If you go back far enough, everything lived in the sea. At various points in evolutionary history, enterprising individuals within many different animal groups moved out onto the land, sometimes even to the most parched deserts, taking their own private seawater with them in blood and cellular fluids. In addition to the reptiles, birds, mammals and insects which we see all around us, other groups that have succeeded out of water include scorpions, snails, crustaceans such as woodlice and land crabs, millipedes and centipedes, spiders and various worms. And we mustn’t forget the plants, without whose prior invasion of the land none of the other migrations could have happened.
Walter Joyce and Jacques Gauthier, at Yale University, obtained three measurements in these particular bones of 71 species of living turtles and tortoises. They used a kind of triangular graph paper to plot the three measurements against one another. All the land tortoise species formed a tight cluster of points in the upper part of the triangle; all the water turtles cluster in the lower part of the triangular graph. There was no overlap, except when they added some species that spend time both in water and on land. Sure enough, these amphibious species show up on the triangular graph approximately half way between the ‘wet cluster' of sea turtles and the ‘dry cluster' of land tortoises. 'The next step was to determine where the fossil fell. The bones of and leave us in no doubt. Their points on the graph are right in the thick of the dry cluster. Both these fossils were dry-land tortoises. They come from the era before our turtles returned to the water.
You might think, therefore, that modem land tortoises have probably stayed on land ever since those early terrestrial times, as most mammals did after a few of them went back to the sea. But apparently not. If you draw out the family tree of all modern turtles and tortoises, nearly all the branches are aquatic. Today’s land tortoises constitute a single branch, deeply nested among branches consisting of aquatic turtles. This suggests that modern land tortoises have not stayed on land continuously since the time of . Rather, their ancestors were among those who went back to the water, and they then re-emerged back onto the land in (relatively) more recent times.
27. What had to transfer from sea to land before any animals could migrate?
28. Which TWO processes are mentioned as those in which animals had to make big changes as they moved onto land?
29. Which physical feature. possessed by their ancestors, do whales lack?
30. Which animals might ichthyosaurs have resembled?
Do the following statements agree with the information given in Reading Passage 3?
In boxes on your answer sheet, write
if the statement agrees with the information
if the statement contradicts the information
if there is no information on this more than once.
31.Turtles were among the first group of animals to migrate back to the sea.
32.It is always difficult to determine where an animal lived when its fossilized remains are incomplete.
33.The habitat of ichthyosaurs can be determined by the appearance of their fossilized remains.
Write your answers in boxes 34-39 on your answer sheet.
71 species of living turtles and tortoises were examined and a total of ................were taken from the bones of their forelimbs.
The data was recorded on a ................... (necessary for comparing the information). Outcome: Land tortoises were represented by a dense .................. of points towards the top. Sea turtles were grouped together in the bottom part.
The same data was collected from some living .................. species and added to the other results. Outcome: The points for these species turned out to be positioned about .................. up the triangle between the land tortoises and the sea turtles.
Bones of R quenstedti and P talampayensis were examined in a similar way and the results added.
Outcome: The position of the points indicated that both these ancient creatures were
from the passage for each answer
A they are able to adapt to life in extremely dry environments.
B their original life form was a kind of primeval bacteria,
C they have so much in common with sea turtles.
D they have made the transition from sea to land more than once.