Model It!
What? No Bones?
Figure 4 Most of the known animals on
Earth are invertebrates. These organisms
lack the backbone found in humans,
birds, reptiles, and other vertebrates.
Develop Models Choose a kind of
invertebrate-snail, insect, worm, octopus,
water bear (shown here), and spider are just
a few. Consider how an animal maintains
its structure with no bones. Then sketch a
diagram to explain how your animal moves
with no bones connected to its muscles.