Bones are light because they are hollow inside and filled primarily with marrow, a spongy substance which produces new red blood cells in large bones.
The type of muscles that wrap around bones are typically skeletal muscles, but muscles do not make the bones light. What makes bones light are the fact that they are porous. There are a lot of holes within the bones that make it lighter, but those holes make sort of arcs and what not, similar to those in the Eiffel tower, for example. They are light weight, but very strong.
The answer is bones. Bones are filled with marrow and have air spaces to make them lighter in weight.
Birds
They have hollow bones,only one ovary present
The bones are hollow and make the bird light and he can fly by flapping his wings.
Most bird bones are very light, because extra weight would make it impossible to fly.
Bones are light because they are hollow in the middle.
Birds have hollow bones to help them fly. Solid bones would add to much weight and make it impossible to fly. They have crisscross structures to add support inside the bones.
Hollow bones, curved wings to make them aerodynamic and light feathers to make them almost weightless.
they have hollow bones because they need to be light
Birds have hollow bones that make them lighter so they can fly more easily.
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