CH_37_STUDENT_OUTLINE[1]

CH_37_STUDENT_OUTLINE[1] - Chapter 37 Animal Development...

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Unformatted text preview: Chapter 37: Animal Development What Is Animal Development? • The process by which an animal proceeds from fertilized egg through adulthood and eventual death • Animals demonstrate two possible forms of development – Indirect development – Direct development Indirect Development • When the juvenile has different morphology from adult – Most invertebrate and some vertebrate (amphibians) – Adults make large number of eggs, each with a small yolk (food reserve) – An immature larva emerges from egg – Metamorphosis produces sexually mature adults larva adult adult larva larva adult adult larva What type of development is this? How does it differ from the other type? Direct Development • When the juvenile resembles the adult form – Reptiles, birds, mammals, and some invertebrates – Newborn is a sexually immature version of adult – Adults produce fewer offspring, but are more developed What type of development is this? How does it differ from the other type? Reptiles, Birds, and Mammals Produce Similar Extraembryonic Membranes • Reptiles, birds, and mammals produce amnionic eggs – Embryo encased in protective shell and liquid-filled space – Acts as “private pond” – Allows the embryo to be less dependent on the external environment for development Reptiles, Birds, and Mammals Produce Similar Extraembryonic Membranes • Amnionic eggs contain 4 extra-embryonic membranes: – Chorion : lines shell, involved with O2 and CO2 exchange with environment – Amnion : encloses embryo in watery environment – Allantois : surrounds and isolates wastes – Yolk sac : contains stored food Reptile Mammal shell yolk sac allantois embryo amnion chorion Reptile Mammal shell yolk sac allantois embryo amnion chorion What role does each membrane play? Difference between shelled & non-shelled eggs? How Does Development Proceed? • Multistage process including: 1. Cleavage 2. Gastrulation 3. The formation of adult structure 4. Sexual maturation Cleavage Begins the Process • Cleavage : – Zygote divides mitotically without an increase in size – A solid round of ball of cells is formed ( morula ) – The morula develops an internal cavity ( blastocoel ) • Becomes a blastula Gastrulation Forms Three Tissue Layers • An indentation ( blastopore ) forms and cells fold inward to form 3 layers: – Endoderm : inner layer; digestive and respiratory tracts – Mesoderm : middle layer; muscle and sceleton – Ectoderm : outer layer; epidermis, circulatory, and nervous system • A 3-layered embryo ( gastrula ) forms Adult Structures Develop • Organs form ( organogenesis ) from each embryonic cell layer: – Organs “sculpted” by programmed death of excess cells – (1) Some cells die unless they receive a chemical “survival signal” (only motor neurons that connect with muscle live) – (2) Some cells live unless they receive a chemical “death signal” (webbing in human toes) Sexual Maturation Is Controlled by Genes and the Environment...
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This document was uploaded on 10/26/2011 for the course BIOL 1001 at LSU.

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CH_37_STUDENT_OUTLINE[1] - Chapter 37 Animal Development...

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