Answer to Question 1The proposed mechanism of natural selection for how living things might evolve (change)
with the passage of time. Darwins main points include: (1) In any group of organisms, more
offspring are produced than can survive to reproductive age. (2) Random variations occur in
all organisms. Some of these traits are inheritable; they can be passed on to offspring. (3)
Some inheritable traits make an organism better suited to its environment (most do not). (4)
Because bearers of favorable traits are more likely to survive, they are also more likely to
reproduce successfully than bearers of unfavorable traits. Favorable traits tend to accumulate
in the population; they are selected. Unfavorable traits are weeded out by competition. (5)
The physical and biological (natural) environment itself does the selection. Favorable traits
that contribute to the organisms success show up more often in succeeding generations (if
the environment stays the same). If the environment changes, other traits become
favorable, and the organisms with those traits live most effectively in the new environment
Answer to Question 2Life on Earth exhibits unity and diversity: diversity because Earth may house as many as 100
million different species (kinds) of living organisms; unity because all species share the same
underlying mechanisms for capturing and storing energy, manufacturing proteins, and
transmitting information between generations. This idea is especially important: In a sense,
all life on Earth is fundamentally the same; its just packaged in different ways. All Earths
life-forms are related; all apparently share a common origin. Earth and life have grown old
together, generation by persistent generation, across some 4 billion years.
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