Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. The images below show embryos of different species at different stages of
development. Label the images below with 1-4 from least developed to most
developed.
A 4 B 1 C 3 D 2
2. Which image above do you think is a human? Explain. Because it looks like the
embryo of a human at every early stage
Gizmo Warm-up
Embryology is the study of the development of embryos
from a single cell to a multicellular fetus. In the Embryo
Development Gizmo, you will compare the development of
different animals and learn the details of mammalian
development. To begin, be sure the COMPARE tab is
selected.
1. What do the images have in common? They are all single celled
2. Click on the check box to turn on Scale bars and labels. You are observing the
zygotes, or fertilized single cells, of five animals.
At this point, are you able to tell which animal is which? no Explain. They are not
developed enough to be able to tell. One would be able to tell once distinguishing
features begin to appear but so far there is only a base for each of the embryos.
, Get the Gizmo ready:
Activity A:
• Make sure the COMPARE tab is selected and
Comparative
embryology the
Developmental stage slider is on stage 1.
• Turn off Scale bars and labels.
Introduction: Comparative embryology compares embryos of different species to
gain insight into how they are related. To provide a framework for this comparison,
embryologists divide this process into 23 Carnegie stages. You will look at seven of
these stages in this activity.
Question: Can we use comparative embryology to determine the relatedness of species?
1. Challenge: Drag the labels to the embryos you think they belong to. Fill in the
first row of the table below with your guesses. Then, move the Developmental
stage slider one position to the right, to Carnegie stage 4. Rearrange your labels
if necessary and fill in the next row of the table. Continue until you get to stage
23. Don’t turn on the Reveal answers check box until the end. (Note: Your
guesses may change as you go through the stages. Don’t worry, they won’t be
graded - this is just for fun!)
Stage A B C D E
1 Mouse Human Frog Fish Chicke
n
4 Huma Mouse Frog Chicke Fish
n n
8 Frog Human Frog Chicke Fish
n
13 Frog Human Frog Mouse Fish
16 Frog Human Mous Chicke Fish
e n
20 Frog Chicke Mous Human Fish
n e
23 Frog Chicke Mous Human Fish
n e
2. Reveal: Click Reveal answers.
A. Did you guess correctly in the end? Yes
B. At which stage were you able to tell which was which? 20
Explain: All the main features of each animal had already developed by this
point
3. Observe: Drag the Developmental stage slider back to stage 8. Turn on Scale
bars and labels. What structure does all of the embryos have in common?
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