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Reproduction 101110032348-phpapp02
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Transcript of Reproduction 101110032348-phpapp02
- 1. Reproduction in some forms of life
- 2. Reproduction
Forms the next generation of species
The means to continue life (perpetuation of species)
May be sexual or asexual - 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 organisms - 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. Paramecium
- 6. Examples of Asexual reproduction
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 - 7. Budding in Hydra
- 8. Examples of Asexual reproduction
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 hasaportion of the central disk, each piece grows the rest of the central disk and the for other arms - 9. Sea stars
- 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. 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.
- 13. Asexual or Vegetative Reproduction in Flowering
Plants
- 14. 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 - 15. 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 (from the stock and scion) - 16. 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 - 17. Pistil/Carpel female reproductive part
Stigma sticky topmost part
Style slender stalk that supports the stigma
Ovary swollen base
Ovules found inside the ovary - 18.
- 19. Stages of Sexual Reproduction in Plants
Formation of Gametes
Megasporogenesis formation of female gametophyte
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 - 20. b. Pollination transfer of the pollen grain from the anther
to a stigma of a flower
Self-pollination pollen is transferred from the anther to the stigma of the same flower
Cross-pollination pollen is transferred from the anther to the stigma of another plant - 21. 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)
Embryo + endosperm + covering layers of the ovule seed - 22. d. Fruit and seed development
ovary fruit
ovule seed
Seed embryo, stored food and seed coat/testa
Embryo cotyledon, hypocotyl and epicotyl - 23. 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