Transcript change over time

Evolution
Species
A
group of organisms that can mate
with one another to produce FERTILE
offspring.
Do Species Change Over Time?
 The
Earth is approximately 4.6 billion
years old.
 Over this time Earth has changed in
many ways.
 Have species changed as well???
Evolution
 The
process by which populations
accumulate inherited changes over
time.
CHANGE OVER TIME
Evidence of Evolution
 The
Fossil Record
 Provides evidence about the order in
which evolutionary changes occurred
 Fossils found in the upper (newer)
layer of Earth’s crust tend to be more
recent and reflect present day while
fossils deeper in Earth’s crust are
less like present-day organisms.
What is a Fossil???
 Solidified
remains or imprints of
once-living organisms.
 Form when a dead organism is
covered by a layer of sediment.
Why Are There Gaps in the Fossil
Record
 Very
specific conditions are needed
to form fossils and these conditions
are not always met.
– Oxygen cannot be present
– Organism must be buried in fine
sediment.
Further Evidence of Evolution
 Vestigial
Structures
– These are the remnants of once-useful
structures.
More Evidence
 Comparing
Skeletal Structures
 Comparing DNA
 Comparing Embryonic Structures
Formation of a New Species

Can happen by following three steps:
– Separation: Portion of the population
becomes isolated by a new canyon, mountain
range, etc.
– Adaptation: As the environment changes, the
population must do so as well.
– Division: Over many hundreds of years,
thousands of years, or even longer the two
populations become so different that they can
no longer interbreed and are thus different
species.
 Some
finches left the mainland and
reached one of the islands.
– Separation
 The finches reproduced and adapted to
the environment.
– Adaptation
 Some finches flew to a second island.
– Separation
 The finches reproduced and adapted to
the different environment
– Adaptation
Darwin’s Finches
 Some
finches flew back to the first
island but could no longer interbreed
with the finches there (division).
 This process may have occurred over
and over again as the finches flew to
the other islands.