Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 49 Animal Development
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Four processes of fertilization Contact and recognition between noncellular egg coverings and sperm Sperm entry is regulated Fertilization actives the egg Sperm and egg pronuclei fuse and initiate DNA synthesis
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Fertilization in echinoderms Coverings of echinoderm eggs –Vitelline envelope and jelly coat Sperm undergoes an acrosome reaction, which facilitates penetration of the egg coverings Followed by a fast block to polyspermy and a slow block to polyspermy
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Fertilization
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development The cortical reaction
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Early development of the fetus The zygote undergoes cleavage –Rapid cell divisions with a growth phase –Partitions the zygote into blastomeres Cleavage forms the morula and then usually the blastula
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cleavage and gastrulation in amphioxus
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Spiral cleavage in an annelid embryo
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cleavage pattern in a frog egg
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cleavage in a bird embryo
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cytoplasmic determinants in frog development
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Gastrulation Process by which the blastula becomes a three-layered embryo or gastrula –Zygote –Early cleavage stages –Morula –Blastula –Gastrula
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Gastrulation in a frog embryo
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Gastrulation in birds
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Organogenesis Gastrulation leads to organogenesis, or organ formation Cells of the three germ layers –Continue the processes of pattern formation –Leads to the formation of specific structures
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Fate of the germ layers formed at gastrulation
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Development of the human nervous system
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Formation of the heart in birds and mammals
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development In terrestrial vertebrates, the three germ layers give rise to four extraembryonic membranes Chorion used in gas exchange Amnion, a fluid-filled sac Allantois, which stores wastes Yolk sac, which makes food available to the embryo
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Extraembryonic membranes
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Early human development Fertilization occurs in the oviduct Cleavage takes place as the embryo moves down the oviduct toward the uterus The blastocyst undergoes implantation in the endometrium The umbilical cord connects the embryo to the placenta
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Implantation and early development in the uterus
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Prenatal and postnatal life Human prenatal development requires 266 days –Organogenesis begins during the first trimester and continues throughout –After the first two months, the embryo is referred to as a fetus –The neonate undergoes rapid adaptations, especially in the respiratory and digestive systems
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Developmental events in the human embryo
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development The second month of development
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Human fetus at ten weeks
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Aging Marked by a decrease in homeostatic response to stress All body systems decline with age, but not at the same rate –Examples include loss of taste buds and axons in spinal nerves