F. Perpetuation of Life

• Asexual Reproduction in Plants


  • Undifferentiated meristem cells at the growing tips of plants give rise to new plants
  • Resulting new plants are genetically identical to their parents and thus are called clones
• Sexual Reproduction in Plants


  • Offspring are genetically different from the parents
  • Offspring are packaged in a protective seed, which can be long lived and can disperse the offspring some distance from the parents
  • In flowering plants (angiosperms), the seed itself is contained inside a fruit, which may protect developing seeds and aid in their dispersal
• Sporophyte


  The diploid form of plants that consists of roots, shoots, leaves, and reproductive structures such as flowers and fruits
• Gametophytes in Angiosperms

  • Pollen grains (male gametophytes or microgametophytes)
  • Embryo sac (female gametophyte or megagametophyte)
• Double Fertilization

  1. Pollen tube grows toward the embryo sac and releases two sperm cells

  2. One sperm cell fuses with the egg cell to form the diploid zygote

  3. The other sperm cell fuses with the two polar nuclei to form the triploid endosperm nucleus
• Gametes


  Sex cells produced by meiosis, with sperm being the male gamete and ova being the female gamete
• Estrous Cycles


  Reproductive cycles found in most mammals
• Gametogenesis

  1. Spermatogenesis (in males)

  2. Oogenesis (in females)
• External fertilization


  Many gametes are released into the water by each sex at the same time and place. Water is required because animal sperm must swim to the eggs. Water also protects gametes from drying out. Species which have external fertilization are either aquatic or return to water for reproduction (some invertebrates, fishes and amphibians)
• Menstrual cycles


  Reproductive cycles found in humans and some other primates.
• Gene


  A stretch of DNA that contains the instructions for making protein

  
• Genotype


  Genes that are present in the DNA of an organism

  
• Phenotype


  What an organism looks like as a consequence of the genotype and its environment
• Dominant traits


  Traits that are expressed
• The Punnett Square


  A tabular summary of every possible combination of one (1) maternal allele with one (1) paternal allele for each gene being studied in the cross.