Transcript Activity 99 Power Point

Challenge How are modern and
fossil skeletons used to investigate
evolution?
KeyVocabulary:
Fossil Record
Natural Selection
Getting Started…
 Are whales mammals or fish?
 How do you think whales evolved: do you
think some mammals evolved from land to
sea or that a type of fish evolved to have
mammalian traits?
 What type of evidence could help you
answer this question?
Doing the Activity:
1. Read “The Fossil Exhibit” on page 49
2. Follow the procedure on pages 49-50.

Make sure you copy the data table into your notebooks
in step #1
Comparing Skeletons
Similarities
Group 1 Skeletons:
__A, M____________
Group 2 Skeletons :
__B, D, O________
Group 1 skeletons
compared with
Group 2 skeletons.
Differences
What can be inferred about the evolution of
whales based on the physical
characteristics?
 How can we decide which was the ancestor of modern
whales, Skeleton D or Skeleton B?
Evolution of
whales has
involved the
extinction of
some groups
and the
formation of
others by
branching speciation
How are whales and cows related
then??
The
evolution of
aquatic traits
in this
lineage of
mammals
took about
20 million
years
Whales and cows share a
common ancestor known as
paraxonions. It is similar to
a cousin relationship!
Is there a trend in this
evolutionary tree toward
evolving to live in water?
Not only whales evolved
from the common
ancestors on this
evolutionary tree, but also
cows, sheep, pigs, and
hippopotamuses
Analysis #1a
 Skeletal changes in the evolution of whales”
 External hind limbs are lost and the bones either greatly
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reduced or lost entirely;
The skull changes size and shape
Forelimbs turn into fins
Tail elongates due to loss of the pelvis and external hind
limbs
The tail vertebrae become thicker and larger
The enlarged neck vertebrae shrink (indicating reduced
need)
Analysis #1b
Inferences about changes in habitat because of skeletal
changes:
 These skeletal changes indicate a transition from
predominantly land-dwelling animals to ones that
lived partly in shallow water, and eventually to animals
with an exclusively aquatic habitat.
Analysis #3
 Comparing skeletons can show similarities and
differences among species.
The numbers of these similarities and differences
allow scientists to infer relationships among different
animals/groups of organisms
If you have enough fossils, an evolutionary tree can be
made.
Analysis #5
 Student answers will vary with their opinions
Homework
Analysis Question # 2
 Use Natural Selection to describe
how/why ONE of these changes
occurred.
Changes:
 Teeth, Rib Cage, Length, Limbs,
Vertebrate, Skull shape/size etc.