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marine copepod species invaded freshwater 60 yrs ago marine populations can’t tolerate freshwater invaders had to evolve tolerance to freshwater. Selective breeding & direct observation experimental evolution; rapid evolution in nature.
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Selective breeding & direct observation
experimental evolution; rapid evolution in nature
we’ve also seen rapid evolution of antibiotic resistance, pesticide resistance
Upon returning home, Darwin began to work through his notebooks from
the voyage and began to consider how species could change.
Influenced by reading:
Charles Lyell - geologist; emphasized uniformity through time:
slow gradual change leading to large accumulated change
Adam Smith - economist; thought competition could regulate society
Thomas Malthus - economist; potential for human population growth;
observation of overproduction of offspring by plants and animals
accumulated over long periods of time (Lyell), could to lead to new species
* We now know that competition isn’t the only source of natural selection.
** In Darwin’s day, nobody understood inheritance because Mendel’s work
wasn’t discovered until 1900.
prodded by some scientific competition
Meanwhile, Alfred Russel Wallace…
- had been on collecting trips to the Amazon and Malaysia
- had read Malthus
- independently came up with the concept of natural selection in 1858
- promptly sent a letter explaining his ideas to Darwin (who still
hadn’t gone public with his theory)
Darwin’s friends brokered a compromise…
- the ideas of Wallace and Darwin were presented together in 1858,
- in 1859 Darwin published a “short” version of the book he was
working on: On the Origin of Species by Means of Natural Selection
This process, natural selection on individuals, results in changes
in the proportion of the population with certain variations.
fitness – organism’s ability to survive and reproduce in its environment
adaptation – trait that increases fitness and has evolved by natural
adapt, adaptation – process of evolving traits, through natural selection,
that increase fitness
adaptive – describes a trait that increases fitness
exaptation (preadaptation) – trait that increases fitness through a
particular function, but has not evolved for that function;
an existing trait that is used for a new function
constraint – factor that slows or prevents evolution of an optimal trait