Suites of Developmental Characters - General Zoology - Lecture Slides, Slides of Zoology

Download Suites of Developmental Characters - General Zoology - Lecture Slides and more Slides Zoology in PDF only on Docsity! Principles of Development Chapter 8 Docsity.com Suites of Developmental Characters  Two major groups of triploblastic animals:  Protostomes  Deuterostomes  Differentiated by:  Spiral vs. radial cleavage  Regulative vs. mosaic cleavage  Blastopore becomes mouth vs. anus  Schizocoelous vs. enterocoelous coelom formation. Docsity.com Deuterostome Development  Deuterostome means second mouth.  The blastopore becomes the anus and the mouth develops as the second opening. Docsity.com Deuterostome Development  The coelom is a body cavity completely surrounded by mesoderm.  Mesoderm & coelom form simultaneously.  In enterocoely, the coelom forms as outpocketing of the gut. Docsity.com Deuterostome Development  Typical deuterostomes have coeloms that develop by enterocoely.  Vertebrates use a modified version of schizocoely. Docsity.com Protostome Development  Protostome means first mouth.  Blastopore becomes the mouth.  The second opening will become the anus. Docsity.com Protostome Development  In protostomes, a mesodermal band of tissue forms before the coelom is formed.  The mesoderm splits to form a coelom.  Schizocoely  Not all protostomes have a true coelom.  Pseudocoelomates have a body cavity between mesoderm and endoderm.  Acoelomates have no body cavity at all other than the gut. Docsity.com Two Clades of Protostomes  Lophotrochozoan protostomes include annelid worms, molluscs, & some small phyla.  Lophophore – horseshoe shaped feeding structure.  Trochophore larva  Feature all four protostome characteristics. Docsity.com Building a Body Plan  Uneven distribution of substances in the egg called cytoplasmic determinants results in some of these differences.  Position of cells in the early embryo result in differences as well.  Induction Docsity.com Restriction of Cellular Potency  In many species that have cytoplasmic determinants only the zygote is totipotent, capable of developing into all the cell types found in the adult. Docsity.com Restriction of Cellular Potency  Unevenly distributed cytoplasmic determinants in the egg cell:  Are important in establishing the body axes.  Set up differences in blastomeres resulting from cleavage. Docsity.com Induction  Induction is the capacity of some cells to cause other cells to develop in a certain way.  Dorsal lip of the blastopore induces neural development.  Primary organizer Docsity.com Spemann-Mangold Experiment  Transplanting a piece of dorsal blastopore lip from a salamander gastrula to a ventral or lateral position in another gastrula developed into a notochord & somites and it induced the host ectoderm to form a neural tube. Docsity.com Building a Body Plan  Cell differentiation – the specialization of cells in their structure and function. Morphogenesis – the process by which an animal takes shape and differentiated cells end up in their appropriate locations. Docsity.com Formation of the Vertebrate Limb  Inductive signals play a major role in pattern formation – the development of an animal’s spatial organization. Docsity.com Formation of the Vertebrate Limb  The molecular cues that control pattern formation, called positional information:  Tell a cell where it is with respect to the animal’s body axes.  Determine how the cell and its descendents respond to future molecular signals. Docsity.com Formation of the Vertebrate Limb  The wings and legs of chicks, like all vertebrate limbs begin as bumps of tissue called limb buds.  The embryonic cells within a limb bud respond to positional information indicating location along three axes. Docsity.com The Cytoskeleton, Cell Motility, and Convergent Extension  Changes in the shape of a cell usually involve reorganization of the cytoskeleton. Docsity.com Changes in Cell Shape  The formation of the neural tube is affected by microtubules and microfilaments. Docsity.com Cell Migration  The cytoskeleton also drives cell migration, or cell crawling.  The active movement of cells from one place to another.  In gastrulation, tissue invagination is caused by changes in both cell shape and cell migration. Docsity.com The Common Vertebrate Heritage  Vertebrates share a common ancestry and a common pattern of early development.  Vertebrate hallmarks all present briefly.  Dorsal neural tube  Notochord  Pharyngeal gill pouches  Postanal tail Docsity.com Amniotes  The embryos of birds, reptiles, and mammals develop within a fluid-filled sac that is contained within a shell or the uterus.  Organisms with these adaptations form a monophyletic group called amniotes.  Allows for embryo to develop away from water. Docsity.com Amniotes  In these three types of organisms, the three germ layers also give rise to the four extraembryonic membranes that surround the developing embryo. Docsity.com The Mammalian Placenta and Early Mammalian Development Most mammalian embryos do not develop within an egg shell.  Develop within the mother’s body.  Most retained in the mother’s body. Monotremes  Primitive mammals that lay eggs.  Large yolky eggs resembling bird eggs.  Duck-billed platypus and spiny anteater. Docsity.com The Mammalian Placenta and Early Mammalian Development Marsupials  Embryos born at an early stage of development and continue development in abdominal pouch of mother.  Placental Mammals  Represent 94% of the class Mammalia.  Evolution of the placenta required:  Reconstruction of extraembryonic membranes.  Modification of oviduct - expanded region formed a uterus. Docsity.com Mammalian Development  The eggs of placental mammals:  Are small and store few nutrients.  Exhibit holoblastic cleavage.  Show no obvious polarity. Docsity.com Mammalian Development  The extraembryonic membranes in mammals are homologous to those of birds and other reptiles and have similar functions. Docsity.com Mammalian Development  Amnion  Surrounds embryo  Secretes fluid in which embryo floats  Yolk sac  Contains no yolk  Source of stem cells that give rise to blood and lymphoid cells  Stem cells migrate to into the developing embryo  Allantois  Not needed to store wastes  Contributes to the formation of the umbilical cord  Chorion  Forms most of the placenta Docsity.com Organogenesis  Various regions of the three embryonic germ layers develop into the rudiments of organs during the process of organogenesis. Docsity.com Derivatives of Ectoderm: Nervous System and Nerve Growth  Neural crest cells pinch off from the neural tube.  Give rise to  Portions of cranial nerves  Pigment cells  Cartilage  Bone  Ganglia of the autonomic system  Medulla of the adrenal gland  Parts of other endocrine glands  Neural crest cells are unique to vertebrates.  Important in evolution of the vertebrate head and jaws. Docsity.com Derivatives of Endoderm: Digestive Tube and Survival of Gill Arches  During gastrulation, the archenteron forms as the primitive gut.  This endodermal cavity eventually produces:  Digestive tract  Lining of pharynx and lungs  Most of the liver and pancreas  Thyroid, parathyroid glands and thymus Docsity.com Derivatives of Endoderm: Digestive Tube and Survival of Gill Arches  Pharyngeal pouches are derivatives of the digestive tract.  Arise in early embryonic development of all vertebrates.  During development, endodermally-lined pharyngeal pouches interact with overlying ectoderm to form gill arches.  In fish, gill arches develop into gills.  In terrestrial vertebrates:  No respiratory function  1st arch and endoderm-lined pouch form upper and lower jaws, and inner ear.  2nd, 3rd, and 4th gill pouches form tonsils, parathyroid gland and thymus. Docsity.com