The Theory of Evolution

1
The Theory of Evolution

• Evidence Used For Its Study
• Notes from Mrs. Miller

2
Evolution Vocabulary

• Evolution the theory that organisms change over
  time
• Natural Selection Charles Darwins idea that
  organisms with the best traits will live to
  reproduce and pass on their genetic information
• Adaptation a trait that enables an organism to
  survive in the wild

3
Fossils

• Fossils are remains or traces of dead organisms
  buried and preserved in sedimentary rock.
• Fossils present a vivid record of the earliest
  life on Earth and of a progression over time
  from simple to more-complex life forms.

4
Scientists have learned about prehistoric life by
studying fossils of ancient insects such as this
midge fly It was trapped in tree resin when it
was alive. The resin eventually hardens and
fossilizes into amber. Sometimes an entire
organisms is preserved in this manner.
5
Although trilobites became extinct over 200
million years ago they left detailed casts in
the rocks where they died. This silica shale
formation shows several trilobites. Because these
primitive arthropods were typical organisms of
the Paleozoic era a paleontologist may use them
to determine the relative age of the rock strata.
6
This fossil cast shows the remains of
Archaeopteryx a birdlike dinosaur. It had teeth
and a long reptile-like tail covered with
feathers. Archaeopteryx lived between 163 million
and 144 million years ago.
7
Distribution of Species

• How different species of plants and animals are
  geographically distributed in nature and how
  they relate to their environment and to each
  other is evidence of change over time.
• Populations that exist on islands provide living
  clues of patterns of evolution.

8
Darwin first observed the adaptive radiation of
the Galapagos finches. Finches living on
different islands changed over long periods of
time due to the different habitats or living
conditions.
9
The distribution of the worlds flightless birds
reflects the shifting of continents (Plate
Tectonics). These birds supposedly shifted with
the continents too. Following this separation
the flightless birds of each of these new
continents gradually evolved into one or more
distinct speciesthe ostrich of Africa (shown
here) the rhea of South America and the
cassowary and emu of Australia.
10
Anatomical Similarities

• The study of the internal and external features
  of different living things is known as
  comparative anatomy.
• It provides a wealth of information about
  evolution.

11
Structures that are similar due to evolutionary
origin such as the forearm bones of humans
birds porpoises and elephants are called
homologous structures.
12
All vertebrate brains share the same basic
three-part structure the cerebrum the
cerebellum and the brain stem. Their size and
development varies. In mammals the cerebrum
dominates the brain. It is most developed among
primates in whom cognitive ability is the
highest.
13
Vestigial Structures

• Some organisms have structures or organs that
  seem to serve no useful function. These are
  called vestigial organs or structures.
• Human tailbone appendix body hair
• Male nipples in mammals
• Some snakes and whales tiny pelvic bones and
  limb bones
• Some cave-dwelling salamanders have eyes even
  though members of the species are completely
  blind.
• Vestigial organs are often homologous to organs
  that are useful in other species.

14
Embryology

• Comparison of the vertebrate development before
  birth.
• Gill pouches in both the bird embryo and the
  human embryo.
• A flexible notochord develops in the back.
• Blocks of tissue called will become muscle
  vertebrae connective tissue and later the
  larger glands of the body.
• Helps biologists identify like structures that
  are less apparent in adults.

15
DNA Amino Acid Chain Comparison

• DNAs uniformity organisms have the same
  building blocks base pairing A w/T C w/ G.
• Different combinations of these bases direct the
  assembly of amino acids into functional proteins.
  
• DNA is thought to be a record of an organisms
  evolutionary history. Scientists gain insights
  into how different species are related by
  comparing the same proteins from different
  species.
• In closely related species the proteins vary by
  only one to a few amino acids.
• More distantly related organisms generally have
  proteins with fewer similarities.