4 Fates of the Primary Germ Layers Ectodermhair, nails, epidermis, brain, nervesMesodermnotochord (in chordates), dermis, blood vessels, heart, bones, cartilage, muscleEndoderminternal lining of the gut and respiratory pathways, liver, pancreas
8 Gastrulation in Sea Urchin Embryo Sea urchin gastrulation. DEUTEROSTOMEBegins at the vegetal pole where individual cells enter the blastocoel as mesenchyme cells.The remaining cells flatten and buckle inwards: invagination.the blastopore will become the anus.the other end of the archenteron will form the mouth of the digestive tube.
9 Frog gastrulationFrog gastrulation produces a triploblastic embryo with an archenteron.Where the gray crescent was located, invagination forms the dorsal lip of the blastopore.Cells on the dorsal surface roll over the edge of the dorsal lip and into the interior of the embryo: involution.As the process is completed the lip of the blastopore encircles a yolk plug.
11 Amniote embryos develop in a fluid-filled sac within a shell or uterus The amniote embryo is the solution to reproduction in a dry environment.chorionamnionembryoallantoisyolk sacExtraembryonic membraneFetal portion of placentaMaternal portion of placentareptile & birdmammal
12 The four extraembryonic membranes are the yolk sac, amnion, chorion, and allantois. Cells of the yolk sac digest yolk providing nutrients to the embryo.The amnion encloses the embryo in a fluid-filled amniotic sac which protects the embryo from drying out.The chorion cushions the embryo against mechanical shocks.The allantois functions as a disposal sac for uric acid.
13 Mammalian Development. Recall:The egg and zygote do not exhibit any obvious polarity.Holoblastic cleavage occurs in the zygote.Gastrulation and organogenesis follows a pattern similar to that seen in birds and reptiles.
14 Differentiation of primary germ layers into tissues and organs. OrganogenesisDifferentiation of primary germ layers into tissues and organs.
20 Morphogenesis in animals involves specific changes in cell shape, position, and adhesion Changes in cell shape usually involves reorganization of the cytoskeleton.
21 The cytoskeleton is also involved in cell movement. Cell crawling is involved in convergent extension.The movements of convergent extension probably involves the extracellular matrix (ECM).ECM fibers may direct cell movement.Some ECM substances, such a fibronectins, help cells move by providing anchorage for crawling.Other ECM substances may inhibit movement in certain directions.
33 BMP in neural tube formation Inhibition of BMP signalingAt end of neurulation the lateral edges of the neural plate fuseThey segregate from the non-neural epithelia to form a neural tubeRoof plate of neural tube now produces BMP. BMP stimulates neural crest cell formationThe CNS arises from a specialized epithelium, the neural plate (1). This process relies on the inhibition of bone morphogenetic protein (BMP) signalling. Folding of the neural plate to produce the neural groove is triggered by the formation of a distinct hinge point in the ventral region (the floor plate; 2). At the end of neurulation, the lateral edges of the neural plate fuse (3) and segregate from the non-neural epithelium to form a neural tube (4). The roof plate and floor plate form at the dorsal and ventral midline of the neural tube, respectively. The roof plate becomes a new organizing centre that produces BMPs, which provide dorsal patterning information. Neural crest cells derive from the dorsal neural tube and migrate out to form the PNS, as well as melanocytes and cartilage in the head. Neural crest cells have been shown to form at an intermediate level of BMP signaling.
40 Guess whom the following grew up to be: A.B.C.D.How Did Rats Grow Wings and Became Bats?Adjust text size:April 19th, 2006, 12:16 GMT| By Vlad TarkoBats are one of the most successful mammals, a fifth of all mammalian species beings bats. They are extremely diverse creatures, but they do have one thing in common: they have wings and fly. Scientists have always been wondering about how bats end up having wings and now the relatively new field of evolutionary developmental biology, or "evo devo" for short, seems to have unraveled the enigma. Karen Sears and Lee Niswander of the University of Colorado Health Sciences Center in Aurora and their colleagues have compared the wings of the earliest known bat fossil, a 50-million-year-old specimen housed at the American Museum of Natural History in New York, with those of three other species of extinct bats and 10 species of modern bats. They found that in all cases the membranous bat wing is supported by the animal's highly elongated third, fourth, and fifth forelimb digits. What surprised them was to discover that the relative length of these three digits to body size has changed very little over the course of bat evolution. In other words, the bats' wings did not seem to have gradually grown larger and larger, but they have evolved quite suddenly. This suggests that the evolution of bat wings was due not to changes in the bone genes themselves but to a change in the gene that regulates the expression of these bone genes. To find what gene might have been involved, the team monitored the development of the bat embryo and compared this development to the development of the mouse embryo. They found that during early development, both bat and mouse forelimb digits grew at about the same rate relative to their overall gestation periods of 120 and 20 days, respectively. However, roughly halfway through gestation, the bat's third, fourth, and fifth forelimb digits suddenly started to grow much faster. In the picture you can see that, at 80 days, the three forelimb digits that will eventually support the bat's wing have already begun to elongate significantly. On the other hand, the same digits in the mouse continued to grow slowly, as did the bat's hind limb digits. This observation has lead scientists to consider that the sudden growth may be due to a gene that coded a certain protein (called Bmp2) responsible for bone growth. They have found that the expression of this gene was indeed 30% higher in the developing forelimbs of bats than it was in mice. This indicated that what probably prompted the appearance of bats from mouse-like rodents was a mutation in the gene regulating the Bmp2 gene. This mutation, that probably happened around 50 million years ago, has caused an abnormal growth of the forelimbs digits. But these early bats instead of succumbing to such a misfortune and dying off proved to be quite able to adapt. They started to use their overdeveloped fingers as wings, and eventually became some of the most successful mammals on Earth.G.F.H.E.
41 Phylum Chordata A. dolphin B. fish C. cat D. human F. Elephant G. SnakeH. batE. Mouse