1. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 49 Animal Development

2. 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

3. 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

4. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Fertilization

5. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development The cortical reaction

6. 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

7. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cleavage and gastrulation in amphioxus

8. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Spiral cleavage in an annelid embryo

9. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cleavage pattern in a frog egg

10. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cleavage in a bird embryo

11. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Cytoplasmic determinants in frog development

12. 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

13. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Gastrulation in a frog embryo

14. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Gastrulation in birds

15. 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

16. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Fate of the germ layers formed at gastrulation

17. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Development of the human nervous system

18. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Formation of the heart in birds and mammals

19. 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

20. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Extraembryonic membranes

21. 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

22. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Implantation and early development in the uterus

23. 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

24. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Developmental events in the human embryo

25. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development The second month of development

26. Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 49 Animal Development Human fetus at ten weeks

27. 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