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					Developmental Biology
What happens during development?
How do we study development?

The visible embryo

Embryology vs Developmental Biology
• Embryology
– Describes the creation of an organism from a fertilized egg

• Developmental biology
– Development never stops
• Metamorphosis • Regeneration • Replacement of skin and red blood cells

Major questions of Developmental Biology
Sperm and Egg Visual by www.PDImages.com

Development
Fertilization Egg and Sperm Gametogenesis

Gametogenesis

Specific Questions of Development
• How does differentiation occur? • How does morphology of organisms develop? • How do organisms Grow? • How do organisms reproduce? • Can organisms “Evolve”? • How does the environment influence development?

How do we study development?
• • • • Anatomical approach Cellular approach Genetic approach Molecular approach

Anatomical and Physiological Questions on Early Stages of Development
• What is happening during each day of development? # of cells? differentiation? • Where is the zygote or embryo during development? • How is the embryo getting nutrients? • Where is embryo waste going?
The visible embryo Other questions?

Cellular Questions
• What types of cells are there? • How does each cell know where it is and what it will become? • What are the cellular signals? • What are the cellular responses? Other questions?

Molecular and Genetic questions
• What genes are responsible for development? • How does timing of gene expression alter development? • What are the mechanisms regulating gene expression? • How do environmental cues influence gene expression and development?

Definitions of terms
• What process occur in the embryo?
– Cell division – Growth – Differentiation – Pattern formation – Morphogenesis

The visible embryo

Cell division and Growth
• Increase in over all size of embryo or organ – From increase in cell number Hyperplasia
– Increase in cell size

Hypertrophy

– Deposition of material surrounding the cells

Differentiation
• Cells become structurally and functionally distinct

Pattern formation
• Body plan • Regional specification
– Body Axes specified – Developmental compartments

8.5 Axes of a bilaterally symmetrical animal

When does pattern formation start?

Morphogenesis
• Creation of structure and form • Cell behavior
– Divide or don’t divide – Adhere or disperse – Change size and/or shape – Fuse with other cells – Die

Early steps of development
Cell division to form blastocysts

No increase in size

http://www.advancedfertility.com/morula.htm


				
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