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May 10, 2017 Aims:
SWBAT analyze and evaluate the scientific evidence provided
by the fossil record.
Agenda
1. Do Now
2. Class Notes
3. Guided Practice
4. Independent Practice
5. Practicing our AIMS:
E.3-Examining Evidence
How will you help our class earn all of our S.T.R.I.V.E. Points?
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Aim Check:
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OBJECTIVES: By the end of class, students will be able to…
SWBAT analyze and evaluate the scient ific evidence provided by the fossil record.
DO NOW 1. The diagram below shows a population of adult giraffes over time. Letters A, B, and C represent
three time periods. Use Darwin’s theory to explain what has occurred over the generations.
2. Brainstorm how the fossil record could be used as evidence to support the theory of evolution.
SCIENCE 8
Examining
Ev idence
E.3
Name: _____________________________
Date: ________________________________
Homeroom: _________________________
Evolution
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CLASS NOTES
EVOLUTIONARY EVIDENCE EVIDENCE #1: COMPARATIVE ANATOMY
What it is
COMPARATIVE ANATOMY:
_________________________________________________________________
_________________________________________________________________
What it means
Whales: Mammals or Fish?
Part icular
details
HOMOLOGOUS STRCUTURES:
_________________________________________________________________
_________________________________________________________________
o Whales, bats, hippos, and people all have the same bones in their
front appendages
EVIDENCE #2: EMBRYOLOGY
What it is
EMBRYOLOGY:
_________________________________________________________________
_________________________________________________________________
What it means
Dolphins vs Humans
Part icular
details
Studying the embryological development of liv ing things provides clues to
the evolution of present-day organisms.
During some stages of development, organisms exhibit ancestral features in
whole or incomplete form.
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EVIDENCE #3: FOSSIL RECORD
What it is
FOSSIL RECORD:
_________________________________________________________________
_________________________________________________________________
What it means
No legs or 4 legs?
Part icular
details
TRANSITIONAL FORMS:
_________________________________________________________________
_________________________________________________________________
EVIDENCE #4: DNA
What it is
DNA:
_________________________________________________________________
_________________________________________________________________
What it means
Common Ancestor?
Part icular
details
COMMON ANCESTOR:
_________________________________________________________________
_________________________________________________________________
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INDEPENDENT PRACTICE
Directions: Summarize what you learned today in the space below. You may use
words, pictures, charts, or a combination of these.
Focus on the following for your summary:
What ev idence do scientists use to determine common ancestors among species?
Explain how each type of ev idence is used to demonstrate evolution.
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Case study: Land-living ancestors of whales Fossils offer crucial clues for evolution, because they reveal the often remarkable forms of creatures long
vanished from Earth. Some of them even document evolution in action, recording creatures moving
from one environment to another.
Whales, for example, are beautifully adapted to life in water, and have been for millions of years. But,
like us, they are mammals. They breathe air, and give birth to and nurse live young. Yet there is good
evidence that mammals originally evolved on land. If that is so, then the ancestors of whales must have
transitioned to the water at some point.
As it happens, we have numerous fossils
from the first ten million years or so of
whale evolution. These include several
fossils of aquatic creatures such as
Ambulocetus and Pakicetus, which have
characteristics now seen only in whales —
especially in their ear anatomy — but also
have limbs like those of the land-living
mammals from which they are clearly
derived.
In 2007, scientists identified a possible link
between land mammals and whales.
Called raoellids, these now-extinct
creatures would have looked like very
small dogs, but were more closely related
to hooved animals — the group that
includes modern-day cows, sheep, deer,
pigs and hippos. Scientists found that
molecular evidence also suggests a deep
evolutionary connection between whales
and these hooved animals. One raoellid,
Indohyus, is similar to whales but has some
differences (ears, teeth, bone thickness)
from hooved animals. These indicators
suggest that this raccoon-sized creature
spent much of its time in water. Therefore,
Indohyus could be the transition organism
between land and sea.
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1. What is the claim being made in the text and what evidence supports this claim?
2. Interpret the fossil record shown in the case study, which indicates the evolution of the modern
whale. Note at least two specific changes in the structure/characteristics over time.
3. The passage states that molecular evidence was used to support the connection between whales
and hooved animals. Identify the type of molecular evidence we have learned about that can be
used to indicate relationships.
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The forelimbs below all have a similar structure (A), yet each
one is found in a different species (Bird, bat, cat, whale, and
human).
These structures are known as HOMOLOGOUS STRUCTURES, or
body parts with similar structures found in different species.
The word homologous, coined in about 1656, derives from the
Greek homologos, where homo = same and logos =
relationship. Homologous structures can indicate evolutionary
relationships between organisms.
4. Scientists use both the fossil record and homologous
structures as evidence that evolution occurs. Fossils are
remnants of skeletons from ancient organisms that are
preserved underground. When a scientist examines
homologous structures they might also look at bones, but
how are homologous structures DIFFERENT from fossils?
5. What does it mean if species are said to have “common ancestors”?
6. Take a closer look at the bone from the whale. Notice that whales, like humans, have five finger like
structures inside their fin. How does this homologous structure help support the theory of evolution?
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Acanthostega, an
early tetrapod
HIGH SCHOOL CHALLENGE
From Water to Land: Our Finned Ancestors The animals we are most familiar with are tetrapods — they are vertebrates (they have
backbones), four limbs, and they live on land. That includes humans, almost all domestic
animals and most of the wild ones that any child would recognize: mammals, birds,
amphibians and reptiles. The vast majority of vertebrates, however, are not tetrapods, but fish.
There are more kinds of fish, in fact, than all the species of tetrapods combined. Evolutionary
Biologists believe that all life actually began in the sea. Indeed, through the lens of evolution,
tetrapods (humans and most other animals) are just one branch of the fish family tree! In other
words, tetrapods are the relatives of fish but happen to be adapted for life out of water.
The first transition from water to land took place more than 360 million years ago. I t was one of
the most demanding such moves ever made in the history of life. How did fins become legs?
And how did the transitional creatures deal with the demands of land life, from the dry
environment to the weight of gravity?
I t used to be thought that the first land creatures were stranded fish that
evolved to spend more and more time ashore, returning to water only to
reproduce. Over the past 20 years, palaeontologists have uncovered fossils
that have turned this idea upside down. The earliest tetrapods, such as
Acanthostega from around 365 million years ago, had fully formed legs, with
toes, but retained internal gills. These gills would have soon dried out if this creature was on
land for a prolonged period of time. This lead scientists to believe that fish evolved legs long
before they came on land! The earliest tetrapods did most of their evolving in the more
forgiv ing aquatic environment. Coming ashore seems to have been the very last stage of their
evolution.
Researchers suspect that all tetrapods evolved from creatures called elpistostegids. These very
large, carnivorous, shallow-water fish would have looked and behaved much like alligators, or
giant salamanders. They looked like tetrapods in many respects, except that they still had fins.
Until recently, elpistostegids were known only from small fragments of fossils that were poorly
preserved, so it has been hard to get a rounded picture of what they were like. In the past
couple of years, several discoveries from northern Canada have changed all that. In 2006,
Edward Daeschler and his colleagues described spectacularly well- preserved fossils of an
elpistostegid known as Tiktaalik. This new fossil allow us to build up a good picture of an
aquatic predator with distinct similarities to tetrapods — from its flexible neck, to its very limb-
like fin structure.
Elpistostegid: This is a computer rending that
scientists were able to produce from the Tktaalik
fossil of an Elpistostegid
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1. What is a tetrapod in your own words? Also provide an example of a tetrapod that is not mentioned
in the text.
2. How did scientists’ theory about the evolution of tetrapods change with the finding of the
Acanthostega fossil? What evidence did they find that refuted their initial hypothesis?
3. Tetrapods such as humans, cows, and lizards are all extremely different organisms. However,
according to the fossil record all they share a common ancestor . In other words, all tetrapods evolved
from the same ancient organism. What is the common ancestor of humans, cows, and lizards
according to the text?
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Science 8
E.3:
Examining Evidence
Name: _____________________________
Date: _______________________________
Homeroom: _________________________
Quick Notes:
SKILL SNAPSHOT
Like A Scholar?
Yes No
Redo?
Yes No
1. Scientists call the fossil pictured a “transitional fossil” because it has characteristics of both dinosaurs
and birds. How does this fossil serve as evidence for the theory of evolution?
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Directions: Answer each multiple choice question. Once you have selected the best answer, justify your reasoning
in the text box.
Your justification needs to be in complete sentences and use ev idence from today’s packet.
2. Several species of extinct giant tortoise lived on different islands in the Indian Ocean. One species is
still alive on Aldabra Island. The shells and skins of the extinct tortoises are in museums and can be
studied.
What is the most accurate way to find out how closely related the living one is to the extinct one?
A. Search the history records of what the extinct tortoises look like.
B. Compare the bones and shells of the extinct tortoises to each other.
C. Measure the distance between Aldabra and the other islands.
D. Compare the DNA of all the tortoise species, extinct and living.
3. Fossils of the Coelacanth fish occur in the fossil record from 410 to 65 million years ago. The lack of
more recent fossils led scientist to conclude that the fish went extinct along with the dinosaurs. In
1983, a fisherman caught a living Coelacanth.
More than 200 of them have been caught on the deep reefs in the Indian Ocean. This fish has been
called a “living fossil” because its body plans in nearly identical to the 400 million year old fossils.
This structural similarity supports which statement?
A. The environment of the deep sea has changed little over millions of years.
B. The amount of salt in the deep sea has varied greatly over millions of years.
C. The oceans have completely dried up multiple t imes during the past 400 million years.
D. The oceans have been continuously repopulated by freshwater fish species over millions of
years.