KEY, Ch. 22 Rdg: Overview, 22.1 & 22.2 (pp 452-460) Neil 9e
1.
With what phrase did Charles Darwin define ‘evolution’? What is the
more modern (though perhaps more narrow) definition of ‘evolution?’
Darwin used the phrase “descent with modification” to refer to evolution.
Today, we would say that evolution is a change in the genetic composition of
a population from generation to generation.
2. Describe how each of the five people (six, really!) noted in the timeline
in Figure 22.2 (p. 453) influenced Darwin’s thinking about evolution.
Hutton: Scottish geologist who proposed that Earth’s geology could be explained by gradual mechanisms
still operating today (e.g. rivers carving canyons).
Malthus: Economist who contended that much of human suffering (famine, disease, etc.) was the
inescapable consequence of the human population’s potential to increase faster than its resource supply.
Lamarck: French biologist probably most famous for explaining that living things had changed over time
through the inheritance of acquired characteristics; that body parts used extensively became larger,
while those that were not used grew smaller. He had other ideas too – some unsubstantiated, some
visionary.
Cuvier: French scientist, studied fossils; noted that the older the rock layer (stratum), the more
dissimilar its fossils were to current life forms. Also noted that some species had gone extinct while
others appeared in the fossil record. Advocated for catastrophism.
Lyell: British geologist advancing principle of uniformitarianism: mechanisms of geologic change are
constant over time and that today’s processes are operating as they did in the past.
Wallace: British naturalist who nearly scooped Darwin! Darwin and Wallace jointly presented their ideas
to science in 1858. It is understood that Darwin worked on the theory of evolution by natural selection
20-30 years longer than Wallace so he gets the major credit.
3. Use the “2 Observations and 2 Inferences” style on p. 458 to explain, as Darwin might have:
How Namib beetles (see p. 452) evolved from
“generic” ancestral beetles
O: Ancestral beetles varied in their headstanding
behavior
O: Beetles produce more offspring than their
environment can support, and many of them perish
I: Those beetles whose headstanding behavior was
more pronounced, allowing them to capture droplets
of fog on their elytra, were more likely to survive
and reproduce, leaving more of their offspring
I: Since more beetles with headstanding behavior
survived and reproduced, the favorable trait of
headstanding accumulated in the population over
generations.
How flower praying mantids (see p. 460) evolved
from “generic” ancestral mantids
O: Ancestral mantids varied in their appearance
O: Mantids produce more offspring than their
environment can support, and many of them perish
I: Those mantids whose bodies more closely
resembled leaves (or flowers), allowing them to
sneak up on their prey insects without being seen,
were more likely to survive and reproduce, leaving
more of their offspring
I: Since more mantids with leaf-like (or flower-like)
bodies survived and reproduced, the favorable trait
of camouflage accumulated in the population over
generations.