Transcript Evidence of Evolution

EVIDENCE OF EVOLUTION
Write the underlined
information into your notes.
EVIDENCE #1:
COMPARING ANATOMY
• Question: What do homologous structures
suggest about the process of evolutionary
change?
COMPARING ANATOMY
• Answer: Evolutionary theory explains the
existence of homologous structures
adapted to different purposes as the result
of descent with modification from a
common ancestor.
COMPARING ANATOMY
• Homologous structures: similar structures
that are shared by related species and that
have been inherited from a common
ancestor.
• Limbs of frogs, alligator, chicken and
horse have similar bones structure but
different functions.
HOMOLOGOUS
STRUCTURES
COMPARING ANATOMY
• Similarities and differences among
homologous structures help determine how
recently species shared a common
ancestor.
• For example, many bones of reptiles and birds
are more similar to one another in structure and
development than they are to similar bones of
mammals.
• So birds are more closely related to crocodiles
(reptile) than they are to bats (mammal)!
COMPARING ANATOMY
• Analogous structures: body parts of
organisms that share common
functions, but not common structure
and development.
• Wing of a bee vs. wing of a bird.
COMPARING ANATOMY
• Vestigial structures: inherited from
ancestors but have lost much of their
original size and function due to
different selection pressures acting on
the descendant.
• Hipbones in dolphins
THINK ABOUT IT…
• Why do organisms retain structures that are
just vestiges, or traces, of the original? One
possibility is that the presence of the
structure does not affect an organism’s
fitness, and therefore, natural selection
does not act to eliminate it.
LETS BUILD A
CLADOGRAM
• Take a look at the pictures of the 7 cats.
• How would you group them on a cladogram based on
appearances?
• Gallery Walk and see how other’s grouped the cats.
• There is no right or wrong answer here; as long as you
base your choices on specific anatomy of the cats.
EVIDENCE #2:
BIOGEOGRAPHY
• Question: How does the
geographic distribution
of species today relate
to their evolutionary
history?
BIOGEOGRAPHY
• Answer: Patterns in the distribution of living
and fossil species, combined with
information from geology, tell us how
modern organisms evolved from their
ancestors.
CLOSELY RELATED BUT
DIFFERENT
• To Darwin, the biogeography of
Galapagos species suggested
that populations of several bird
species on the islands had
evolved from mainland species.
Over time, natural selection on
different islands selected among
individuals with different inherited
variations. That caused
populations on different idlands
to evolve into different, but
closely related species.
DISTANTLY RELATED BUT
SIMILAR
• In contrast, Darwin noted that similar
ground-dwelling grassland birds in Europe,
Australia, and Africa were not closely
related, but looked similar. Differences in
basic body structures among those birds
provide evidence that they evolved from
different ancestors. But natural selection in
similar habitats caused distantly related
species to develop similar adaptations—
such as long legs and feet with toes
adapted to running.
BIOGEOGRAPHY
• Closely related species evolve diverse
adaptations in slightly different
environments.
• Very distantly related species develop
similar adaptations in similar environments.
LETS EXPLORE…
• Examine the present day locations of 7 big cats.
• Read “A lesson in paleogeography”
• Revise your ‘rough draft’ cladogram using the
information provided.
• Gallery walk and examine all the possible
cladograms students created using the same
information.
THINK ABOUT IT…
• How is the gallery walk you did in class like
peer review for evolutionary biologists?
• Why is this an important step for the
biologist?
EVIDENCE #3: FOSSILS
• Question: How do fossils help to document
the descent of modern species from
ancient ancestors?
FOSSILS
• Answer: Many recently discovered fossils
form series that trace the evolution of
modern species from extinct ancestors.
FOSSILS
• Evolution takes a long time. If life
has evolved, then Earth must be
very old. Geologists use
radioactivity to establish the age
of rocks and fossils. Radioactive
dating indicates that Earth is
approximately 4.5 Bya (Billion
years old)!
FOSSILS
• Paleontologists have
discovered 100’s of
kinds of fossils that
document
intermediate stages
in the evolution of
many different
groups of modern
species.
FOSSILS OF DORUDON: AN EXTINCT
INTERMEDIATE BETWEEN TERRESTRIAL AND
AQUATIC MAMMALS.
• Notice the bones near the tail that appear to
be ‘floating’. These are the evolutionary
leftover leg bones from the terrestrial ancestor
of this aquatic Dorudon organism.
LETS TAKE A CLOSER
LOOK…
Examine the organisms on your table.
• The black part of the pictures represent bones
and/or fossils.
• The grey part of the pictures represent the size of
the organism.
• The skeletons are all made to be the same size
for your comparison; but these organisms
ranged from the size of a mouse to the size of
modern day whale as you can see from the
grey outlines.
READY, SET, GO!
• Arrange the organisms from ancient to
most recent.
• Use the bones/fossils to help you determine
the order of the pictures.
• Gallery walk and observe how other groups
created their timeline or “cladograms”.
• Now, check your cladogram against a
similar one in your book on pages 466-7.
THINK ABOUT IT…
• Suppose that you worked with several
science teams around the world. You all
shared fossils, pictures and data to come
up with this cladogram as a group. It is the
current accepted theory of how terrestrial
mammals evolved into aquatic mammals.
• Can this theory change?
• If no, why not?
• If yes, what has to happen?
EVIDENCE #4: COMPARING
DEVELOPMENT
• Question: What do similarities in
development suggest about the process of
evolutionary change?
COMPARING
DEVELOPMENT
• Answer: Similar
patterns of
embryological
development
provide further
evidence that
organisms have
descended from
a common
ancestor.
COMPARING
DEVELOPMENT
• Researchers noticed a long time ago that
the early developmental stages of many
animals with backbones look very similar.
• Recent observations show groups of
embryonic cells develop in the same
order and in similar patterns to produce
many homologous tissues and organs.
COMPARING
DEVELOPMENT
ACTIVITY
• Can you distinguish between the turtle,
human, fish and salamandar at the first
stage of development?
• What about at the second stage?
• What about at the third?
STAGE 1
STAGE 2
STAGE 3
COMPARING
DEVELOPMENT
COMPARING
DEVELOPMENT
• Because these
organisms share a
common ancestor,
they all have similar
developmental
genes or DNA.
• They all begin
developing in much
the same way.
• Eventually though,
their DNA will begin
producing traits
unique to that
species.
EVIDENCE #5: GENETICS
• Question: How can molecular biology
(Biomolecule = nucleic acids) be used to
trace the process of evolution?
GENETICS
• Answer: At the
molecular level,
overwhelming
similarities in the
genetic code of all
organisms, along
with clearly
homologous
molecules, provide
evidence of
common descent.
GENETICS
• All living cells use information coded in DNA
and RNA to carry information from one
generation to the next.
• This genetic code is nearly identical in
almost all organisms, including bacteria,
fungi, plants and animals.
• This is powerful evidence that all
organisms evolved form common
ancestors that shared this code.
GENETICS ACTIVITY #1
• Grab a text book, a scrap piece of paper
and a calculator!
• Turn to page 470.
• In the “Analyzing Data” section, do #1-4
and write your answers on your paper.
• Show your work for #1 and 2!
• Write in complete sentences for #3 and
4.
GENETICS ACTIVITY #2
• http://www.hhmi.org/biointeractive/creatingphylogenetic-trees-dna-sequences
GENETICS ACTIVITY #3
• Obtain homologous pieces of DNA of the 7
big cats.
• How do they compare?
• Which cats seem to be closely related?
(very few differences)
• Which cats seem to be distantly related?
(Many differences)
• Which cats are intermediates?
• Revise your cat cladogram now that you
have new evidence.
• Gallery walk and see how other groups
made their cladograms.