lesson 2 & 3

• Pollination


  The transfer of pollen from an anther to a stigma
• Genetic


  Advantageous makeups
• Identical


  Genetically identical with the parent
• Propagules


  Body parts specialized for breakaway and dispersal
• Scion


  The plant that is to be asexually propagated
• Stock


  The plant that the scion is attached to
• Cambium


  The layer that needs to be in contact for grafting
• Pollen


  Produced by the seed plants, circumvents the requirement for water as a requirement for fertilization
• Fragmentation


  The type of reproduction in which an animal divides into several pieces and then each piece develops into an entire new animal
• Metagenesis


  An alternation of sexual and asexual generations
• Parthenogenesis


  A type of reproduction in which an unfertilized egg develops into a new individual
• Hermaphroditic


  An individual that can produce both eggs and sperm

  
• Gamete


  A sex cell (either egg or sperm)
• Zygote


  A fertilized egg
• The propagation of flowering plants by sexual and asexual reproduction forms the basis of agriculture.
• Plant life cycle


  1. Sporophyte (diploid plant) produces haploid spores by meiosis

  2. Haploid spores divide by mitosis and give rise to gametophytes (small male and female haploid plants that produce gametes)

  3. Fertilization results in diploid zygotes

  4. Diploid zygotes divide by mitosis and form new sporophytes

  
• Flower


  Reproductive shoots of the angiosperm sporophyte, composed of four whorls of highly modified leaves called floral organs
• Floral organs


  Sepals, petals, stamens, and carpels (pistils)

  
• Sepals


  Enclose and protect the floral bud before it opens, usually green and more leaflike
• Petals


  More brightly colored than sepals, attract insects and other pollinators
• Stamen


  Consists of a filament and an anther, where pollen is produced
• Carpel


  Has an ovary at its base, a style, and a stigma that serves as a landing platform for pollen
• Pistil


  A single carpel or a group of fused carpels
• Types of flowers based on the presence of the whorls


  • Complete (has all four parts)
  • Incomplete (missing any of the four parts)

  
• Types of flowers based on the presence of the reproductive whorls


  • Perfect/Bisexual (has both male and female structures)
  • Imperfect/Unisexual (has only male or female structures)

  
• Gametophyte development and pollination

  1. Anthers and ovules bear sporangia where spores are produced by meiosis and gametophytes develop

  2. Pollen grains are formed within pollen sacs of anthers

  3. Egg-producing female gametophyte forms within each ovule

  4. Pollination is the transfer of pollen from an anther to a stigma

  5. Pollen tube grows and discharges sperm near the embryo sac, resulting in fertilization of the egg

  
• Double fertilization


  1. Pollen grain germinates and produces a pollen tube that extends down to the ovary

  2. One sperm fertilizes the egg, forming the zygote

  3. The other sperm fertilizes the central cell, forming the endosperm

  
• From ovule to seed


  1. After double fertilization, each ovule develops into a seed, and the ovary develops into a fruit enclosing the seed(s)

  2. The embryo develops from the zygote and the seed stockpiles nutrients

  
• From ovary to fruit

  1. Fertilization triggers hormonal changes that cause the ovary to begin its transformation into a fruit

  2. The ovary wall becomes the pericarp, the thickened wall of the fruit
• Asexual reproduction


  The creation of new individuals whose genes all come from one parent without the fusion of egg and sperm
• Sexual reproduction


  The creation of offspring by the fusion of haploid gametes to form a zygote (fertilized egg), which is diploid

  
• Egg (ovum)


  The female gamete, a relatively large and non-motile cell
• Sperm


  The male gamete, a much smaller and motile cell
• Advantages of sexual reproduction

  • Increases genetic variability among offspring
  • May enhance reproductive success when environmental factors change rapidly
• Advantages of asexual reproduction

  • Enables animals living in isolation to produce offspring without mates
  • Can create numerous offspring in a short time, ideal for rapid habitat colonization
  • Perpetuates successful genotypes in stable, favorable environments
• Types of asexual reproduction


  • Fission (separation into two or more individuals of equal size)
  • Budding (new individuals arise from outgrowths)
  • Fragmentation (breaking into pieces that develop into new individuals)
  • Regeneration (regrowth of lost body parts)
• Types of fertilization


  • Internal (male delivers sperm directly into female's body)
  • External (gametes are released into the water)

  
• Reproductive systems


  • Male: Testis, sperm duct, penis
  • Female: Ovary, oviduct, uterus, vagina

  
• External fertilization


  Mating partners release eggs and sperm into the water simultaneously
• External fertilization


  • Many fish, amphibians, and other sexual aquatic animals