The History Of The Tortoise Reading Passage
The History Of The Tortoise Reading Passage
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If you go far back, everything lives in the ocean. At different topics in evolutionary history, interested individuals from different animal groups travelled to land, sometimes taking their own seawater in blood and cellular fluids, even to the aridest deserts. In addition to the reptiles, birds, mammals, and insects that surround us, other groups that have conquered the water contain scorpions, snails, and crustaceans such as woodlice, land crabs, millipedes and centipedes, spiders, and different worms. We must not forget the vegetation, without whose pre-invaded land, no other migrations could have taken place.
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Going from water to land involves a significant reshaping of every part of life, as well as respiration and reproduction. However, a good number of terrestrial animals later returned, abandoning the hard-earned terrain resurfacing tool and returning to the water. The seals were only partially returned. On the way to extreme events like Whales and dugongs, they display to us what mediators would have been like. Whales and dugongs, their closest relatives, the Manatees, ceased to be terrestrial creatures as a whole and returned to the whole marine customs of distant ancestors. They do not even come ashore to breed. Nevertheless, they still breathe air, creating nothing similar to the gills of their previous marine incarnation. Turtles went to sea a long time ago, and like all vertebrates that return to the water, they breathe air. Yet, they are, in a way, less likely to return to the water than whales or dugongs because turtles still lay their eggs on the beaches.
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There is proof that all modern turtles are descended from a terrestrial ancestor who lived before most dinosaurs. From the earliest dinosaur times, there are two major fossils known as Proganochelys quenstedti and Palaeochersis talampayensis, all of which are closely related to the ancestry of modern turtles and tortoises. You may be wondering how we can tell if fossil animals lived on land or in water, particularly when only fragments are discovered. Sometimes it’s clear. Ichthyosaurs are reptile contemporaries of dinosaurs, with paddles and streamlined bodies. The fossils look like dolphins, and they certainly lived in the water like dolphins. With turtles, it manifests a little less. One method is to measure the bones of their forearms.
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Walter Joyce and Jacques Gauthier of Yale University obtained three measurements on the specific bones of 71 species of living turtles and turtles. They used a type of triangular graph paper to plan all three measurements against each other. All terrestrial turtle species formed a tight spot at the top of the triangle, while all water turtles are at the bottom of the triangular graph. They are not mutually exclusive, except for some species that spend time in water and land. Of course, this amphibious species appears on the triangular graph almost halfway between the 'wet cluster' of sea turtles and the 'dry cluster' of land turtles. Determining where the fossils fell was the next step. We have no doubt the bones of P quenstedti and JR talampayensis. Their points on the graph are the thickness of the dry mass. Both of these fossils are arid land turtles. They came before our turtles could return to the water.
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So, as most mammals did after going to sea, you might guess that modern land turtles may have stayed on land since that early terrestrial period. But obviously not. If you draw the family tree of all current turtles and tortoises, almost all the branches are aquatic. Today's land turtles are a branch with deep nests built among the branches of aquatic turtles. This suggests that modern land turtles have not relied on the land continuously since the time of P. quenstedti and P. talampayensis. On the contrary, their ancestors were among those who returned to the water, and they reappeared on land in recent times.
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Therefore, turtles represent significant double returns. As with all mammals, reptiles, and birds in general, their distant ancestors were marine fish, before which various more or less worm-like creatures still in the sea developed into primary bacteria. Later, ancestors lived on the land and stayed there for many ages. Afterwards, ancestors still turned into water and became sea turtles. Eventually, they returned to the land as turtles, some of which now live in arid deserts.
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