Chapter 40 Animal Reproduction and Development Asexual Reproduction Cloning the parent plant Lack of variation disadvantage Sexual Reproduction Stages in reproductive history of an organism Includes haploid n and diploid 2n states Time spent in n or 2n varies Meiosis each gamete varies in genetics How does it cause genetic variation during crossing over metaphase 1 Where does meiosis take place in the reproductive organs What is the end result gametes Oogenesis o Nucleus acrosome full of enzymes mitochondria produce ATP for sperm flagella maternal factors Germ cells are in the lining of the yolk sac then migrate to the gut tube then to the gonads direct early developmental functions Migration of Germ Cells to Gonads Primordial germ cell to sperm Germ cells held in the seminiferous tubule o Cell types Sertoli cell Primordial Germ cell to sperm Beginnings in the embryonic ovary then the ovary Begins at meiosis 1 stops 10 15 years meiosis 2 stops until fertilization finishes meiosis 2 o Follicle cells oocytes ovum Events of Fertilization Contact and recognition of gametes Sperm binding and entry into egg Fusion of genetic material Activation of egg metabolism External Fertilization coral reef spawning Acrosomal Reaction acrosome at the head of the sperm the enzymes burst out and eat away the egg jelly until it interacts with the sperm binding protein on the egg the sperm and egg fuse o Cortical Gradnules Cortical Reaction once they fuse the IP3 molecules allow release of calcium ions from the endoplasmic reticulum activates exocytosis Egg Jelly within are molecules that create a gradient Chemotactic gradient Chemotactic Gradient how the right sperm finds the right egg External Fertilization Human Fertilization Sperm 23 chromosomes Egg 23 chromosomes Fusion creates zygote Stages of Animal Development Gametogenesis process of creating gametes sperm and oocyte 1n Fertilization fusion of a sperm and egg 2n Cleavage Stage o Blastula entire thing blastomere one cell blastocoel inside on top animal pole blastopore o Cell divisions without growth o Yolk meroblastic incomplete birds fishes holoblastic complete mammals not a part vs becoming a o Cleavage to Blastocyst 1 4 d 2 cell 16 cells stage cells divides every 12 18 hr Zygotic genes activated invagination part of the embryo 4 8 cell stage Gastrulation Stage formation of germ layers via cell movement o Cell Movements invagination cells pulled interior involution sheet of cells covering another sheet ingression individual cells move into embryo delamination Epiboly cells cover exposed cells Neurulation Stage neural plate neural groove neural tube Organogenesis Stage o Week 3 4 formation of brain and spinal cord o Week 4 formation of heart eye and ear limbs o Week 8 end of embryogenesis in humans Larval Immature adolescence Adult Germ Layers from Gastrula ectoderm mesoderm endoderm germ cells Pregnancy in placental mammals Corpus Luteum maintains uterine lining Placenta develops after implantation and has fetal and maternal tissues Birth depends on Positive Feedback Loop Oxytocin stimulates stronger uterine contractions Stages of Labor Cervix dilates Uterine contractions for delivery Placenta is delivered