On a forest trail, Rocket spots a round bundle of spiky fur high in a tree. "Is that a pinecone with a face?"
Raven laughs softly. "It is a porcupine! It climbed up to munch on bark."
A box turtle crosses the path below. Its domed shell bumps slowly over the twigs.
"Two animals, two ways to stay safe," Raven says. "What do you notice they have in common?"
Nova hovers back to give them space. "My hint," she says. "Look at what is on the outside of each one."
A porcupine is covered in about 30,000 quills. The quills come off easily when another animal touches them.
Porcupines do not throw or shoot their quills. That is a myth.
A turtle's shell is made from fused ribs and backbone. The shell helps protect it from other animals.
Your heart is a muscle about the size of your fist. It pumps all day to move oxygen around your body.
Your lungs take in oxygen from the air you breathe. They breathe out a waste gas called carbon dioxide.
Your stomach muscles mix food with digestive juices. Your body needs the nutrients from food to grow and work.
Your brain gets messages from your senses and tells your muscles how to move.
| Structure | Inside or outside? | Function |
|---|---|---|
| Porcupine quills | outside | protection |
| Turtle shell | outside | protection |
| Heart | inside | pumps to move oxygen around the body |
| Lungs | inside | take in oxygen |
| Stomach | inside | mixes food with digestive juices |
Porcupines and turtles both protect themselves, but in different ways.
A porcupine's quills come off easily when another animal touches them.
A turtle's shell is part of its skeleton. It helps protect the turtle.
| Statement | True or false? |
|---|---|
| Porcupines can climb trees. | ? |
| Porcupines shoot their quills like arrows. | ? |
| Your brain tells your muscles how to move. | ? |
| Your stomach mixes food with digestive juices. | ? |
You explored animals inside and out! Tomorrow you make a scientific argument about a structure.