Bio II Notes 4/21
Bio II Notes 4/21 BIO 1144
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This 3 page Class Notes was uploaded by Rocket on Saturday April 23, 2016. The Class Notes belongs to BIO 1144 at Mississippi State University taught by Thomas Holder in Spring 2016. Since its upload, it has received 16 views.
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Date Created: 04/23/16
Oogenesis Polar bodies: Non functional gametes Mechanisms for ridding extra cells with chromosomes Ovum: 1N= 23 Egg = female gamete Fertilization: 1N Egg + 1N Sperm = 2N Zygote (1N=23) (1N=23) (2N=46) (fertilized egg) Animal Development Ch. 52 +Embryonic development: Cellular differentiation: Cells become specialized Most animals have similar embryonic development processes Embryo in Advanced animals have 3 germ layers/ triploblastic development +5 Stages of Development Fertilization Cleavage Gastrulation Neurulation neural tube dev. Organogenesis *Some animals may also include the metamorphosis of larval form into adult form ❏ Fertilization Internal or external, two haploids fusing to form a diploid 1N Sperm Nucleus + 1N Egg Nuclei → Fuse to form 2N Zygote (fert. egg) ● Cleavage Repeated cell division cycles but without cell growth Blastula is the structure and each cell within is called a blastomere Yolk slows down division, that's why top of blastula is more divided than bottom of blastula because yolk is found towards the bottom, creating polarity 2 Poles: +Poles determines future axes of embryo Vegetal: More yolk, Less cytoplasma often larger but fewer blastomere Animal: Less yolk, More cytoplasma, often smaller but more blastomere +Meroblastic Cleavage Partial/ incomplete cleavage ONLY the Animal Pole divides Blastoderm: “flattened disk of cells” Mostly in bird and fish +Holoblastic Cleavage Complete cell division producing two equal blastomeres with the 1st division Mammals: Fertilization + Cleavage immediately starts in oviduct EXCEPT in bats Fertilized Egg implants on uterine wall Maternal Factors first direct the process and form the placenta Near end of cleavage, Maternal factors play less of a role and it is the embryo directing the shifts ➢ Gastrulation Blastula (Hollow Ball) → Gastrula with 3 germ layers and primordial germ cells +Triploblastic Endoderm: forms epithelial lining of gut tract, liver, pancreas, bladder, lungs, respiratory tube, thyroid gland (mostly respiratory system) Mesoderm: forms notochord, blood, connective tissues, heart, muscles, kidneys, appendages Ectoderm: forms neural tube and epidermis +Invagination : starts when blastopore is created Blastopore: band of tissue “pinches in” to create an opening Archenteron: displaces blastocoel to become digestive tract +Primordial Germ cells (PGC) Specialized cells that migrate to future site of gonads Gonads produce gametes PGC may arise independently from the 3 germ layers +2 functions: Protect and propagate genetic content of species Undergo meiosis to produce gametes +Notochord Derived from mesoderm, the structure provides rigidity along dorsal axis of embryo Defines Phylum Chordata Produces signaling proteins to establish tissue patterns, to form organs Involved in Hox Gene development
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