BIOLOGY 1B Lecture Notes - Lecture 10: Venus Flytrap, Phyletic Gradualism, Exaptation
12 Jun 2018
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Lecture 10: Macroevolution:
9/15
• Exaptation and tinkering:
o Pitcher plant drowns ants but spider is able to go down and steal the dead insects and eat it
o Cooptation of an existing structure for use in a new functional context
o How complex structures evolve
▪ Evolutionary novelties that can generate great success and cause speciation events and
differentiation and lineages
• Neomorphs in evolution tend to have a foundation in other organs that evolved
in adaptation to other circumstances or developed form organs that did not
evolve for any specific function but arose as a byproduct and exaptation process
capitalizes on old structures and rebuilds old structures into something new
again
o Concept of tinkering (bricoler)
o Leaves are fuzzy and have little hairs; those hairs have triggers in
Venus flytrap and trap closes to trap insects
▪ Led to whole new evolutionary entity
o Sundews: sticky trichomes to capture insects
▪ Tend to grow in nutrient poor environment; capitalize on
insect material to survive
• Origin of flight in birds
o Involves feathers; unique to big group of related organisms that includes birds
o Archaeopteryx
▪ Feathers on tail and legs
▪ Asymmetrical flight feathers
▪ Other feathers on body are symmetrical or downy
▪ Many fossils illustrate richness of feathers
▪ Feathers used for flight and warmth but also sexual dimorphism and intersexual
selection(not original function tho)
• Feathers exapted for reproduction
• Not evolved for flight; but exapted for it
• Tempo and Mode of evolution
o Phyletic gradualism: a model of evolution which theorizes that most speciation is slow, uniform
and gradual
o Punctuated equilibrium: explain evidence in fossil record
▪ Long periods of stasis of lack of evolutionary change interrupted by rapid bursts of
change
▪ Examples:
• Redwood trees
• Mollusks in Africa
o Morphological stasis: largely unchanged at phenotypic level for hundreds of years
o Both punctuation and gradualism are important
• Levels of selection
o Species selection: creates macroevolutionary change thorugh differential rates of replication and
extinction of lineages
• Macroevolution: large scale evolution over geologic time that results in the formation of new taxonomic
groups and major change sin the tree of life
o Deep geological time school
• Evolutionary developmental biology: the study of developmental biology to shed light on evolutionary
dynamics
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