1) Adaptations are physical or behavioral characteristics that help organisms survive and reproduce in their environments. 2) The fossil record provides evidence that species have changed over time as the Earth has changed, with newer fossil layers containing organisms more similar to present-day species. 3) Comparing anatomical and DNA evidence across living and extinct species, scientists have determined that species are related through common ancestors and have gradually changed over millions of years through the process of evolution.

1. The Evolution of
Living Things
Changes over Time

2. Differences Among Organisms
Adaptation: a characteristic that helps
an organism survive and reproduce in its
environment
Adaptations can be physical, such as a
long neck on a giraffe or striped fur
Adaptations may be behaviors that help
an organism find food (like hunting at
night), protect itself (skunk spraying
noxious smell), or reproduce

3. Examples of Adaptations
The red-eyed
tree frog hides
among a
tree’s leaves
during the day
and comes out
at night

4. The bright coloring of the
strawberry poison arrow frog
warns predators that the frog is
poisonous

5. The smoky
jungle frog
blends into the
forest floor.
This
adaptation
helps the frog
protect itself
from
predators.

6.  It is believed that
a giraffe’s neck
elongated over
time to adapt to
a food shortage.
With a long neck,
a giraffe can
reach the highest
branches for
leaves. This gives
it an advantage
over other
animals.

7. Species: group of organisms that
can mate with one another to
produce fertile offspring
 Groupsof individuals of the same
species living in the same place make
up a population

8. Do Species Change Over Time?
 The species that live on Earth today
range from single-celled bacteria to
multicellular fungi, plants, and
animals
 Scientists think that Earth has
changed a great deal during its
history, and that living things have
changed, too
 Earth is estimated to be 4.6 billion
years old
 Many species have existed over
time, and many have died out

10. Scientists have observed that:
*species have changed over time
*inherited characteristics in populations
have changed over time
*new species have formed—therefore,
newer species descend from older
species
Evolution:
the process in which
populations gradually change over
time

11. Evidence of
 Earth’s crust is arranged in Changes
layers made up of different
kinds of rock and soil Over Time
stacked on top of one
another
 Layers form when
sediments, particles of
sand, dust, or soil are
carried by wind and water
and deposited in an
orderly fashion—
sedimentary rock
 Sometimes, the remains or
imprints of once-living
organisms are found in the
rock—these remains are
called fossils

12.  Fossils
can be a
whole organism,
part of an
organism, or just a
set of footprints

13.  Fossil record: a
historical sequence
indicated by fossils
found in layers of the
Earth’s crust
-organizes fossils by (1)
their estimated ages
and (2)physical
similarities
-fossils found in newer
layers of Earth’s crust
tend to be similar to
present-day organisms

14. Evidence of Ancestry
 The fossil record provides evidence about
the order in which species have existed
 Scientists observe that all living organisms
have characteristics in common and
inherit characteristics in similar ways
 Scientists believe that all living species
descended from common ancestors
-evidence of this is found in fossils and in
living organisms

15.  Scientists examine
the fossil record to
figure out the
relationship
between extinct
and living
organisms
 Models may be
drawn to show
how several
species were
once related

16. Example:
 Scientists
think that
whales and some types
of hoofed mammals,
such as camels and
hippos, have a common
ancestor

17. Examining Organisms
 This ancestor was probably a mammal
that lived on land between 50-70 million
years ago
 Examining an organism carefully can give
scientists clues about its ancestors
 Example: Whales seem very similar to fish,
but whales have live young and breathe
air, which makes them a mammal. These
traits show scientists that whales evolved
from ancient mammals.

18. Scientists use
information
about living
and ancient
species to
sketch out a
“tree of life”
that includes
all known
species

19. Comparing Organisms
 Evidence that groups
of organisms have
common ancestry
can be found by
comparing the
groups’ DNA
 Organismscontain
evidence that
populations and
species undergo
changes in traits and
DNA over time

20. Example:
What does
your arm have
in common
with the front
leg of a cat, a
front flipper
of a dolphin,
or the wing of
a bat?

21.  Thesestructures do
not look alike and are
not used in the same
way
 Under the surface
there are similarities
 Thesesimilarities
suggest that cats,
dolphins, bats, and
humans had a
common ancestor

22.  Over million of years, changes occurred in
the limb bones of the ancestor’s
descendents
 Eventually, the bones performed different
functions in each type of animal

23. Comparing DNA
 Traitsare inherited through DNA’s
genetic code
 Example: the DNA of a house cat is
similar to the DNA of a tiger

24.  Scientists
find that
species that have
many traits in common
do have similarities in
their DNA
 The fact that all
existing species have
DNA supports the
theory that all species
share a common
ancestor