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22.1 Early Developmental Stages
Development begins when a sperm fertilizes an egg.

The first stages of embryonic development in animals lead to the establishment of the embryonic germ layers.

The presence of yolk affects the manner in which animal embryos go through the early developmental stages.

In vertebrates, the nervous system develops above the notochord after formation of a neural tube.
1. What is the role of the acrosome during fertilization?

2. In what way does the amount of yolk in an egg make a difference during development?
Essential Study Partner
Cell Differentiation

Art Quiz
Gastrulation - Mammal

General Biology Weblinks
Developmental Biology

Case Study
22.2 Developmental Processes
Cytoplasmic segregation and induction help bring out cellular differentiation and morphogenesis.

Developmental genetics has benefited from research into the development of Caenorhabditis elegans, a roundworm, and Drosophila melanogaster, a fly.

Homeotic genes are involved in shaping the outward appearance of animals.
3. Explain what is meant by "cellular differentiation" and "morphogenesis."

4. What is the function of homeotic genes?
Art Quizzes
Embryos and Evolutionary History
Allometric Growth

Study Guide
Mammalian Development I
22.3 Human Embryonic and Fetal Development
Humans, like chicks, are dependent upon extraembryonic membranes that perform various services that contribute to development.

Human development consists of embryonic and fetal development.

Humans are placental mammals; the placenta is a unique organ where exchange between fetal blood and mother's blood takes place.

Birth is a multistage process that includes delivery of the child and the extraembryonic membranes.
5. In what way are extraembryonic membranes evolutionarily significant?

6. During what stage of development are all the main organ systems present if not fully developed?
Essential Study Partner
Early Development
Human Development
Hormones and Pregnancy
Preembryonic Development
Embryonic & Fetal Development

Art Quizzes
Extraembryonic Membranes - Mammalian Embryo (1)
Extraembryonic Membranes - Mammalian Embryo (2)

Labeling Exercises
Human Extraembryonic Membranes (38.0K)
Anatomy of the Breast (36.0K)
22.4 Human Development after Birth
Investigation into aging shows hope of identifying underlying causes of degeneration and prolonging the health span of individuals.
7. What habits can be adopted to ensure that an individual ages healthfully?
Essential Study Partner
Postnatal Period
Aging - Skin

Case Studies
Treatment of Critically Ill Newborns

Inquiry into LifeOnline Learning Center with Powerweb

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