LIFE CYCLE AND REPRODUCTIVE STRUCTURES
Download as PPTX, PDF4 likes2,730 views
The document provides a detailed overview of plant reproduction, covering both asexual and sexual reproduction processes, along with meiosis and alternation of generations. It explains reproductive structures such as cones and flowers, their parts and functions, and outlines seed and fruit structures along with their roles in reproduction. Key concepts include vegetative propagation, gamete formation, and the complexities of plant life cycles.
LIFE CYCLE AND REPRODUCTIVE STRUCTURES
- 1. BSc. Bio, MPCHS ᴓ1 CHAPTER 6 Tel – (+231) 880-897-558 / 770-405-161 Email - fkollie25@gmail.com
- 2. 1. Overview of Plant Reproduction 2. Meiosis and Alternation of Generations 3. Cone and Flower Structure 4. Seed Structure 5. Fruit Structure
- 3. 1. How plants produce offspring of their kind 2. Distinguish between cones and seeds 3. Have an idea of the structure of a seed and its role in reproduction in plants 4. Distinguish between meiosis and mitosis 5. Identify the parts of a fruit and its role in plants
- 5. OVERVIEW OF PLANT REPRODUCTION • Reproduction is the capacity of all living things to give rise to new living things • This includes the transmission of hereditary material from parent/parents to offspring • Reproduction can be describe in terms of life cycles • Life cycle of a species is a sequence of stages leading from the adults of one generation to the adults of the next generation • Life cycle can be either; – Asexual – Sexual
- 6. ASEXUAL REPRODUCTION • Also known as “Vegetative reproduction” • A process in which new organism is produced from a single parent without the involvement of gametes or sex cells • Offspring are genetically identical to the parent • Such offspring are often referred to as clones • The primary form of reproduction for single- celled organisms such as archaea, bacteria, and protists.
- 7. • Asexual reproduction involves cell division by mitosis • Many plants and fungi reproduce mostly asexually • Asexual reproduction is more reliable than sexual reproduction • Plants have two main types of asexual reproduction: – Vegetative reproduction – Sporulation ASEXUAL REPRODUCTION
- 8. Vegetative Reproduction • Also called “Vegetative propagation” • Most plants have roots, stems and leaves. These are called the vegetative parts of a plant • A type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds. • Bryophyllum (sprout leaf plant) has buds in the margins of leaves • If a leaf of this plant fall on a moist soil, each bud can give rise to a new plant
- 9. • Plants produced by vegetative propagation take less time to grow and bear flowers and fruits earlier than those produced from seeds • The roots of some plants can also give rise to new plants. Sweet potato and dahlia are examples. • There are two types of vegetative reproduction; –Natural vegetative propagation –Artificial vegetative propagation Vegetative Reproduction
- 10. • Spore is a reproductive cell of plants that can develop into an adult without fusing with another reproductive cell. • Organisms use spores as a means of asexual reproduction • Spores are usually haploid and unicellular and are produced by meiosis in the sporophyte. • Spores are found in seedless vascular plants such as; mosses and ferns • Bacteria, fungi, algae and some multicellular organism do contain spore Sporulation
- 11. • Sexual reproduction involves two parents • Offspring form are genetically different from both parents and from one another • Sexual reproduction results in new genetic combinations • Offspring produce are genetically variable • This form of reproduction is essential for plants that grow in a variety of different environments SEXUAL REPRODUCTION
- 12. • Three types of reproductive cells are involve in reproduction in plants; – Spores, Sperms and Eggs • Sperm and egg are referred to as gametes • Sexual reproduction involves some risk because egg cells or sperm cells can be damaged or destroyed, thus, hindering reproduction. SEXUAL REPRODUCTION
- 13. • Multicellular organism at some point during their sexual life cycles return to two single cells; sperm and egg. • These cells combine to become a zygote that develops into a new multicellular organism • Meiosis is a type of nuclear division that is involved only in sexual reproduction and results in daughter cells with half the original number of chromosomes. • Daughter nuclei produced by meiosis have one copy of each chromosome MEIOSIS & ALTERNATION OF GENERATION
- 14. • Two types of nuclear division occurs in plants; –Mitosis and Meiosis • Both nuclear divisions have different effects on the number of chromosomes in the daughter cells. • Mitosis produce two daughter nuclei with the same number of chromosomes • Meiosis produce four daughter nuclei, each with half the number of chromosomes as the original nucleus. • Chromosomes number in a cell vary from species to species MEIOSIS
- 16. • Somatic cell in plants typically contains either one set of chromosomes or two sets of chromosomes • In cell with two sets of chromosomes, each pair of chromosomes is called a pair of Homologous chromosomes • A cell with two set of chromosomes is said to be diploid • Haploid has a single set of chromosomes • In the Evening primrose (Oenothera lamarckiama), diploid number (2n) is 14 whereas haploid (n) is 7 MEIOSIS
- 19. • In plants mitosis can occur in haploid, diploid or polyploid cells • Meiosis can only occur within a diploid or polyploid cell with even number of chromosomes • Meiosis involves two-step division process.; – Meiosis I – Meiosis II • Homologous chromosomes separate during meiosis I • Sister chromatids separate during meiosis II • The stages of meiosis are; Prophase, Metaphase, Anaphase, Telophase and Cytokinesis MEIOSIS
- 20. MEIOSIS I
- 21. MEIOSIS II
- 22. • Plant sexual life cycles are more complex because two multicellular forms of each plant exist. • One form is called the sporophyte (spore-producing plants) • Consist of diploid cells (2n) • The other form is gametophyte (gamete producing plant) • Consist of haploid cells (n) • Plant life cycle involves alternation of generation ALTERNATION OF GENERATION
- 24. • A typical sexual life cycle of a plant involves five (5) steps; ❶ Cells of multicellular diploid sporophyte undergo meiosis to produce haploid spore ❷ The spores undergoes mitosis to produce multicellular, haploid gametophyte ❸ One or more cells of the gametophyte undergo mitosis to produce haploid sperm or egg ❹ Sperm and egg combine in fertilization to produce a diploid zygote ❺ The zygote undergoes mitosis to produce a multicellular, diploid sporophyte ALTERNATION OF GENERATION
- 26. ALTERNATION OF GENERATION CHART
- 27. • In plants, meiosis produce only haploid spores whereas in animals it produces only gametes • Plant species vary in the relative sizes of sporophytes and gametophytes and in whether each form can live independently or not • In most bryophytes, the gametophyte is larger than the sporophyte • In vascular plant, the gametophyte is much smaller than the sporophyte ALTERNATION OF GENERATION
- 28. • Cones and flowers of seed plants facilitate sexual reproduction • Cones and flowers form after apical meristems develop into reproductive meristems • Both structures have Sporophylls, which are modified spore-producing leaves • Sporopylls contain sporangia, hollow structures that produce spores and spores then give rise to gametophytes • Pollination precede after gametes formation in seed plants • This is later followed by fertilization CONE AND FLOWER STRUCTURE
- 30. CONE PRODUCTION IN GYMNOSPERMS • Gymnosperms are known for their characteristic cones that bear exposed seeds • Apical meristems becomes reproductive structures • They develop into either Pollen cones or Ovulate cones • Pollen cone of pine trees form from meristem that produce a stem with attached leaves • The stem becomes the cone axis, whereas the leaves are modified into papery sporophylls containing sporangia
- 31. Sporophyll
- 33. • Angiosperms are known for their characteristic flowers that bear enclosed seeds. • Apical meristem become reproductive structures • They develop into Male, Female, or Bisexual flowers • Pollinators facilitate the process of reproduction in flowering plants by transferring pollen grains from males to female parts of flowers • Pollinators are attracted to the flowers by colors, nectar, and other attractants. FLOWERS PRODUCTION IN ANGIOSPERMS
- 34. Bisexual flowers
- 35. COMPONENT OF A TYPICAL FLOWER FLOWER • Reproductive organ of angiosperms • Angiosperms – flowering plants • Modified shoot with four whorls • SEPAL – calyx • PETALS – corolla • STAMENS – androecium • PISTILS - gynoecium Non-reproductive parts Reproductive parts
- 36. FLOWER PART FORM AND FUNCTION Peduncle The stalk of a flower Receptacle Part of flower stalk bearing the floral organs at the base of the flower Sepal Leaf-like structures at flower base that protect young flower bud. Often green and leaf-like Calyx All the sepals together form the calyx Petal Located in and above the sepal, often large and colorful, sometimes scented, sometimes producing nectar. Often serve to attract pollinators to the plant Corolla All the petals together form the corolla Stamen Male part of the flower, consisting of the anther and filament, makes pollen grains (male gametes)
- 39. FLOWER PART FORM AND FUNCTION Anther The pollen bearing portion of a stamen Filament Stalk that connect the anther to the base of the flower Pollen Grains containing the male gametes. Immature male gametophyte with a protective outer covering. Carpel/Pistil Female part of the flower. Consisting of the stigma, style and ovary Stigma Often sticky top of carpel, serves as a receptive surface for pollen Style The stalk of a carpel, between the stigma and the ovary, through which the pollen tube grows Ovary Enlarged base of the carpel containing the ovule or ovules. The ovary matures to become a fruit Ovule Located in the ovaries. Carries female gametes. Ovules become seeds on fertilization.
- 40. Flowers can vary in the type of structure present, absent or present of both fertile types of modified leaves and in their symmetry • A flower containing all four modified leaves is said to be Complete • A flower that lacks one or more of these modified leaves is said to be Incomplete TYPES OF FLOWER
- 41. UNISEXUAL FLOWERBISEXUAL FLOWER TYPES OF FLOWER
- 42. SYMMETRY OF A FLOWER Regular or actinomorphic flower (Radial symmetry) Irregular or zygomorphic flower (Bilateral symmetry) Radially symmetric; divisible into two essentially equal portions along any median longitudinal plane Bilaterally symmetric; divisible into two equal portion along only one median longitudinal plane
- 43. OVARY POSITION IN FLOWERS
- 44. • Seeds facilitate plants’ survival through hard times • Seed: ripened ovule containing embryo • It is developed in the embryo sac of the ovule in ovary of a flower • Seed formation completes the process of reproduction in seed plants • Gymnosperms and angiosperms produce seeds SEED STRUCTURE
- 45. • In gymnosperms, seeds are produce on or near bracts • Bracts are exposed leaves found on cones • Angiosperms produce seeds inside the ovaries of flowers • Ovule forms as an attachment to a modified leaf and develops into a seed after fertilization • The integument harden to become the seed coat SEED STRUCTURE Apple seed inside ovary Bract
- 46. • Maintain dormancy until better environmental conditions arise • Protect developing embryos • Provide nourishment until photosynthesis is possible • Aid in dispersal of plants SEED FUNCTIONS
- 47. • External – Seed coat (testa) – Hilum • Embryo – Cotyledon – Epicotyl – Plumule – Radicle SEED STRUCTURE
- 48. 1. Seed absorbs water under the right atmospheric condition 2. Water cracks the seed coat, activating growth 3. Root shoot (hypocotyl) begins to grow downward 4. Stem shoot (epicotyl) begins to grow upward 5. Normal growth continues… – Green leaves begin to develop STEPS IN GERMINATION PROCESS
- 49. SEED GERMINATION IN DICOTS
- 51. • fruit is a reproductive structure of an angiosperm which develops from the ovary and accessory tissue, which surrounds and protects the seed • In flowering plants, seed are enclosed in an ovary • Ovary expand to produce a fruit after fertilization and seed development FRUIT STRUCTURE
- 52. • Fruit protect the developing embryo from drying out • Protect the embryo from diseases and herbivores • Promote seed distribution by animal that eat the fruit • Provide ready-made fertilizer for the germinating seed FRUIT FUNCTION
- 53. • A typical fruit consists of a mature ovary with enclosed seed • Fruits primary function is to distribute seeds to new areas where the plants might grow • Fruits can be either fleshy or dry • The wall of the ovary called the pericarp, consists of three parts; – Exocarp – Mesocarp – Endocarp
- 54. • Generally, there are three (3) types of fruits; • Simple fruits, Aggregate fruits and Multiple fruits • These are classified according to the arrangement from which they derive • Simple fruits develop from a single flower with a single ovary (pistil) • Aggregate fruits develops from one flower that has many separate ovary (pistil) • Multiple fruits develops from the pistils of more than one flower TYPES OF FRUITS
- 56. ❶ Simple fleshy fruits ❷ Simple Dry fruits Dehiscent Dry Indehiscent Dry Fruits develop from a single ripened ovary (pistil) of a single flower
- 57. ❶ Simple fleshy fruits • In simple fruits that are fleshy, one or more layers of the pericarp become soft during ripening • Pericarp fleshy at maturity • The basic types includes: Berries Hesperidia Pepos Drupes Pomes
- 58. BERRIES • Fruits having one to many seeds and a pericarp that becomes soft and often sweet and slimy as it matures • Eg: Grapes, dates, eggplant, tomatoes, green peppers, blueberries, guavas, banana etc HESPERIDIA • Fruits similar to berries but with a leathery pericarp that produces fragrant oils • Eg: All citrus fruits such as oranges, lemons, lime, grapefruit
- 59. POMES • Bulk of the fruit is formed from a swollen receptacle • Eg; Pears, apples
- 60. Simple Fruits - Dehiscent Dry • Dehiscent dry fruits are fruits that open at maturity to shed seeds. • The basic types includes; Follicles Legumes Siliques Capsules ❷ Simple Dry fruits
- 61. FOLLICLES • Fruits that open along one seam when the seeds are to be released • Eg: Milkweed, columbines, peonies, mangnolia LEGUMES • Fruits split into two seed-bearing halves. Seeds can be born in a common ovary or in separate compartments • Eg: Garden peas, beans, mesquite, peanuts
- 62. SILIQUES • Dry fruits in which the seeds reside on a partition between halves of the ovary • Eg: shephers’s purse, cabbage, watercress, radish CAPSULES • Fruits of to or more carpels, split along seams or forming caps or pores • Eg: popples, irises, snapdragons, orchids, yucca
- 63. Simple Fruits - Indehiscent Dry • Indehiscent dry fruits are fruits that remain closed at maturity • The basic types includes; Nuts Schizocarps Achenes Samaras Caryopses or grains
- 64. NUTS • Dry fruits with hard, thick pericarp and a basal cup • Eg: acorns, hickory nuts, chestnuts, hazelnuts SCHIZOCARPS • Have a hard, thin pericarp that splits into two halves. • Eg: carrots
- 65. ACHENES • Have thin pericarps. The single seeds connect to the pericarp only at their base • Eg: sunflowers, buttercups SAMARAS • Have thin pericarps. The seeds occur in pairs and have wings that allow dispersal by the wind • Eg: maple, elm, ash
- 66. CARYOPSES • Grass seed in which the fruit has a hard pericarp, which is fastened to the embryo all the way around • Eg: All members of the grass family, such as corn and rice
- 67. • Aggregate fruits develops from one flower that has many separate ovary (carpels) • Eg: Blackberries, strawberries, raspberries, magnolias
- 68. • Multiple fruits develops from the pistils of more than one flower • Eg: pineapples, mulberries, figs, breadfruit