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Slide 2 Development Biology I From Zygote to Fetus Slide 3 Development n. n Development is a continual process, from conception to death. Slide 4 Development n n It is a series of changes sn organism undergoes in reaching its final, adult form. n n There are more marked changes during the embryonic period of life, which include: cell division cell differentiation morphogenisis (from unicellular to multicellullar) Slide 5 Fertilization n n When egg and sperm fuse. n n Fertilization reinstates the diploid number of chromosomes in the organism. n n It triggers a series of reactions in the egg. Slide 6 Zygote n A fertilized egg, or a diploid cell. Slide 7 Cleavage n n A succession of rapid cell divisions that produces a ball of cells from the zygote. n n During these rapid divisions, the cyst of cells remains the same size. 4 cells Slide 8 8 cells Slide 9 Cleavage & Blastula n n It produces a solid ball of cells, called the morula. n n The morula forms into a hollow ball of cells we call the blastula. Slide 10 Blastula n The fluid filled area in the center of the blastula is called the blastocoel. n Its a lot like the air in a ball. Slide 11 Blastopore, & Archenteron n n A blastopore form on the surface of the blastula when a group of cells begins to move inward. n n The new inner cavity created by the blastopore is called the archenteron. Slide 12 WOW! Slide 13 Gastrula n n Cup-shaped stage. n n When the blastopore invaginates, or buckles inward creating two layers. n n The process called gastrulation. Slide 14 Gastrula Slide 15 Slide 16 Slide 17 Slide 18 Differentiation n n Ectoderm: outermost layer n n Mesoderm: middle layer n n Endoderm: innermost layer Slide 19 Slide 20 Animal vs. Vegital Pole Slide 21 Neural Tube Formation Slide 22 Gastrulation and Neural Tube Formation in a chick embryo Slide 23 Slide 24 Neural Tube Formation Slide 25 Slide 26 Human Blastula Slide 27 Implantation & Formation of Amniotic Cavity Slide 28 Human Connection Slide 29