ANIMAL BIO LONG Q

• Metamorphosis - a feature in some organisms that involves a rapid change from an immature larvae and juvenile to a sexually mature adult
• Metamorphosis


  Sea stars

  Atlas Moth

  Lady Bugs
• Complete Metamorphosis (holometabolous) - is characterized by distinct larval and pupal stages.
• Holometabolous


  Larva

  Pupa

  Adult
• Incomplete Metamorphosis (hemimetabolous) - is characterized by an aquatic juvenile stage.
• Hemimetabolous


  Naiad

  Adult
• Incomplete Metamorphosis (paurometabolous) - is characterized by a terrestrial juvenile stage.
• Paurometabolous

  Nymph

  Molting Adult
• Fission - involves the splitting of the parent individual into two approximately equal halves.
• Fragmentation - involves breaking body parts into fragments.
• Budding - involves an outgrowth or bud forming in the body of an adult.
• Parthenogenesis - involves the development of an embryo from an unfertilized egg.
• Sexual Reproduction


  Requires Two parents from each of the two sexes

  Requires fusion of the egg cell and the sperm cell
• External Fertilization


  Usually involves the release of gametes into the surroundings.

  Common in aquatic organisms such as fishes and corals.
• Internal Fertilization


  Sperm cells are usually deposited into the female reproductive tract.

  Common among higher animals such as birds, reptiles, and mammals.
• Oviparous - eggs are laid and the embryo obtain its nourishment from the stored yolk nutrients.
• Ovoviviparous - embryos are nourished in egg; which remain in the parents body until they hatch.
• Viviparous - embryos are nourished by the placenta until the mother gives birth to live young.
• Mechanism of Fertilization

  1. Contact with the jelly layered or the zona pellucida.
  2. Digestion by the acrosomal enzymes.
  3. Species specific fusion of gamete membranes (fast-block)
  4. Cortical reaction
  5. Formation of fertilization envelope (slow-block)
• During embryogenesis, the zygote undergoes repeated cell division and cell reorganization.
• Cleavage - refers to the rapid cell divisions that the zygote undergoes.
• Morula - solid ball of cells from continuous division.
• Blastula - hollow ball of cells
• Gastrulation - involves extensive cell migration and rearrangement, which forms the three embryonic germ layers.
• Three Embryonic Germ layers

  Ectoderm

  Mesoderm

  Endoderm
• Embryogenesis - fertilized egg will undergo active cell division and cell differentiation to form embryo.
• organogenesis - where it starts to form several types of tissues.