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Evolution and development: key points
- The triad of genes, development and environment is responsible for the adult phenotype of an individual organism.
- Developmental plasticity is the capacity to adjust the phenotype arising from a single genotype by changing pathways of development in early life. It allows organisms to maintain or enhance fitness by matching themselves better to different environments, and to adjust to changing circumstances on a timescale intermediate between that of selection and homeostasis.
- The modularity of structure and function allows for duplication and this can provide an important source of evolutionary novelty.
- Epigenetic molecular processes are central to the mechanisms of developmental plasticity.
- Developmental plasticity, which has an adaptive origin, must be distinguished from developmental disruption, which does not. However, some developmentally plastic responses, while being adaptive in origin, can lead to maladaptive outcomes and may result in impaired health later.
- Environmental influences in one generation can influence subsequent generations through these processes.
Waddington’s epigenetic landscape
This metaphor illustrates simply how the programme for development, presumed to be inherent in the genotype, could be modified by environmental influences to take the developing organism down different paths – a concept called canalisation. Inherent in the canalisation metaphor remains the concept that aspects of development are protected from the environment because, even though the developing organism can pass down alternative channels, the sides of these channels are steep so that it cannot diverge from the path. So developmental processes are kept robust, but could also be plastic when required.