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Odyssey of Life, Part I—The Ultimate Journey
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Classroom Activity
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Objective
To put in correct order the developmental stages for a fish, chick,
pig, calf, and human.
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copy of "Timing Is Everything" student handout (PDF
or
HTML)
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Copy and distribute the "Timing Is Everything" student handout.
Have students cut out and reassemble the squares in an order
that correctly represents three developmental stages of the five
animals depicted (fish, chick, pig, calf and human).
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When students finish, have them explain the reasoning behind
their answers. To conclude, have a discussion about the
similarities and differences students see in the embryos. Since
these five animals look similar in their early embryonic stages,
might all vertebrates look similar in those stages? What might
that suggest?
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As an extension, have students research how the theory of
evolution has been viewed from the 1800s through today.
stage 1: 8, 2, 4, 10, 3
stage 2: 1, 7, 15, 6, 11
stage 3: 14, 9, 13, 12, 5
Students may think that the embryos only look similar. Point out
that the backbones and limbs of all four-limbed vertebrates (also
called tetrapods) are identical in embryonic origin and underlying
structure. Even though they may differ in final external form and
function, the various tetrapod limbs (arms, legs, flippers, wings)
are all built from precisely the same sets of embryonic tissues, are
supported by the same sets of bones, and are moved by the same sets
of muscles. These extensive homologies reinforce the scientific
understanding that all tetrapods have descended, with various
modifications, from ancient, long-extinct ancestors.
Note: These illustrations are representations—not exact
depictions—of the embryonic stages of each of these five
animals.
Book
Lewin, Roger. The Origin of Modern Humans. New York:
Scientific American Library: Distributed by W.H. Freeman, 1993.
Looks at possible preludes to Homo sapiens, various hypotheses
regarding the origin of modern humans, the idea of a Mitrochondrial
Eve, the archeology of modern humans and the origin of language.
Web Sites
NOVA Online—Odyssey of Life
http://www.pbs.org/nova/odyssey/
Includes a cyberdebate about how humans evolved; time-lapse
sequences of growing human, pig, chicken and fish embryos; an
interview with photographer Lennart Nilsson; an essay about the
commonalities among species; and an online activity that reveals
what bugs live in, on and around us.
Talk Origins
http://www.talkorigins.org/
This newsgroup is devoted to the discussion and debate of biological
and physical origins. Most discussions in the newsgroup center on
the creation-evolution controversy, but other topics of discussion
include the origin of life, geology, biology, cosmology and
theology.
The Visible Embryo
http://www.visembryo.com/
Follows human embryological development over 40 weeks, providing
in-depth information about what occurs at each stage. Requires
Shockwave or QuickTime plug-ins.
The "Timing is everything" activity aligns with the following
National Science Education Standards:
Grades 5-8
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Science Standard C:
Life Science
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Structure and function in living systems
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Specialized cells perform specialized functions in multicellular
organisms. Groups of specialized cells cooperate to form a
tissue, such as a muscle. Different tissues are, in turn,
grouped together to form larger functional units, called organs.
Each type of cell, tissue and organ has a distinct structure and
set of functions that serve the organism as a whole.
Grades 9-12
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Science Standard C:
Life Science
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The cell
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Cells can differentiate, and complex multicellular organisms are
formed as a highly organized arrangement of differentiated
cells. In the development of these multicellular organisms, the
progeny from a single cell form an embryo in which the cells
multiply and differentiate to form the many specialized cells,
tissues and organs that comprise the final organism. The
differentiation is regulated through the expression of different
genes.
Biological evolution
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The great diversity of organisms is the result of more than 3.5
billion years of evolution that has filled every available niche
with life forms.
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The millions of different species of plants, animals and
microorganisms that live on Earth today are related by descent
from common ancestors.
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