Evolution is a Remodeling ProcessEvolution is a Remodeling Process

Refinement of Existing AdaptationsRefinement of Existing Adaptations• Complex structures often evolve from

simpler structures.

• Structures do not have to be complicated to be a useful adaptation.

Video

Adaptation of Existing StructuresAdaptation of Existing Structuresto New Functionsto New Functions

• Chitin of arthropods – Arthropods originated in ocean and

exoskeleton used for protection.– As arthropods colonized land,

exoskeleton adapted for additional function: resisting water loss.

• Penguin forelimbs– Penguins are birds and possess wings

that have been modified into flippers.– Penguins live in remote places (flight

offers little advantage for escape/hunting) and food is more abundant in the water than land (strong swimming offers survival advantage).

Evolution and DevelopmentEvolution and Development

• Remodeling can involve changes in the rate or timing of some event in the development of an organism.

• We can investigate these control mechanisms to learn more about how evolution remodels certain features.

• Terrestrial vs. Tree Salamanders– Tree-dwellers have shorter toes and

more webbing.– Tree-dwellers foot growth ends sooner

in development.

Development of Dolphin BlowholeDevelopment of Dolphin Blowhole• In most mammals, the nose opening is located

near the tip of the snout.• In modern dolphins, however, it is located on the

top of the head.• In development, the nose opening shifts from the

tip of the snout to its position on top of the head.

What is evo-devo?What is evo-devo?

• “Evolutionary developmental biology”• Some genes are more like switches than

blueprints, because they function to initiate certain developmental pathways.

• The same switches can activate very different developmental pathways.

• Analogy: power strip vs. normal plugs• Video: Explain Evo-Devo. Fast.