PACE WORK FORM 7 27/05/20

Тема: Динозаври. Походження та еволюція. Походження динозаврів.

1. Reading

Pre- reading task

 The theme of our today's lesson is Dinosaurs.

Reading

Paths of Dinosaur Evolution

Dinosaurs didn't spring suddenly into existence two hundred million years ago, huge, toothy, and hungry for grub. Like all living things, they evolved, slowly and gradually, from previously existing creatures--in this case, a family of primitive reptiles known as the archosaurs ("ruling lizards").

On the face of it, archosaurs weren't all that different from dinosaurs. However, these ancient reptiles were much smaller than most dinosaurs, and they had certain characteristic features (relatively splay-footed postures, for example) that set them apart from their more famous descendants. Paleontologists even believe they may have identified the single genus of archosaur from which all dinosaurs evolved: Lagosuchus ("rabbit crocodile"), a quick, tiny reptile that scurried across the forests of the early Triassic (and that also goes by the name Marasuchus).

This, unfortunately, is where we encounter one of those disagreements so common in paleontology. Scientists are unsure whether archosaurs coexisted with the therapsids (mammal-like reptiles) of the late Permian period (over 250 million years ago), or whether they appeared on the scene after the Permian/Triassic boundary, a geologic upheaveal that killed about three-quarters of all land-dwelling animals on earth. This would place the first archosaurs in the early Triassic period, a few million years later.

Also--and somewhat confusingly--it seems that later archosaurs (like Desmatosuchus ) coexisted with the earliest dinosaurs (like Eoraptor and Herrerasaurus ). In evolutionary terms, this poses no contradiction: evolved animals often wind up living side-by-side with the (relatively unevolved) descendants of their "progenitor" species. But it does pose a problem to paleontologists trying to definitively classify Triassic-period fossils.

Archosaurs weren't the only lizard-like creatures roaming the earth before the dinosaurs; there were also the therapsids, some of which looked like strange hybrids of mammals and reptiles. To show the strange twists and turns evolution can take, consider one of the most famous therapsids, Cynognathus ("dog jaw"). About the size of a large dog, Cynognathus may have been covered with fur, and it may also have given birth to live young instead of laying eggs. Most astonishingly, it seems likely that Cynognathus had a warm-blooded metabolism--anticipating the physiology of the first mammals that evolved from the therapsids during the late Triassic period.

The point of this story is that evolution isn't necessarily a linear process: the same adaptations can appear in widely separated epochs, depending on environmental conditions. Yes, we know that dinosaurs evolved from archosaurs, but play the tape of history over again and a whole different race of creatures might have evolved from a progenitor like Cynognathus. Dinosaurs might never have existed, and the first humans might have evolved way back in the Mesozoic Era rather than 60 million years later!

Finally, speaking of mammals, it's more than a little ironic that the dinosaurs owed their tens of millions of years of dominance to the Permian Extinction--because the dinosaurs themselves were wiped out by the K/T Extinction event 65 million years ago, which opened the door for the small, shrew-like mammals that survived to evolve (eventually) into the plus-sized megafauna mammals of the Cenozoic Era, and then into modern humans.

While-reading

T.: While reading the text, please make up a plot.

Post - reading task

2. Speaking

T.: Answer the questions:

1. Name the order of the evolutionary eras from earliest to latest.

2. What was the longest evolutionary era?

3. Name 2 characteristics of the evolution of fish to amphibians.

4. List the order of vertebrate evolution.

5. What 2 characteristics would amphibians have to change to

evolve into reptiles?

6. Why would there be no fossils found from before vertebrate evolution?

7. Name 4 characteristics of the evolution form reptiles to birds.

8. Name 2 characteristics for the evolution of reptiles to mammals.

Our lesson is coming to the end.

So, thank you for your hard work!  The lesson is over.

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