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Evolution-
Changes Over Time
Evidence for Evolution
Fossil Evidence
Petrifaction- turned into stone
Casts and molds
Actual remains
Traces- imprints
The fossil record is supported by the
Principle of Superposition
Fossils found in lower(older) rock layers are
simpler than upper (younger) layers
Types of fossil organisms change from one
layer to the next
The fossil record is incomplete- not every
life-form left fossil remains
Many fossils show strong similarities to
existing organisms.
Evidence from anatomy
Comparative anatomy- comparing similar
structures from different species of
organisms. These similar parts are called
homologous structures, they indicate
whether the organisms have a common
ancestor.
Organisms inherit structures from
ancestors, they are modified over
time ,but still resemble those of a
common ancestor.
The greater number of homologous
structures that organisms share, the
closer the relationship among them
(divergence)
Analogous Structures – different structures, similar
functions – (convergence)
vestigial organs- structures that have
no function in the organism but may
have been used by ancestors.
Evidence from embryology
and biochemistry
Comparing and contrasting embryos
of organisms. The more similar the
embryos the more closely they are
related
.
Comparative biochemistry- some
scientists believe this provides the
most fundamental evidence to
support evolution
.
comparing amino acid codes in
proteins of living organisms.
the closer the amino acids are in
similarities the more recent the
common ancestor.
Genetic Evidence- Biologists
analyze the base sequences of
DNA comparing with DNA that
controls similar traits in another
organism
.
Direct observation- Penicillin;
bacteria became resistant.
Pesticides; insect pests have
become resistant
.
Adaptation and Speciation
DivergenceEvolution of a species into two
or more different species
.
Convergencetwo unrelated species produce
offspring with similar traits- (fish,
dolphins)
Adaptationan inherited trait that
promotes survival and
reproduction
Behavioral adaptationsinvolve reactions to the
environment , (migration)
Morphological adaptationsinvolve an organisms
anatomy. Affecting structures
in the body.
Coloration
cryptic- camouflage
warning- bright colors to advertise
danger
industrial melanism- dark and light
peppers moths
Physiological adaptations- involve
an organisms metabolism
Skunk- odor
Octopus- ink
Speciation
Biological definition of Species:
A group of populations whose members have
the potential to interbreed in nature and
produce viable, fertile, offspring with members
of other such groups.
Isolation
Geographic isolation- separation
of breeding populations by a
physical or geological feature. (
mountain range, ocean)
Galapagos Islandsfinches evolved to be distinct
species as they adapted to the
unique environments on the
islands they inhabited
.
Kiabab ForestSquirrels became separated by
the Grand Canyon and
developed into separate species
due to the differentenvironments
on either side of the Grand
Canyon
Reproductive Isolationany barrier to interbreeding
.
Adaptive radiationevolution of many species
from a common ancestor.
Evolutionary Theories
Jean Baptiste LaMarakgiraffes had short necks. These Giraffes
gradually stretched their necks and
their offspring inherited their slightly
longer necks, over time this led to the
development of the very long-necked
giraffe that is existence today.
Darwin’s Explanation- there were both
long and short-necked giraffes, the
environment changed making it so that
only the long-necked giraffe was well suited
to its environment. This made it so that only
the long necked giraffe survived to pass the
long-neck trait to its offspring. The shortnecked giraffe could not survive in the new
environment so they died out.
*Darwin did not call this evolution,
but Natural Selection . Natural
selection states that the the traits
to its offspring, thus organism best
adapted to the environment will
survive to pass maintaining the
beneficial trait in the population
.
Dating Fossils
Relative Dating- Using the fossil record
to determine relative age of organisms.
Absolute Dating
Radioactive dating- using radioactive
isotopes to determine ages of once
living organisms
o Carbon Dating- Carbon will
decay into Nitrogen over time. Half
of the Carbon 14 in a sample will
decay into Nitrogen 14 in 5,730
years, this is referred to as a
radioactive half-life
Carbon Dating is only valid in
samples up to 20,000 years old.
Uranium and Potassium
isotopes are used to date fossils
that are older. These isotopes can
be used to date objects that are
millions of years old
.