An easy way to recall the differences between mammals, reptiles and amphibians is simple: You've got your "warm and fuzzies," your "cold and scalies" and your "cold and webbies." Of course, the distinct traits that separate each of these classes of animals are more nuanced than that, and require exploring the specifics.
The Warm and Fuzzies
The merit badges given only to mammals are as follows. Mammals:
- Are warm-blooded
- They have hair.
- They sport three middle ear bones.
- The females have mammary glands.
All of these traits belong to us as well, as we are human mammals. We also get to share the title of being a part of a class that includes the largest living animals on the planet; whales and elephants are also mammals. And except for two little oddballs -- the platypus and echidna -- we also give birth to live young.
Care for mammals as pets could be guided by considering how you might care for yourself. Comfortable temperatures, plenty of food and water, someplace soft to sleep and lots of attention probably would make your pet dog, cat, mouse or other mammal just as happy as it would make you.
Each class of animal -- and the species within them -- needs very specific care. Always talk to a veterinarian and educate yourself on your pet's needs before deciding which animal to own.
Cold and Scalies
In a class that boasts some of the most ancient-looking animals -- including crocodiles, turtles, lizards and snakes -- reptiles win a few awards of their own:
- They are cold-blooded.
- They have scales and teeth.
- Some have venom.
- They lay eggs.
They've also been around for a very long time; in comparison, mammals are practically newborns at this whole evolution thing. While we believe our class began between 144 million to 208 million years ago, reptiles made their earliest known grand entrance around 320 million years ago.
Reptiles aren't the easiest pet to own, and caring for them takes quite a bit of knowledge about the particular needs of each species. In general, these cold-blooded creatures will need access to a source of heat, a consistent feeding schedule and an enclosure with room to grow. Although not as into cuddles and affection as the mammals, reptiles can nevertheless make rewarding pets.
Cold and Webbies
Although in a tie with reptiles for the "cold-blooded" merit award, amphibians have plenty of unique characteristics as well:
- They live on both land and water.
- They have smooth, wet skin.
- They go through a metamorphosis.
- Their feet are webbed.
- They procreate by external fertilization.
Mammals give birth to live creatures that grow into an adult form, continuously. Reptiles are born looking exactly like tiny little versions of their adult selves. Amphibians, however, begin life as one thing: larvae or spawn, and then go through a rapid process as they change into their adult form. One trigger in all amphibians is responsible for this life-altering costume switch: a hormone known as "thyroxine."
Amphibian care is closer to that of reptiles instead of mammals, but because amphibians are creatures of both land and water, they will have some very important differences. The skin of amphibians is smooth and produces a slime from glands; dehydration causes serious harm and can be lethal.