1. 1. Reproduction in some forms of life
2. 2. Reproduction Forms the next generation of species The means to continue life (perpetuation of species) May be sexual or asexual
3. 3. Asexual reproduction Sexual reproduction Does not involve gametes or sex cells Occurs in many forms and is performed by many lower forms of organsims, including plants No genetic variation in organisms Involves sex cells The sperm and the egg unite to form a zygote Characteristic of many organisms, including plants, animals and humans Increases genetic variation among
4. 4. Examples of Asexual reproduction Fission one cell divides into two either longitudinally, transversely or even diagonally E.g. Algae Volvox and Ulothrix, paramecia, amoeba, bacteria and corals Fragmentation pieces of an organism may break off and develop into whole organisms Colonies of algae, sea anemone, comb jelly, flatworms
5. 5. Paramecium
6. 6. Budding cells in some areas of an organisms body organize themselves to form new individuals or buds Hydra (freshwater polyp) Parthenogenesis (virgin birth) an egg possessing diploid chromosomes develops into an adult without being fertilized Daphnia, rotifers, snails, honeybees and sea urchins Examples of Asexual reproduction
7. 7. Budding in Hydra
8. 8. Paedogenesis smaller larvae develop from bigger larvae and grow up to become adults Flukes, taperworm, ascaris Regeneration demonstrated by sea stars; when a sea star is cut into pieces, such that each arm has aportion of the central disk, each piece grows the rest of the central disk and the for other arms Examples of Asexual reproduction
9. 9. Sea stars
10. 10. Conjugation Sexual reproduction in lower forms of life Genetic material (not necessarily gametes) is transferred between two individuals through a protoplasmic bridge before allowing autotomy (voluntary separation of a body part) to take place Paramecium, bacteria and cyanobacteria, fungi
11. 11. Examples of Asexual reproduction Common bread mold (amag) reproduces through spores encased inside a capsule- like container called sporangium Mosses and ferns spore-producing plants Spores primary structures responsible for asexual reproduction in mosses and ferns
12. 12. Asexual or Vegetative Reproduction in Flowering Plants Vegetative Reproductio n Natural Runners Leaf reproduction Tip layering Artificial Layering Grating and Budding Cutting
13. 13. Natural Vegetative Reproduction Runners grow along the ground from the parent plant; forms adventitious roots and shoots at the tips Strawberry Tip layering allows their aerial stems to arch downwards so that their tips touch the ground Blackberry, raspberry and spider plant Leaf reproduction new plants develop along the margins of their leaves katakataka
14. 14. Artificial Vegetative Reproduction Cutting portions of stems and roots are removed and transferred to loose, damp soil or sand Herbaceous and woody plants such as rose Layering stimulates the growth of roots on a stem; a stem is buried in the ground then cut when roots are formed Grafting and budding splicing together of two stems or the union of their two cambium layers
15. 15. Sexual Reproduction in Flowering Plants: Floral Parts Calyx collection of sepals Corolla collection of petals Stamen male reproductive part Filament slender stalk Anther produces colored grains called pollen, which contains sperm nuclei
16. 16. Pistil/Carpel female reproductive part Stigma sticky topmost part Style slender stalk that supports the stigma Ovary swollen base Ovules found inside the ovary
17. 17. Stages of Sexual Reproduction in Plants a. Formation of Gametes a. Megasporogenesis formation of female gametophyte b. Microsporogenesis formation of male gametophyte Sporogenesis involves a reduction division process that produces haploid gametes: egg in embyo sac and sperm in the pollen grain
18. 18. b. Pollination transfer of the pollen grain from the anther to a stigma of a flower a. Self-pollination pollen is transferred from the anther to the stigma of the same flower b. Cross-pollination pollen is transferred from the anther to the stigma of another plant
19. 19. c. Double-fertilization Pollen grain with two nuclei (generative and tube nucleus) generative nucleus moves into the pollen tube and forms two sperm nuclei tube nucleus grows through the stigma, style and into the ovule, clearing the way for the entry of sperm nuclei 1 sperm nuclei (N) + 1 egg (N) = zygote (2N) 1 sperm nuclei (N) + 2 polar nuclei = endosperm (3N)
20. 20. d. Fruit and seed development ovary fruit ovule seed Seed embryo, stored food and seed coat/testa Embryo cotyledon, hypocotyl and epicotyl
21. 21. e. Seed Germination Viability ability of the seed to germinate Conditions: a. Suitable temperature ( between 16C and 27 C) b. Plenty of moisture c. Sufficient oxygen Seedling young plant that develops out of a plant embryo from a seed radicle root hypocotyl shoot cotyledons seed leaves