DEVBIOLEC L1: Nature and Scope of Developmental Biology

• Embryology is the study of embryo.
• Embryo is the juvenile stage of an animal contained in the egg or in maternal body.
• Oviparous organisms lay egg where the nutrients are in the yolk that hatch when it is depleted.
• Oviparous organisms have independent development from their mother.
• Viviparous organisms give birth and nutrients are transmitted through an umbilical cord.
• Viviparous organisms have dependent development from their mother.
• Ovoviviparous organisms are hybrid; eggs are retained inside the mother.
• Ovoviviparous organisms have independent development from their mother.
• Developmental Biology is the study of embryonic and other developmental processes.
• Development is the slow process of progressive changes of organisms that may be morphological or physiological.
• The two kinds of development are Ontogeny and Phylogeny.
• Ontogeny is the development of the individual.
• Phylogeny is the historical development of the species, evolutionary history.
• Phases of Ontogenic Development

  1. Gametogenesis
  2. Fertilization
  3. Cleavage
  4. Gastrulation
  5. Organogenesis
  6. Growth
  7. Differentiation
  8. Morphological Differentiation
  9. Physiological Differentiation
  10. Chemical Differentiation
  11. Morphogenesis
  12. Birth / Hatching
  13. Maturation
• Gametogenesis is the gamete formation.
• Fertilization is the fusion of gametes.
• Cleavage is the mitotic division of the fertilized egg.
• Gastrulation is the movement and rearrangement of cells establishing three germ layers: ectoderm, mesoderm, and endoderm.
• Organogenesis is the organ formation where germ layer split up into smaller group of cells called primary region rudiments.
• Examples of organogenesis are neurogenesis and heart into 2 chambers.
• Growth is the increase in size or mass.
• Thalidomide is a teratogen that causes phocomelia or amelia to babies.
• Differentiation is the events by which parts become different from each other and also different from what they originally were (zygote and stem cells).
• Morphological Differentiation is where individual cells or group of cells become structurally different from one another.
• Physiological differentiation, although all cells have exhibit common basic attributes, eventually they perform different functions.
• Examples of Physiological differentiation are neuron that receive and transmit impulses, muscles for contraction, and RBC for transport.
• Cytological differentiation and physiological differentiation are product of Chemical Differentiation .
• Chemical differentiation are based on enzymes which direct synthesis of organic compounds that give cell its uniqueness.
• Chemical Differentiation as products of unique enzymatic factors.
• Morphogenesis is the acquisition of body form of an organism.
• Morphogenesis forms the characteristic size and shape and tissue and organs that make up the organism.
• Birth or Hatching is the act or process of bearing or bringing forth the offspring.
• Maturation or maturity is the independent growth and development of the offspring.
• Branches of Developmental Biology:

  1. Descriptive Embryology
  2. Comparative Embryology
  3. Experimental Embryology
  4. Chemical Embryology
  5. Teratology
  6. Reproductive Biology
• Descriptive Embryology is the direct observation and description of embryological development.
• Comparative Embryology studies similarities and differences in the development of animals
• Experimental Embryology examine cellular control and development.
• Chemical Embryology studies developmental stages studied by biochemical and physiological techniques.
• Teratology is concerned with the study of malformations.
• Reproductive Biology focuses on problems with conception and contraception.