Developmental Biology

• Developmental Biology includes embryonic development, postnatal processes like growth, metamorphosis, regeneration, and tissue repair
• Vertebrates are animals with a spinal column, including mammals, birds, reptiles, amphibians, and fishes
• Embryology is the branch of biology dealing with embryos and their development, starting with fertilization and ending with metamorphosis
• Metamorphosis is a major developmental change as an animal or insect becomes an adult from fertilization to birth
• Special fields in embryology include Descriptive Embryology, Comparative Embryology, Experimental Embryology, Chemical Embryology, Teratology, and Reproductive Biology
• In vitro fertilization (IVF) involves combining a woman's egg cells with a man's sperm cells outside the uterus, then implanting the fertilized egg in the woman's uterus to begin the pregnancy cycle
• Embryology in contemporary society includes techniques like examination of amniotic fluid, ultrasound, x-ray imaging, and determining sex before birth
• Vertebrate embryology studies the development of vertebrates from fertilization to metamorphosis in Amphibia, hatching in birds, and birth in mammals
• The Theory of Epigenesis refuted the preformation theory by proposing that neither eggs nor sperm had the structure like 'humunculus' but contained substances capable of forming the organized body after fertilization
• Karl Ernst von Baer's Law emphasizes that the more general basic features of any animal group appear earlier in development than the special features peculiar to different members of the group
• The development of cell theory involved Matthias Schleiden concluding all plant parts are made of cells, Theodor Schwann stating all animal tissues are composed of cells, and August Weismann distinguishing soma (body) and germ-cell line (gametes)