SCILIVSY 12 Chapter Notes - Chapter 5-6: Heredity
Course CodeSCILIVSY 12
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SLS 12 Section 3
Name: Alex Simon
The Origin of Species
Chapter 5: Laws of Variation
The effects of “use” and “disuse” seem to puzzle Darwin. What are the
observations that he trying to explain and what are the competing hypotheses?
Darwin notes the role that use and disuse play as species evolve and certain
traits and genes are passed down to offspring. Darwin mentions birds with
varying wing sizes and strengths that have naturally developed that way due to
their flying/traveling habits and low vision for cave-dwelling animals. He attempts
to explain that in addition to advantageous variations, unused organs or traits can
also diminish or disappear over time. In addition to the effects that certain habits
have on a species, these effects must be inherited in order for the process of
natural selection to be successful. The competing hypotheses that Darwin
discusses include the natural selection of variations gained through heredity
versus the effects that certain habits have on a species. Darwin concludes that
traits/variations gained through heredity are more dominant than the effects of
habit. Darwin goes on to hypothesize that due to the susceptibility of organs to
variation, species could not have been created independently.
Chapter 6: Difficulties On Theory
Darwin discusses the evolution of the eye? What is his point in doing so?
Darwin discusses the evolution of the eye to show that over time variations can
become more and more complex until the optimal variation for a specific
environment is created. The eye has continually changed over time showing that
these changes do not happen immediately and that certain organs have
undergone variation after variation to arrive where they are today. Darwin also
uses the eye as an example to show that natural selection is the primary method
of passing on variations.
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