female egg contribute genetic information to the new embryo plant. The union of sperm and egg results in new combinations of genetic information. These combinations produce new traits that add to the vigor of the offspring. C. The offspring that result from this new combination of genes are known as hybrids. People have greatly improved agricultural crops through hundreds of years of hybridization. D. The genes (Deoxyribonuclei acid) are located in chromosomes. Normal plant cells contain a pair of chromosomes and are said to be diploid. Reproductive cells, the egg and the sperm, contain a single chromosome and are said to be haploid. E. Fertilization unites the single chromosome in the sperm nucleus with the single chromosome in the egg nucleus. This enables the fertilized egg or zygote to have a complete pair of chromosomes (diploid). F. Pollination is the transfer of the male sperm carried in the pollen to the female part of the flower, the stigma. Plants rely on wind and water to transfer the pollen to the stigma. In addition, plants depend on animals to help with pollination. Birds, insects, bats and other animals are attracted to brightly colored, scented flowers. These animals transfer pollen from the anthers of the flowers they visit to the stigmas of other flowers. G. When the pollen of a plant pollinates a flower on the same plant, it is called self- pollination. Many plants have this ability to self pollinate, others do not. When the pollen of a plant pollinates the flower on another plant of the same species, it is said to be cross-pollination. H. Fertilization occurs when the nucleus of the sperm unites with the nucleus of the egg. Plant fertilization is unique because the sperm contains two nuclei. Flowering plants have a double fertilization. One sperm nucleus unites with the egg nuclei to produce a zygote. The second sperm nucleus unites with the nuclei of the embryo sac that develops into the endosperm. Use TM: A3-1D to discuss the reproductive structures of the parts of the flower. Use TM: A3-1E to illustrate pollination. Discuss agents of pollination. Ask what problems arise from the use of substances in our environment that destroy the Honey bee populations? Use TM: A3-1F to discuss the double fertilization that results from pollination. Unit A. Problem Area 3. Lesson 1. Page 4.

5 Objective 3: Identify the major parts of a seed Anticipated Problem: What are the major parts of a seed and where are they located within the seed? III. A seed is a living entity that serves as a bridge between generations of a plant. It is formed in the pistil of the flower and develops from the ovule following fertilization. As the fertilized egg (zygote) grows and develops, it becomes the embryo of the seed. The zygote grows and develops to become the embryo of the seed. The embryo has the parts (root, stem, leaf) of a complete plant. In addition, the seed contains stored food to support the development and growth of the embryo. This food is stored in the area of the seed known as either the endosperm or the cotyledon. The embryo root is the radicle, the stem is the hypocotyl, and the leaf is the epicotyl. The embryo and endosperm (cotyledon in some plant species) is surrounded by the protective seed coat. Use TM: 3A-1G of the monocot and dicot seed to identify seed structures. Use pre-soaked seeds to examine the parts of the seed. Objective 4: List the function of each major part of a seed. Anticipated Problem: What is the function of each major part of a dicot seed and a monocot seed? IV. Each part of a seed has a specific function to help ensure that a healthy new plant will emerge from the seed. A. The seed is a living entity which contains the embryo plant and everything necessary for its growth and development. Dicot plants (soybean, pea, oak) have two cotyledons or seed leaves in its seed. Monocot plants (corn, coconut, lilies) have one cotyledon in its seed. B. The radicle is the lower end of the hypocotyl that forms the first root of the plant. It is the radicle that emerges from the seed first as germination begins. C. The hypocotyl of the embryo plant develops into the true stem. D. The epicotyl above the hypocotyl develops into a pair of small leaves. The tip of the epicotyl may also be known as the pulmule. The pulmule is the terminal bud of the first shoot to emerge from the seed. E. The endosperm found in monocot plants is an area of high concentration of food which is used as a food source for the embryo plant. F. The cotyledons store food absorbed from the endosperm when the seed was formed. The cotyledon provides the energy that permits the embryo to grow and emerge from the soil so that it can begin to manufacture its own food through photosynthesis. G. The seed coat surrounds the seed and protects it from injury and dehydration. Unit A. Problem Area 3. Lesson 1. Page 5.

6 Use TM: A3-1H of the developing embryo plant to discuss the function of each structural part. Make a master chart to review with the students seed structures and their function. Review/Summary. Focus the review and summary of the lesson around the student learning objectives. Review the diagram of seed structure. Discuss and review the vocabulary of reproduction and the function of each seed structure. Application. Application can involve the following student activity: Students may dissect pre-soaked seeds of corn and lima beans. A hand lens may be used to assist in locating the seed embryo and other seed structures. Evaluation. Evaluation should focus on student achievement of the lesson objectives. Various techniques can be used, such as student performance on the application activities. The self-check section at the end of each chapter in the suggested references will be helpful. A sample written test is attached. Answers to sample test A3-1: Part One: Matching 1. h 2. e 3. c 4. a 5. b 6. f 7. i 8. d 9. g 10. j Part Two: Completion 1. diploid, haploid 2. seed coat 3. embryo 4. cotyledon 5. endosperm Part Three: Short Answer 1. Sexual reproduction gives the plant species the means to change with a changing environment. Every time sexual reproduction occurs there is a recombining of genetic material. Most genetic changes are beneficial because they enable plants to adapt to a changed environment and therefore survive. 2. Pollination occurs when the male pollen is transferred to the female part of the plant. 3. Pollen may be transferred by wind, water or animals to the ovary of the flower where the nuclei of the sperm and egg unite to form a seed that contains the embryo plant. Self-pollination is the pollination of a flower on the same plant. Cross-pollination is the pollination of the flower on another plant. 4. Sexual propagation involves the reproduction of plants with the use of seeds. Asexual propagation is the reproduction of new plants from the stems, leaves or roots of a parent plant. Unit A. Problem Area 3. Lesson 1. Page 6.

7 Sample Test Name Test Lesson A3-1: Understanding Sexual Reproduction Part One: Matching Instructions. Match the term with the correct response. Write the letter of the term by the definition. a. sexual reproduction e. fertilization h. hybrid b. gamete f. zygote i. hypocotyl c. self-pollination g. genes j. epicotyl d. radicle 1. Offspring of genetically different parents. 2. Process within flowering plants that results in a zygote and endosperm. 3. When pollen of a plant pollinates a flower on the same plant. 4. Propagation involving male and female reproductive cells. 5. A male or female reproductive cell. 6. A fertilized egg resulting from the union of nuclei of sperm and egg cells. 7. The embryo plant part that develops into the true stem. 8. The embryo root develops from this structure. 9. The traits inherited from the parent plants are found in these structures. 10. The first leaves develop from this part of the embryo. Part Two: Completion Instructions. Provide the word or words to complete the following statements. 1. Normal cells with a double set of chromosomes are said to be, while those cells with a single set of chromosomes are said to be. 2. The provides a protective shell surrounding the embryo and endosperm. 3. The little plant inside a seed that eventually grows and develops into a mature plant is the. Unit A. Problem Area 3. Lesson 1. Page 7.

8 4. The are the seed leaves of an embryo plant in which food is stored. 5. A monocot seed stores food as a future source of energy in the. Part Three: Short Answer Instructions. Provide information to answer the following questions. 1. Explain the advantage of sexual reproduction. 2. Explain how pollination occurs. 3. Describe how self-pollination and cross-pollination differ. 4. Describe the difference between sexual and asexual propagation. Unit A. Problem Area 3. Lesson 1. Page 8.

9 TM: A3-1A THE IMPORTANCE OF PLANTS IN THE HUMAN DIET Food Guide Pyramid A Guide to Daily Food Choices Fats, Oils, & Sweets USE SPARINGLY Key Fat (naturally Sugars (added) These symbols show fats, oils, and added sugars in food. Milk, Yogurt, & Cheese Group 2-3 SERVINGS Meat, Poultry, Fish, Dry Beans, Eggs, & Nuts Group 2-3 SERVINGS Vegetable Group 3-5 SERVINGS Fruit Group 2-4 SERVINGS Bread, Cereal, Rice & Pasta Group 6-11 SERVINGS (Couresty, USDA) Unit A. Problem Area 3. Lesson 1. Page 9.

10 TM: A3-1B U.S. CROP ACRES HARVESTED, 1993 All Other 16.1% Soybeans 19.0% Hay 20.3% Corn 23.5% Wheat 21.1 Corn*...69,837 Wheat...62,647 Hay...60,398 Soybeans...56,447 Cotton....12,787 Sorghum*... 9,837 Barley...6,791 Oats....3,793 Rice...2,833 Sunflower...2,504 Peanuts...1,637 Dry Edible Beans...1,600 Sugar Beets....1,413 Potatoes...1,317 Sugar Cane Tobacco Rye ,000 ACRES Source: USDA/National Agricultural Statistics Service *Includes harvest for grain and silage Other....47,830 Safflower Flaxseed Canola Dry Edible Peas Lentils Peppermint Oil Sweet Potatoes...79 Hops...43 Spearment Oil...32 Mustard Seed...16 Austrian Winter Peas Rapeseed...6 Unit A. Problem Area 3. Lesson 1. Page 10.

11 TM: A3-1C WORLD CORN EXPORTS* U.S. 59.3% China 22.5% Argentina 9.9% Other 5.6% South Africa 2.7% COUNTRY MILLION METRIC TONS PERCENT United States % China % Argentina % Other % South Africa % Source: Grain: World Markets and Trade, January 3, 1994 USDA Economic Research Service and Foreign Agricultural Serivce *1993/1994 Projected Marketing year data October 1 to September 30 Unit A. Problem Area 3. Lesson 1. Page 11.

12 TM: A3-1D Parts of a Perfect Flower Petal Anther Filament Stamen Stigma Pistil Style Sepal Ovary Receptacle (Couresty, Interstate Publishers, Inc.) Unit A. Problem Area 3. Lesson 1. Page 12.

13 TM: A3-1E POLLINATION Pollen grains (contain sperm) Stigma Ovule Ovary Egg cell (Couresty, Interstate Publishers, Inc.) Unit A. Problem Area 3. Lesson 1. Page 13.

14 TM: A3-1F DOUBLE FERTILIZATION Pollen Stigma 1 Ovary Egg 2 Two sperm nuclei Pollen tube 3 Second nucleus Egg nucleus One sperm fertilizes second nucleus to form endosperm One sperm fertilizes egg (Couresty, Interstate Publishers, Inc.) Unit A. Problem Area 3. Lesson 1. Page 14.

15 TM: A3-1G DICOT VS. MONOCOT SEEDS Epicotyl Two cotyledons Seed coat Endosperm Single cotyledon Epicotyl Embryo Embryo Seed coat Bean Seed Corn Seed (Couresty, Interstate Publishers, Inc.) Unit A. Problem Area 3. Lesson 1. Page 15.

16 TM: A3-1H PARTS OF A DEVELOPING EMBRYO PLANT Epicotyl Cotyledon Hypocotyl Primary Root Secondary Root Primary Root (Couresty, Interstate Publishers, Inc.) Unit A. Problem Area 3. Lesson 1. Page 16.