1. Biology, 9th ed, Sylvia Mader
Chapter 44
Chapter 44
Animal Development
Animal Development

2. Early Developmental Stages
Outline
Early Developmental Stages
Fertilization
Embryonic Development
Effect of Yolk
Neurulation and the Nervous System
Developmental Process
Cellular Differentiation
Homeotic Genes
Human Embryonic and Fetal Development
Fetal Development

3. Biology, 9th ed, Sylvia Mader
Chapter 44
Fertilization
Animal Development
Fertilization
Several sperm penetrate the corona radiata
Several sperm attempt to penetrate zona pellucida
One sperm enters the egg and their nuclei fuse

4. Embryonic Development
During first stages of development, an organism is called an embryo
Following fertilization, zygote undergoes cleavage
Morula forms blastula with a hollow blastocoel
Germ layers differentiate
Ectoderm
Mesoderm
Endoderm

5. Lancelet Early Development

6. Comparative Development of Mesoderm

7. Neurulation and the Nervous System
Develops from midline ectoderm located just above the notochord
Thickening of neural plate is seen along dorsal surface of the embryo
Neural folds develop on either side of neural groove
Neural grove becomes the neural tube

8. Development of Neural Tube and Coelom in a Frog Embryo

9. Vertebrate Embryo, Cross Section

10. Developmental Processes
Biology, 9th ed, Sylvia Mader
Developmental Processes
Chapter 44
Animal Development
Development requires:
Growth
Cellular Differentiation
Morphogenesis
Adult body cells are totipotent
Each contains all the instructions needed by any other specialized cell in the body
3.B.2: Morphogens stimulate cell differentiation and development.
Morphogenesis produces shape and form of the body; one of the earliest indications is cell movement; later includes pattern formation (how tissues and organs are arranged in the body).

11. Cytoplasmic Influence on Development

12. Induction
The ability of one embryonic tissue to influence the development of another tissue
Developmental path of cells is influenced by neighboring cells

13. Control of Nervous System Development

14. Biology, 9th ed, Sylvia Mader
Model Organisms
Chapter 44
Animal Development
Roundworm, Caenorhabditis elegans
Fruit Fly, Drosophila melanogaster
Mouse, Mus musculus
Fate Maps
Show the destiny of each cell as it arises

15. Development of C. elegans, a Nematode
Biology, 9th ed, Sylvia Mader
Development of C. elegans, a Nematode
Chapter 44
Animal Development
2.E.1: C. elegans development

16. Development in Drosophila, a Fruit Fly

17. Biology, 9th ed, Sylvia Mader
Homeotic Genes
Chapter 44
Animal Development
Homeotic Genes control pattern formation
Organization of differentiated cells into specific three-dimensional structures
Certain genes control whether a particular segment will bear antennae, legs, or wings
Homeotic genes all contain the same particular sequence of nucleotides, the homeobox
Mice and humans have the same four clusters of homeotic genes
They are located on four different chromosomes
3.D.2: Morphogens in embryonic development
Proteins, called morphogens, form gradients that influence patterns of tissue development. Morphogen gradients turn on genes because they are transcription factors that regulate which genes are active in which parts of the embryo in what order.

18. Pattern Formation in Drosophila

19. Extraembryonic Membranes

20. Human Development Before Implantation

21. Human Embryonic and Fetal Development
Human gestation time - time from conception to birth - approximately nine months
Embryonic Development - Months 1-2
Fetal Development - Months 3-9
Extraembryonic Membranes
Chorion
Amnion
Allantois
Yolk Sac

22. Human Embryonic Development

23. Embryonic Development
First Week
Morula transformed into blastocyst
Gives rise to chorion
Second Week
Implanting begins
Gastrulation occurs
Inner cell mass flattened into embryonic disk
Ectoderm and Endoderm differentiate

24. Embryonic Development
Third Week
Nervous system and circulatory system appear
Fourth and Fifth Weeks
Umbilical cord is fully formed
Limb buds appear
Head enlarges
Sense organs more apparent

25. Human Embryo at Beginning of Fifth Week

26. Embryonic Development
Sixth Through Eighth Weeks
Head achieves normal relationship with the body
Nervous system is developed enough to permit reflex actions

27. Structure and Function of the Placenta
A mammalian structure that exchanges materials between maternal and embryonic circulations
Gases
Nutrients
Wastes

28. Anatomy of the Placenta in a Fetus at Six to Seven Months

29. Three Stages of Parturition

30. Biology, 9th ed, Sylvia Mader
Chapter 44
Ending Slide Chapter 44
Animal Development
Animal Development