A Play in Two Acts
150 million years ago in the Age of Reptiles.
A grassy field next to a swamp next to a large lake. A large dinosaur is eating grass. He looks up and notices a small frog in the nearby swamp.
Scientific Narrator (SN): Both the dinosaur and the frog are vertebrates, that is, animals that have a backbone. A backbone is also known as a vertebral column, thus the name. The dinosaur is part of a group of vertebrate animals known as reptiles, and the frog is part of a group known as amphibians.
The frog plops from stone to stone in the swamp.
Dramatic Narrator (DN): All the world’s a stage, as the great bard William Shakespeare said, and on this great stage of life, which began with microscopic blobs and will end with…well, who knows… amphibians played a tremendously important role.
SN: Amphibians were the first animals to leave the water and live on land. Yet they cannot live fully as land animals because they lose too much water through their skin. They must constantly keep their skin moist. Also, their reproduction requires water.
DN: And so amphibians are forever tied to their watery origins.
The dinosaur stops eating grass and lumbers over to a clump of huge tree ferns with delicious leaves.
DN: All the world’s a stage, and on this great stage of life, which began with microscopic blobs…
SN: All right, already, get to the point!
DN: …reptiles also played a tremendously important role. Sheesh!
SN: Reptiles were the first animals able to spend their entire lives out of water. They became adapted to living on land; that is, they ever so slowly underwent changes that freed them from the constant need for water that amphibians required. Look at the dinosaur. He has a skin made of light, flexible scales that overlap and form a protective, almost watertight covering. These scales not only keep the skin from losing water, they also protect the dinosaur from getting hurt. This is one of the ways reptiles adapted to terrestrial life.
Next to a clump of huge tree ferns.
The dinosaur, a male, sees a female dinosaur on the far side of the ferns, and he approaches her.
DN: All the world’s a stage, and on this great stage of life…
DN: …reproduction takes place. You know, this isn’t just your play.
SN: Most of it is, since I wrote the script. So be quiet. Another way reptiles have adapted to terrestrial life is in their manner of reproduction. When it comes to reproduction, reptiles have overcome the need for water. In the actual act of reproducing, the sperm fertilizes the eggs internally. That is, the male places the sperm inside the female body...
DN: As the great bard William Shakespeare said, love is blind, and lovers cannot see…
SN: What does that have to do with anything?
DN: I don’t know, this is such an embarrassing topic.
SN: It’s life! Anyhow, with internal fertilization neither the sperm nor the eggs dry out. Thus we have a very clever solution to the problem. Now there’s also the problem of keeping the eggs that hold the newly created reptiles, that is, the embryos, from drying out. To avoid this, the females lay…
DN: Eggs. As the great bard William Shakespeare said (sort of), if this be magic, let it be an egg.
SN: No, not magic eggs, though in some ways they might seem magical. The shells of these eggs are tough enough to be watertight — so the embryos don’t dry out — yet porous enough to allow oxygen and carbon dioxide to pass in and out of the shell.
A long stretch of grassy plain with a clump of tree ferns in the distance.
The male dinosaur takes leave of the female and lumbers in the direction of the tree ferns.
DN: All the world’s a stage…
DN: …and reptiles are able to roam around it at will. If you don’t like my comments, I quit!
SN: Good riddance! Reptiles are far more active than amphibians, and that means they need more oxygen in their bodies. They meet this demand in several ways. The lungs of reptiles have small chambers, called alveoli if you’re of a scientific bent. These chambers increase the surface area. Also, muscles along the rib cage help move air into and out of lungs, and the heart is partially divided so oxygen-rich and oxygen-poor blood are separated. With all these changes, oxygen moves through the body more efficiently, and the ancient reptiles could grow big and strong.
DN: And did they ever!
DN: I’m going!
Noon in the desert.
A lizard is sunning itself on a rock.
SN: Metabolism refers to the different processes taking place within a living organism that are necessary for that organism to stay alive. The metabolism of a reptile is slow. In fact, it is so slow a reptile cannot make enough heat to warm its body, so it must absorb heat from its surroundings.
DN: Some people refer to reptiles as cold-blooded because of their slow metabolism, but the blood is not actually cold. This is a figure of speech, as when we say Macbeth’s wife, in the great bard William Shakespeare’s play of the same name, was cold-blooded. She really wasn’t, she was…
SN: I thought I told you to go!
DN: Maybe I don’t want to.
SN: THUS, the body temperature of reptiles is largely determined by the temperature of the world around them. Many reptiles regulate their temperature by basking in the sun to warm up or seeking shade to cool down. At very cold temperatures most reptiles become sluggish and unable to function.
Morning in the desert.
A wild cat sneaks up on and pounces upon a lizard sunning itself on a rock. The cat grabs the tail, but the lizard scurries way, leaving the cat with the tail.
SN: The tails of many lizards break off easily, allowing the lizard to escape. The lizard can then generate a new tail, but the new tail does not have any vertebrae in it.
DN: To paraphrase the great bard William Shakespeare, my tail, my tail, my body for a tail!
SN: What are you talking about?!
Evening in the desert.
A lizard stands completely still while a mosquito flits by. When the mosquito comes close to the lizard, the lizard snatches the mosquito.
DN: To paraphrase the great bard William Shakespeare again, out, out brief mosquito! Life’s but a walking shadow, a poor…
SN: Out, out, yourself! Get out of here!! Reptiles are important in the ecology of the global community because they are consumers: They eat large numbers of insect pests and small rodents.
The lizard gazes into the sunset.
SN: More than 6,000 species of reptiles are living today. Virtually all of them live on land. Today’s reptiles are remnants of a great number of species that inhabited Earth in ancient times.
DN: As the great bard William Shakespeare said, when to the sessions of sweet silent thought I summon up remembrance of things past, I sigh the lack of …
SN: A brain! You lack a brain! The reptiles of ancient times included dinosaurs, flying reptiles, and the like.
SN: I will never, ever produce another play with you as long as I live!
DN: As the great bard William… ouch!!!