Flowers and Reproduction - Botany Reviewer

**Flowers and Reproduction** **Preproduction in Flowering Plants!** ** What are the functions of each part of a flower?** 1. **Sepals -- protect the developing flower. The parts that are usually green and protect the flower bud as it develops. Enclose the bud** 2. **Petals -- The part...

**Flowers and Reproduction** **Preproduction in Flowering Plants!** ** What are the functions of each part of a flower?** 1. **Sepals -- protect the developing flower. The parts that are usually green and protect the flower bud as it develops. Enclose the bud** 2. **Petals -- The parts that attract pollinators** 3. **Stamen: male parts of the flower, producing male gametophytes** - **Anther -- where the sperm cells are produced. The parts that produce pollen (male sex cells), where meiosis takes place.** - **Filament -- supports an anther** 4. **Carpel/Pistils: female parts of the flower, producing female gametophytes** - **Stigma -- collects pollen, a sticky portion where pollen grains frequently lang** - **Style -- carries pollen from the stigma to the ovaries** - **Ovary -- where the eggs are developed. The parts that receive pollen and which contain ovules** **Pedicel - The stalk of the flower** **Receptacle - The end of the stalk, where the other parts are attached** ** Where are eggs and pollen grains formed within the flower?** **Eggs develop in ovules, tiny structures embedded in the ovary at the base of the pistil and pollen grains forms within pollen sacs in anther** ** What is the difference between pollination and fertilization?** **Pollination is transfer of pollen grains through a variety of agents to a receptive stigma. And when a pollen grain lands on the stigma it germinates** **While fertilization is the fusion of gametes after pollination\ ** **Concepts** **Sexual Reproduction in Plants** ** Plants have two stages in their life cycle.** ** A diploid stage alternates with a haploid stage.** ** The diploid plant is called the sporophyte.** ** The haploid plant is called the gametophyte.** **The Plant Life Cycle** **Overview of the Plant Life Cycle** ** Angiosperms alternate between a conspicuous sporophyte (diploid asexual) and a reduced gametophyte (haploid sexual) - alternation of generation** **Alternation of generations** - **a type of life cycle in which subsequent generations of plants alternate between diploid and haploid organisms** **Overview of the Plant Life Cycle** ** For flowering plants, the sporophyte is the dominant, flowering- producing generation.** ***The sporophyte generation*** ** Produces spores that develop within flowers into male gametophytes (pollen grains)** ** Produces female gametophytes (embryo sacs)** **Overview of the Plant Life Cycle** ** The gametophyte generation creates gametes** ** gametes are produced by gametangia** ** gametes are then transferred between plants or spread into the environment.** ** when a gamete encounters a gamete of the opposite sex, it fuses with it to form a zygote which eventually becomes a sporophyte.\ ** **Flowers\ The reproductive structures of angiosperms** ** occurs in response to environmental signals such as day length\ ** **Flowers produce two kinds of spores.\ ** **1. Microspore- Male gametophyte** ** Undergoes mitosis** ** Becomes pollen grain\ ** **2. Megaspore - Female gametophyte** ** Becomes the female gametophyte, an embryo sac within an ovule within an ovary** ** Ovule becomes a seed** ** Ovary becomes a fruit\ ** ** Flower pollen carries sperm to the flower egg in the embryo sac.** **\ Flowers serve several important functions.** ** Production of spores** ** Protection for gametophytes** ** Attraction of pollinators** ** Pollen dispersal\ ** **Flowers** ** Flower parts occur in three\'s (or multiples) in\ monocots.** ** Flower parts occur in four or five\'s (or multiples) in eudicots** **Flower Structure** ***What are the functions of each part of a flower?*** ***\ ***.   ***\ ***   **Classification of Flowers\ ** **Presence or absence of flower parts** ** Complete flower --- has all 4 essential flower parts :petal, sepal, stamen and pistil** ** Incomplete flower --- lacks one or more of the 4 floral parts** ** Perfect flower--- with both the stamen and pistil ( may lack sepal or petal; bisexual flower** ** Imperfect flower --- bears either the stamen or pistil** **- maybe staminate or pistillate** **- unisexual flower** **Dioecious - Flowers are borne on separate plants** **\ **  **Monoecious - Both male and the female flowers are found on the same plant** **Classification of Flowers** **Size and shape of flower parts** ** Regular flower - a flower in which the corolla is made up of similarly-shaped petals equally spaced and radiating from the center of the flower** ** Irregular flower--- a flower in which one or more members of at least one whorl are of different form or size from others\ ** **Where are eggs and pollen grains formed within the flower?** **Pollen** ** forms within pollen sacs in anther** **Each pollen grain contains 2 cells** ** 1 generates two sperm cells** ** 1 produces a pollen tube through which sperm cells reach the ovule** **Pollen Formation** ** Each anther has four pollen sacs** ** Inside pollen sacs, cells undergo meiosis and\ cytoplasmic division to form microspores** ** Microspores undergo mitosis to form pollen grains\ ** **Events inside the Ovule** ** Cells are forming on the inner wall of the flower\'s ovary -\> each is the start of ovule** ** Each cell mass grows, a tissue form within it\ and protective layers (integuments) form around it** ** Meiosis of a cell in ovule produces 4 haploid spores\-- megaspores** ** All megaspores but one disintegrate** ** It undergoes mitosis three times without\ cytoplasmic division** ** Result is a cell with eight nuclei** ** Division produces seven celled female gametophyte** ** One cell is egg, another will form endosperm** **The embryo sac typically contains eight nuclei in seven cells** ** There are six of these cells, including the egg; each contains one nucleus** ** The central cell contains two polar nuclei\ ** **What is the difference between pollination and fertilization?** **Pollination and Fertilization** **Pollination** ** transfer of pollen grains to a receptive stigma** ** pollen can be transferred by a variety of agent** ** when a pollen grain lands on the stigma it germinates\ ** **Fertilization** ** after pollination** ** fusion of gametes** **Double Fertilization in Plants** ** Pollen is deposited on the stigma** ** A pollen tube grows down through the ovary tissue** ** It carries two sperm nuclei** ** When pollen tube reaches an\ ovule, it penetrates embryo sac and deposits two sperm** ** One fertilizes the egg, other fuses with both nuclei of endosperm mother cell\ ** **Endosperm Formation** ** Occurs only in angiosperms** ** Fusion of a sperm nucleus with the two nuclei of the endosperm mother cell produces a triploid (3n) cell** ** This cell will give rise to the endosperm, the nutritive tissue of the seed** **Why are some flowers sweet smelling?** ** Some epidermal cells of petals produce fragrant oils.** **\ What gives the petals their shimmer and color?** ** Cells of tissue contain pigments such as carotenoids and anthocyanins, plus small, light-refracing crystals.** **\ What does a flower\'s fragrance or its coloration, patterning or arrangement of petals do?** ** Attract pollinators.** **\ Pollinating Agents 1** **INSECTS** ** Butterflies** - **flowers red or orange components\ ** - **fragrant/scented\ ** - **distinctive patterns/shapes** - **Bees** ** scented** ** flowers yellow, blue or purple** ** see ultraviolet-light- absorbing\ ** **Flies and beetles\ ** ** flowers that smell like rotten meat, moist dung, or decaying litter on the forest floor** **Ultraviolet Markings on** **nectar guides=\"Nectar here!\"** **Pollinating Agents 2\ BIRDS** ** flowers yellow, orange, or red** ** no strong scent** ** plants don\'t divert metabolic resources to making fragrances** **\ Pollinating Agents 3** **BATS** ** flowers with dusky white petals** ** scented** **Pollinating Agents 4\ WIND** ** flowers make large amounts of pollen** ** have smaller petals or no petals** ** no scent or nectar** **Inflorescence and Pollination\ ** ** Inflorescence is the arrangement of flowers on the floral axis.** ** The flowers are arranged with respect to a fixed floral axis.\ ** **Types of Inflorescence** **Racemose (Indefinite)** **Cymose (Definite)** **Inflorescence and Pollination** **Inflorescences serve as a way for a plant to maximize its reproductive success.** ** Flowers are collected into showy structures to better attract pollinators, to increase seed production, or aid in seed dispersal.** **Inflorescences can result in platforms suitable for insects or birds to land upon.** ** Some inflorescences are tough and protect the floral parts from damage from the elements or from pollinating mammals.** ** What is coevolution?** ** What are examples of ways that plants and their animal pollinators have affected one another\'s evolution?** **Coevolution** ** Reciprocal adaptation** ** 2 species (flowering plant, animal pollinator) form interdependent relationship affecting one another\'s evolution** ** A heritable change in one species affects selection pressure operating between them , so the other species evolved, too** ** Example:** ** flowers with large, showy petals and scent** ** bees with hairy bodies that catch pollen grains** **Coevolution of a flower and an insect pollinator** **The long floral tube of the Madagascar orchid Angraecum sesquipedale has coevolved with the 28-cm-long proboscis of its pollinator, the hawkmoth Xanthopan morganii praedicta. The moth is named in honor of Darwin\'s prediction of its existence** **SUMMARY** **1. Asexual reproduction results in new individuals genetically identical to the parent. The parent and all progeny are equally adapted to the habitat.** **2. Sexual reproduction results in progeny that differ from each other genetically. There is a range of fitness, and some progeny may have a combination of maternal and paternal genes that causes them to be even better adapted than the parents.** **3. All seed plants have a life cycle that consists of an alternation of heteromorphic generations. Microgametes and megagametes are produced by microgametophytes and megagametophytes that grow from microspores and megaspores. Most species have only one type of sporophyte, capable of producing both types of spores. Dioecious species have two types of sporophytes, one of which produces microspores and the other megaspores.** **4. Flowers contain all or some of the following: nonessential organs---pedicel (pedicel is a stem that attaches a single flower to the inflorescence,** **supports an individual flower or fruit, transports nutrients and water, and provides the correct orientation of the flower to attract pollinators and facilitate pollination), receptacle (The part of a flower stalk where the parts of the flower are attached, The receptacle is the thickened top portion of the pedicel that connects to the flower\'s base. This part supports the flower and holds the floral whorls.), sepals, and petals; and essential organs---stamens and carpels.** **5. In flowering plants, [the microgametophyte consists initially of a vegetative cell and a generative cell, but the latter divides into two sperm cells. The megagametophyte consists of the egg cell, two synergid cells, a binucleate central cell, and three antipodal cells.]** **6. After fertilization, the zygote (fertilized egg) grows into an embryo; polar nuclei fuse with the second sperm nucleus, establishing the endosperm nucleus and endosperm, and the integuments develop into a seed coat. The entire structure is a seed. The ovary develops into a fruit.** **7. Inflorescences are groups of many flowers. They may be determinate or indeterminate and may contain several types of specialized flowers.** **8. Fruits protect seeds during development and may aid in their dispersal and maturation. Fruits are either dry, inedible, dehiscent, or indehiscent, or they are fleshy, edible, and indehiscent.** **IMPORTANT TERMS** **alternation of generations** **anther** **carpels** **coevolution** **compatibility barriers** **complete flowers** **cotyledons** **cross-pollination** **double fertilization** **embryo sac** **endosperm** **epicotyl** **fruit** **gametes** **gametophyte** **heteromorphic generations** **hypocotyl** **imperfect flowers** **incomplete flowers** **inflorescence** **karyogamy** **ovary** **ovules** **pedicel** **perfect flower** **petals** **plasmogamy** **pollen** **pollen tube** **radicle** **receptacle** **seed coat** **seeds** **sepals** **spores** **sporophytes** **stamens** **stigma** **style** **syngamy** **zygote** **REVIEW QUESTIONS** **1. Reproduction can serve two very different functions. What are they?** **2. Under what conditions is it selectively advantageous for a plant to produce offspring identical to itself?** **3. Imagine a plant that has been well adapted to a particular habitat, and it has been reproducing only asexually; thus, all of its offspring are identical to it. If the climate or other conditions change such that the plant can no longer survive in the new conditions, what will happen to all of its offspring? Why?** **4. With asexual reproduction, are progeny ever more fit, more adapted than the parent?** **5. Sexual reproduction produces offspring that are not identical to each other or** **to either parent. Usually, some are more well adapted than the parents. Some** **are more poorly adapted, and most are about as adapted. What is one of the** **beneficial aspects of this diversity?** **6. In stable populations, ones that are neither increasing nor decreasing in abundance (e.g., there are a million trees now and there will be a million trees a thousand years from now), about how many of a plants seeds survive and grow to adulthood, being able to replace it when it dies? If during the plant's lifetime it produces 100,000 seeds, how many do not survive, do not grow, and cannot replace it when it dies. (Hint: Do not think of humans, as we are an increasing population, not a stable one. Almost all our children survive, but that is not true of any other species.)** **8. Describe the life cycle of us humans. Are the tissues and organs in our bodies made up of diploid cells or haploid ones? Our reproductive organs make sperm cells in males and egg cells in females. Is this done by mitosis or meiosis? When our bodies make gametes, does every cell in our body become a sperm cell or an egg cell, or do just some of the cells in our reproductive organs do this? Can our haploid sperm and egg cells undergo mitosis and grow into new animals that look like us but are haploid instead? (Haploid eggs do grow in bees. They develop into males.) After a fertilized egg (a zygote) is formed, is it diploid or haploid? Can it immediately undergo meiosis to make four new sperm cells or egg cells, or can it only grow by mitosis into another person?** **9. The plants we are familiar with are called sporophytes or the sporophyte generation. Do these plants have bodies made up of diploid cells or haploid ones? In which organs does meiosis occur (two are correct)---leaves, stems, stamens, roots, carpels, or petals? When plants undergo meiosis, do all cells of the plant undergo meiosis? Do all cells become haploid, or does meiosis occur in just a few cells in some flower parts?** **10. In animals, meiosis produces gametes (sperm cells and egg cells), but that does not happen in plants. When some of the cells of a sporophyte undergo meiosis, what types of cells are produced? What do they grow into?** **11. What is a gametophyte? How many different types of gametophytes are there in a plant life cycle? What do they look like (Hint: See Figure 9-5b)? Do the sporophytes and gametophytes of seed plants ever look like each other?** **12. Draw and label a microgametophyte of a flowering plant. What type of gamete does it produce? Draw and label a megagametophyte of a flowering plant. What type of gamete does it produce?** **13. Flowers typically have many parts, although some flowers can be missing some of the standard parts. What is the name of each of the following parts:** **a. The stalk of the flower** **b. The end of the stalk, where the other parts are attached** **c. The parts that are usually green and protect the flower bud as it develops** **d. The parts that attract pollinators** **e. The parts that produce pollen** **f. The parts that receive pollen and which contain ovules** **14. If a flower has all of the parts c, d, e, and f in Question 13, they are said to be \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ flowers. If they are missing any of these parts, they are said to be \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ flowers. Parts e and f are especially important because they produce the reproductive cells, the spores. If a flower has both e and f in Question 13, they are \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ flowers. If they are missing either e or f or both, they are \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ flowers.** **15. In flowers that are pollinated by wind or water, which of the parts in Question 13 is often missing?** **16. What is the difference between a perfect and an imperfect flower? What is the difference between a complete and an incomplete flower?** **17. A stamen usually has two parts. The stalk is called a \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ and an upper portion, the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, which produces the pollen. Only some of the cells in the upper part undergo meiosis and become pollen grains (microspores). Those cells are called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ mother cells or \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. Neighboring anther cells, in a layer called the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, act as nurse cells.** **18. Carpels usually have three parts: a \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ that catches pollen grains, a \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ that elevates the first part, and an \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ where megaspores are produced. In this last part, there are placentae that bear small structures called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ each with a short stalk called a funiculus and a central mass of parenchyma called the nucellus. One cell in the nucellus will be the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ mother cell or \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.** **19. The megaspore in most flowering plants grows into a megagametophyte that has seven cells and eight nuclei. Name and describe the seven cells.** **20. After pollen lands on a stigma, it is far away from the ovule with the megagametophyte, which holds the egg (the megagamete). How are the two sperm cells transported from the stigma to the egg?** **21. In angiosperms, as a sperm cell enters the egg, it loses both \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ such that only the sperm cell nucleus contributes any DNA to the new zygote. In gymnosperms, however, the sperm cell loses only its \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ such that the zygote inherits both plastids and a nucleus from the sperm cell.** **22. After the sperm cells enter a synergid, one fertilizes the egg in a two-step process. First there is fusion of the sperm cell's protoplasm with that of the egg, a step called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. Then the sperm cell nucleus fuses with the egg cell nucleus, the second step, called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.** **23. What happens to the second sperm nucleus, the one that does not fertilize the egg cell? What is the tissue that develops from this second "fertilization"? How is coconut related to this?** **24. In most eudicot seeds, the parts of the embryo are very easy to see. Describe each of these parts:** **a. Cotyledons** **b. Radicle** **c. Hypocotyl** **d. Epicotyl** **e. Extra credit portion: Answer the following question if you have read about the radicle with regard to a taproot system and a fibrous root system: How is the radicle involved in these different types of root** **systems?** **25. What are albuminous and exalbuminous seeds? Consider corn, peas, and beans. Which of these seeds are which?** **26. After pollination and fertilization, as the ovule develops into a seed, the ovary matures into a \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. Many of these have three parts.** **The \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ is the skin or peel. The** **\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ is the flesh, and the innermost layer, the** **\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, may be tough like the pit of a cherry.** **27. What is the difference between self-pollination and cross-pollination? If pollen is transferred from the stamens of a flower to the stigma of the very same flower, is that cross-pollination or self-pollination? If it is transferred from the stamen of one flower to the stigma of another flower on the very same plant? If it is transferred from the stamen of one flower to the stigma of another flower on a different plant, but a plant that is a clone of the first one? Animals do not have pollen, of course, but why is it that most animals never have to worry about the equivalent problem of self-fertilization? Why cannot most animals fertilize themselves?** **28. Describe a species that is dioecious. Name several examples (Hint: See Figure 9-6). In order for sexual reproduction to occur in a dioecious species, how many separate plants must be involved? Name them all.** **29. Describe a monoecious species. Name several examples.** **30. In several pairs of plant and animal species, plants have become modified such that only its animal partner can pollinate it, and the animals have become modified such that they are especially well adapted to pollinate just their plant partner. What is the name of this type of evolution that results in two organisms becoming particularly adapted to and dependent on each other?** **31. Explain the following terms: inferior ovary, superior ovary, actinomorphic flower, zygomorphic flower. How is each of these modifications selectively advantageous?** **32. What is an inflorescence? The inflorescences of a sausage tree (Figure 9-29) hang far down out of the tree. How is this of benefit to bats? Why can the inflorescence of *Combretum* (Figure 9-30B) attract more pollinators than can the individual flowers?** **33. After pollination and then fertilization, what usually happens to each of the following: stigma, style, carpel, ovule, integuments, and zygote?** **34. Fruits are often classified as dry or fleshy. What is the difference? Which of these two are dehiscent, which are indehiscent?** **35. In ordinary English, we use the word fruit to mean something sweet and juicy; however, the following things are fruits: peanut shells, pea pods, bell peppers, and chili peppers. What is the characteristic that lets us know these really are fruits even though they are not sweet? In contrast, bananas are fruits that do not have this characteristic (they are sterile and new plants must be grown from buds that sprout near the base of the plant).** **36. Some things that we call fruits are not true fruits but instead are accessory (false) fruits. What is the red part of a strawberry, and what are the true strawberry fruits (Hint: See Figure 9-32A)? In an apple, what is the fleshy part that we eat, and what is the core that we throw away?**