Biology 1

• Propagation of flowering plants

  • Sexual reproduction
  • Asexual reproduction
• Life cycles of plants


  • Alternation of generations
  • Haploid (n) and diploid (2n) generations taking turns producing each other
• Sporophyte (diploid plant)


  1. Produces haploid spores by meiosis

  2. Spores divide by mitosis and give rise to gametophytes (small male and female haploid plants that produce gametes: sperm and eggs)

  3. Fertilization results in diploid zygotes

  4. Zygotes divide by mitosis and form new sporophytes
• Flower


  Reproductive shoots of the angiosperm sporophyte
• Floral organs


  • Sepals
  • Petals
  • Stamens
  • Carpels (pistils)

  
• Sepals


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


  More brightly colored than sepals and attract the flower to insects and other pollinators
• Stamen


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


  Has an ovary, a style, and a stigma
• Types of flowers based on presence of whorls

  • Complete
  • Incomplete
• Types of flowers based on presence of reproductive whorls


  • Perfect/Bisexual
  • Imperfect/Unisexual
• Gametophyte development and pollination

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

  2. Pollen grains (mature male gametophyte) formed in pollen sacs

  3. Egg-producing female gametophyte (embryo sac) forms within each ovule

  4. Pollination is transfer of pollen from anther to stigma

  5. Pollen tube grows and discharges sperm, resulting in fertilization of egg

  6. Zygote gives rise to embryo, ovule develops into seed

  7. Ovary develops into fruit containing one or more seeds
• Double fertilization


  Pollen grain germinates and produces pollen tube that extends to ovary
• From ovule to seed

  Ovule develops into seed, embryo develops from zygote and stores proteins, oils, and starch
• From ovary to fruit

  Ovary develops into fruit that protects and aids in dispersal of seeds
• Developmental origin of fruits
• Modes of animal reproduction

  • Asexual
  • Sexual
• Asexual reproduction


  Creation of new individuals whose genes all come from one parent without fusion of egg and sperm
• Advantages of asexual reproduction

  • Enables animals living in isolation to produce offspring without mates
  • Creates numerous offspring in short time, ideal for colonizing habitats
  • Perpetuates successful genotypes in stable, favorable environments
• Sexual reproduction


  Creation of offspring by fusion of haploid gametes to form diploid zygote
• Female gamete


  Unfertilized egg (ovum), relatively large and not motile
• Male gamete


  Sperm, generally smaller and motile
• Advantages of sexual reproduction

  • Increases genetic variability among offspring
  • Enhances reproductive success when environment changes rapidly
• Mechanisms of asexual reproduction

  • Fission
  • Budding
  • Fragmentation
  • Regeneration
• Types of fertilization


  • Internal
  • External
• Male reproductive system


  • Male gonad (testis)
  • Sperm duct
  • Penis

  
• Female reproductive system


  • Female gonad (ovary)
  • Oviduct
  • Vagina
• Organisms that use external fertilization


  • Most terrestrial animals
  • Few fish
  • Some aquatic animals
• External fertilization


  Mating partners release eggs and sperms into the water simultaneously
• Organisms that use external fertilization


  • Many fish
  • Amphibians
  • Other sexual aquatic animals
• The details of the reproductive process vary tremendously from one organism to another
• Generalizations were made about animal reproductive systems in order to understand its variations
• Male gonad


  Testis - where sperm are produced

  
• Sperm duct


  Used for the transport of sperm to the exterior of the body
• Penis


  The terminal part of the sperm duct which opens onto or into a copulatory organ
• Female gonad


  Ovary - where eggs are produced
• Oviduct


  A tube for the transport of egg
• Vagina


  The terminal portion of the oviduct responsible for the receiving of male copulatory organ
• Metagenesis


  • An alternation of asexual and sexual generations
  • Example: Hydrozoan Obelia - polyp generation gives rise to medusa generation which reproduces sexually
• Parthenogenesis


  • A form of reproduction in which an unfertilized egg develops into an adult animal
  • Occurs for several generations, then males develop and mate with females