Bio1151b
Chapter
22
Descent with Modification
Charles
Darwin
explained the diversity of life by
of
. through
with
from a common ancestor.
His ideas can be summarized in
inferences based on
observations.
Observation #1:
of
offspring.
Observation #2: Populations tend to remain
in size over
time.
Observation #3: Resources are
limited.
Inference #1 (
for existence): There is a
struggle
for
among individuals of a population.
Observation #4: Members of a
population
exhibit
in their characteristics.
Observation #5: Much of this
variation
is
.
Inference #2 (
selection): Individuals whose inherited traits give them a high probability of surviving and
are likely to leave more
offspring
than others.
Inference #3 (
): A population will gradually accumulate favorable
characteristics
over generations and become more
to its
environment.
Humans have modified other species over generations by
and breeding individuals that possess desired traits. Darwin called this
selection.
Drug resistance in bacteria and viruses such as
HIV
are probably due to
and
for individual organisms that possess the resistance.
anatomical structures, such as the
among mammals, provide evidence of common
ancestry
with
modifications.
Comparative
reveals
anatomical
not visible in adults.
In
, related species tend to be found in the same
area;
unrelated species that occupy similar ecological niches may look similar by
evolution.
Darwin's theory of evolution predicts
forms during the evolution of species, and this is supported by
records.
homologies
provide the latest support for Darwin's theory of evolution.