Chapter 4 Outline

The Physiology of Immature Animals Always Differs from That of Adults

Introduction to Phenotypic Plasticity and Epigenetics

Phenotypic Plasticity during Development

  • Environmental effects during development may arise from programmed responses to the environment or may be forced by chemical or physical necessity
  • Insect polyphenic development underlies some of the most dramatic cases of phenotypic plasticity
  • Other animals besides insects also sometimes exhibit polyphenic development

Epigenetics

  • Two major mechanisms of epigenetic marking are DNA methylation and covalent modification of histone proteins
  • Epigenetic inheritance can be within an individual or transgenerational
  • Epigenetic marking plays a key role in tissue differentiation during ordinary development
  • Evidence increasingly points to epigenetic control of polyphenic development
  • Epigenetic marking may account for lifelong effects of early-life stress
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