This key may seem confusing at first. Let's go through it, step by step. You'll find that it's not too hard.
1 Start at the top where it says animals . From here you have a choice - red blood or no red blood . Follow the straight lines to red blood .
Red blooded animals
You can see that the animals that have red blood are listed as mammals, lizards, birds and fish.
2 Now go back to the first choice of red blood or no red blood. This time choose no red blood .
Now you have another choice - hard bodies or soft bodies. Choose hard bodies .
Hard bodied animals with no red blood
From the key, you can see that animals that have no red blood and hard bodies are insects.
3 Go back to the choice between hard bodies or soft bodies . This time choose soft bodies. Now you have another choice, this time shell or no shell . If you choose shell , you've described shellfish.
Soft bodied animals with no red blood
Which animals have no red blood, soft bodies and no shell?
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