Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A small zoo has fishes in its aquarium, frogs, tortoises, crocodiles, pigeons and deer. How many heart chambers do all the animals have together? How many of them have four-chambered hearts, and how many are warm-blooded?
Fishes have 2 heart chambers, amphibians 3, most reptiles 3 (crocodiles 4), birds and mammals 4. Only birds and mammals are warm-blooded. Reptiles have dry skin with scales; birds have feathers, pneumatic bones and air sacs; mammals have hair, pinnae and mammary glands, and most are viviparous, but Ornithorhynchus lays eggs.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Chambers. .
Step 2. Four-chambered hearts. The crocodiles, pigeons and deer: .
Step 3. Warm-blooded. Only the pigeons and the deer: . The crocodiles have four chambers but are cold-blooded.
Answer: chambers in all; four-chambered hearts; warm-blooded animals.
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