Metamorphosis
Metamorphosis is when an animal completely changes its body shape as it grows up.
A small lump of bread dough sits in a bowl. You cover it with a cloth and leave it on the counter. Hours later, you lift the cloth and find a large, airy dome that looks nothing like before. The same dough went through a set of inner changes and came out as a new form.
Explaining metamorphosis by grade level
A caterpillar wraps itself in a shell and comes out as a butterfly. Its whole body changes shape inside that shell. Warmer air can make this change happen faster. Cooler air makes it take more time.
Projects that explore metamorphosis
The body-shape change that happens inside the pupal case follows its own internal program. Tiger swallowtail pupae were split into three groups: one got one minute of UV light each day, another got five minutes, and a third received none. After the adults hatched, each butterfly was measured for wing span, body length, and percentage of black on the wings. Neither one minute nor five minutes of UV exposure produced any significant difference between groups.
Temperature controls how fast a caterpillar completes its transformation. Painted Lady caterpillars were raised in three groups at 18°C, 24°C, and 30°C — each group of twenty in a transparent tank with a leafy plant. The chrysalis (hard shell) stage was observed each day, and the group at 30°C finished the change fastest. As a result, the group at 18°C took the longest to emerge as butterflies.