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Theory of Evolution:
Change in living organisms over many successive generations.
Adaptations :inherited characteristics that increases an organisms
chance of survival and opportunity to reproduce in it’s niche.
Niche: the specific area where an organism inhabits and its role in that
specific area
Founded the theory of natural selection and author of
the book “Origin of Species”.
“It is not the strongest of the species that survives,
nor the most intelligent that survives.
It is the one that is the most adaptable to change.”
-Charles Darwin, Origin of Species
Natural Selection
(struggle for survival)
Reproductive Advantage
 Populations tend to produce more offspring than are
needed to replace the parents. Natural populations
normally maintain constant numbers. There must
therefore be a certain death rate.
 Individuals in a population vary in their phenotype
and therefore, their genotype.
 Factors in the environment will determine which traits are
favorable or unfavorable. Some traits increase a chance for
survival and others do not.
 Biotic factors: amount of food, presence of predators
 Abiotic factors: temperature, amount of water, territory
 The variations (both favorable and unfavorable) are passed
on to offspring. Each new generation will contain
proportionally more descendents from individuals with
favorable traits (“the fittest”) than those with unfavorable.
Favorable trait = adaptation
1. Natural selection involves organisms trying to adapt.
2. Natural selection acts for the good of the species.
3. Natural selection produces organisms perfectly suited to their
4. The fittest organisms in a population are those that are strongest,
healthiest, fastest, and/or largest.
5. Individuals with favorable traits tend to produce more offspring
than those with unfavorable traits. Therefore, over time, favorable
traits become more common within a population found in a
particular environment.
6. The environment determines which traits are favorable and
7. The only thing random about natural selection is the rate and
type of mutations , not the “selection” process.
8. Natural selection is one mechanism of evolution.
Mutations are random: Mutations can
be beneficial, neutral, or harmful for the
organism, but mutations do not “try” to
supply what the organism “needs.”
Not all mutations matter to
Somatic mutations occur in nonreproductive cells and won’t be passed
onto offspring.
The mutation must be inheritable.
 In order to see a change in a
population, natural selection
must take place over multiple
 If the environment changes, the
favorable adaptation may no
longer be favorable.
Geographic Isolation:
A population is separated by a physical barrier into
different environments (ocean, mountains).
2. Different traits will be selected for in each location.
3. Genetic differences will gradually accumulate between
the populations to a point that they can no longer
 The islands are small and close
to each other, but have different
 Darwin noticed several kinds of
small brown birds on the
different Galapagos islands.
 The bird’s beaks looked so
different from each other that
Darwin thought that they were
unrelated…he was surprised to
discover that all of them had a
common ancestor.
 coloration or markings of an animal serving to
warn off predators
 a form of mimicry in which a harmless species has
evolved to imitate the warning signals of a harmful
species in order to avoid predators
Yellow jacket (left)
Clearwing moth (right)
an organism from the past in which present organisms
have evolved from
 Fossil: Preserved remains or evidence of an ancient
 How are fossils formed? An organism dies and is
covered by sediments before being rotted or eaten. It
will become part of the sedimentary layer that becomes
 The lower the layer
is, the older the fossil
 The higher the layer
is, the younger the
fossil is.
 Homologous Structures: organisms with
similar structure, but different function.
 Analogous Structures: Different structure, similar
function. These organisms DID NOT inherit their
structural adaptations from a common ancestor.
 Vestigial Structures: a structure that is no longer used
by an organism, but is found in closely related species.
(Ex. Human appendix and tail bone & whale hip
Comparative Embryology:
Embryos exhibit homologous structures during
certain phases of development, but become totally
different structures in adult forms.
 All vertebrae embryos have a tail and paired pharyngeal
 Fish  gills
 Reptiles, birds, mammals  ear, jaw and throat
 Comparative Biochemistry: Scientists compare patterns of biochemical
molecules (DNA, RNA and amino acid sequences). Evolutionary
theory predicts that molecules in species with a recent common
ancestor should share certain sequences.