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From the Ted Talk by Kenny Coogan: Why are sloths so slow?

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In 1796, Thomas Jefferson received a box of bones he couldn't infteidy. A long, sharp claw rieedmnd him of a lion, but the arm bones suggested a larger animal, one about three meters long. tnkinihg it might be huge unknown species of North American lion, Jefferson warned explorers leiws and Clark to keep an eye out for this mysterious predator. But Jefferson's box of bones didn't come from a lion. They came from an ecxitnt giant sloth. preishotric ground sloths first appeared around 35 million years ago. Dozens of species lievd across North, Central and South America, alongside other ancient creatures like msotaodns and giant armadillos. Some ground sloths, like the megalonychid, were cat-sized, but many were massive. Jefferson's sloth, Megalonyx, weighed about a ton, and that was slmal compared to megatherium, which could reach six metric tons, as much as an elephant. They ambled through the forests and savannas using their stnorg arms and sharp claws to uproot plants and clmib teers, grazing on grasses, leaves, and prehistoric avocados. In fact, we might not have aaocovds today if not for the giant sloths. Smaller animals couldn't swallow the avocado's huge seed, but the sloths could, and they spread avocado trees far and wide. Ground sloths flourished for millions of yraes, but around 10,000 years ago, they started disappearing along with the wesetrn Hemisphere's other giant mammals. Researchers think that gonrud sloths could have been pushed out by an oncoming ice age, or competition with other species, maybe humans, who arrived in the region around the time most of the sloths went extinct. Some of the selmlar sloths did survive and metigard to the treetops. Today, there are six species left living in the rainforest canopies of Central and South America. hangnig out in the trees is a good way to aoivd peordtars, and there are plenty of laeevs to eat. But this diet has its drawbacks. Animals extract energy from food and use that energy to move around, maintain their body temperature, keep their organs working, and all the other activities necessary for survival. But leaves don't contain much energy, and that which they do have is toguh to extract. Most herbivores supplement a leafy diet with higher eergny foods like fruit and sdees. But sloths, especially three-toed sloths, rely on leaves almost exclusively. They've evolved finely tenud setrtgaeis for coping with this restricted diet. First, they extract as much energy from their food as possible. shtols have a multi-chambered stomach that tekas up a third of their body, and depending on the species, they can spend five to seven days, or even wkees, processing a meal. The other piece of the puzzle is to use as little energy as possible. One way sloths do this is, of course, by not moving very much. They spend most of their time eating, resting, or sleeping. They descend from the canopy just once a week for a bathroom break. When sloths do move, it's not very fast. It would take a sloth about five miteuns to cross an average neighborhood street. This unhurried approach to life means that sloths don't need very much muscle. In fact, they have about 30% less mcsule mass than other animals their size. Sloths also use less energy to keep themselves warm because their body tepeurmrtae can fluctuate by about five degrees csuelis, less than a cold-blooded reptile, but more than most mammals. These physical and behavioral adaptations minimize the sloth's energy expenditure, or metabolic rate. Three-toed sloths have the slowest metabolism of any mammal. The gniat panda is second slowest, and two-toed sloths come in third. Moving slowly has allowed sloths to thrive in their treetop habitat. But it's also made the sloths themselves a great habitat for other organisms, including algae, which provides a little extra camouflage, and maybe even a snack. Sloths may not be giant anymore, but that doesn't make them any less remarkable.

Open Cloze

In 1796, Thomas Jefferson received a box of bones he couldn't ________. A long, sharp claw ________ him of a lion, but the arm bones suggested a larger animal, one about three meters long. ________ it might be huge unknown species of North American lion, Jefferson warned explorers _____ and Clark to keep an eye out for this mysterious predator. But Jefferson's box of bones didn't come from a lion. They came from an _______ giant sloth. ___________ ground sloths first appeared around 35 million years ago. Dozens of species _____ across North, Central and South America, alongside other ancient creatures like _________ and giant armadillos. Some ground sloths, like the megalonychid, were cat-sized, but many were massive. Jefferson's sloth, Megalonyx, weighed about a ton, and that was _____ compared to megatherium, which could reach six metric tons, as much as an elephant. They ambled through the forests and savannas using their ______ arms and sharp claws to uproot plants and _____ _____, grazing on grasses, leaves, and prehistoric avocados. In fact, we might not have ________ today if not for the giant sloths. Smaller animals couldn't swallow the avocado's huge seed, but the sloths could, and they spread avocado trees far and wide. Ground sloths flourished for millions of _____, but around 10,000 years ago, they started disappearing along with the _______ Hemisphere's other giant mammals. Researchers think that ______ sloths could have been pushed out by an oncoming ice age, or competition with other species, maybe humans, who arrived in the region around the time most of the sloths went extinct. Some of the _______ sloths did survive and ________ to the treetops. Today, there are six species left living in the rainforest canopies of Central and South America. _______ out in the trees is a good way to _____ _________, and there are plenty of ______ to eat. But this diet has its drawbacks. Animals extract energy from food and use that energy to move around, maintain their body temperature, keep their organs working, and all the other activities necessary for survival. But leaves don't contain much energy, and that which they do have is _____ to extract. Most herbivores supplement a leafy diet with higher ______ foods like fruit and _____. But sloths, especially three-toed sloths, rely on leaves almost exclusively. They've evolved finely _____ __________ for coping with this restricted diet. First, they extract as much energy from their food as possible. ______ have a multi-chambered stomach that _____ up a third of their body, and depending on the species, they can spend five to seven days, or even _____, processing a meal. The other piece of the puzzle is to use as little energy as possible. One way sloths do this is, of course, by not moving very much. They spend most of their time eating, resting, or sleeping. They descend from the canopy just once a week for a bathroom break. When sloths do move, it's not very fast. It would take a sloth about five _______ to cross an average neighborhood street. This unhurried approach to life means that sloths don't need very much muscle. In fact, they have about 30% less ______ mass than other animals their size. Sloths also use less energy to keep themselves warm because their body ___________ can fluctuate by about five degrees _______, less than a cold-blooded reptile, but more than most mammals. These physical and behavioral adaptations minimize the sloth's energy expenditure, or metabolic rate. Three-toed sloths have the slowest metabolism of any mammal. The _____ panda is second slowest, and two-toed sloths come in third. Moving slowly has allowed sloths to thrive in their treetop habitat. But it's also made the sloths themselves a great habitat for other organisms, including algae, which provides a little extra camouflage, and maybe even a snack. Sloths may not be giant anymore, but that doesn't make them any less remarkable.

Solution

  1. celsius
  2. muscle
  3. seeds
  4. tuned
  5. giant
  6. leaves
  7. minutes
  8. weeks
  9. ground
  10. reminded
  11. tough
  12. lived
  13. predators
  14. lewis
  15. small
  16. identify
  17. mastodons
  18. avocados
  19. strategies
  20. trees
  21. energy
  22. western
  23. avoid
  24. takes
  25. smaller
  26. prehistoric
  27. migrated
  28. extinct
  29. years
  30. climb
  31. thinking
  32. strong
  33. sloths
  34. temperature
  35. hanging

Original Text

In 1796, Thomas Jefferson received a box of bones he couldn't identify. A long, sharp claw reminded him of a lion, but the arm bones suggested a larger animal, one about three meters long. Thinking it might be huge unknown species of North American lion, Jefferson warned explorers Lewis and Clark to keep an eye out for this mysterious predator. But Jefferson's box of bones didn't come from a lion. They came from an extinct giant sloth. Prehistoric ground sloths first appeared around 35 million years ago. Dozens of species lived across North, Central and South America, alongside other ancient creatures like mastodons and giant armadillos. Some ground sloths, like the megalonychid, were cat-sized, but many were massive. Jefferson's sloth, Megalonyx, weighed about a ton, and that was small compared to megatherium, which could reach six metric tons, as much as an elephant. They ambled through the forests and savannas using their strong arms and sharp claws to uproot plants and climb trees, grazing on grasses, leaves, and prehistoric avocados. In fact, we might not have avocados today if not for the giant sloths. Smaller animals couldn't swallow the avocado's huge seed, but the sloths could, and they spread avocado trees far and wide. Ground sloths flourished for millions of years, but around 10,000 years ago, they started disappearing along with the Western Hemisphere's other giant mammals. Researchers think that ground sloths could have been pushed out by an oncoming ice age, or competition with other species, maybe humans, who arrived in the region around the time most of the sloths went extinct. Some of the smaller sloths did survive and migrated to the treetops. Today, there are six species left living in the rainforest canopies of Central and South America. Hanging out in the trees is a good way to avoid predators, and there are plenty of leaves to eat. But this diet has its drawbacks. Animals extract energy from food and use that energy to move around, maintain their body temperature, keep their organs working, and all the other activities necessary for survival. But leaves don't contain much energy, and that which they do have is tough to extract. Most herbivores supplement a leafy diet with higher energy foods like fruit and seeds. But sloths, especially three-toed sloths, rely on leaves almost exclusively. They've evolved finely tuned strategies for coping with this restricted diet. First, they extract as much energy from their food as possible. Sloths have a multi-chambered stomach that takes up a third of their body, and depending on the species, they can spend five to seven days, or even weeks, processing a meal. The other piece of the puzzle is to use as little energy as possible. One way sloths do this is, of course, by not moving very much. They spend most of their time eating, resting, or sleeping. They descend from the canopy just once a week for a bathroom break. When sloths do move, it's not very fast. It would take a sloth about five minutes to cross an average neighborhood street. This unhurried approach to life means that sloths don't need very much muscle. In fact, they have about 30% less muscle mass than other animals their size. Sloths also use less energy to keep themselves warm because their body temperature can fluctuate by about five degrees Celsius, less than a cold-blooded reptile, but more than most mammals. These physical and behavioral adaptations minimize the sloth's energy expenditure, or metabolic rate. Three-toed sloths have the slowest metabolism of any mammal. The giant panda is second slowest, and two-toed sloths come in third. Moving slowly has allowed sloths to thrive in their treetop habitat. But it's also made the sloths themselves a great habitat for other organisms, including algae, which provides a little extra camouflage, and maybe even a snack. Sloths may not be giant anymore, but that doesn't make them any less remarkable.

Frequently Occurring Word Combinations

ngrams of length 2

collocation frequency
ground sloths 3

Important Words

  1. activities
  2. adaptations
  3. age
  4. algae
  5. allowed
  6. ambled
  7. america
  8. american
  9. ancient
  10. animal
  11. animals
  12. anymore
  13. appeared
  14. approach
  15. arm
  16. armadillos
  17. arms
  18. arrived
  19. average
  20. avocado
  21. avocados
  22. avoid
  23. bathroom
  24. behavioral
  25. body
  26. bones
  27. box
  28. break
  29. camouflage
  30. canopies
  31. canopy
  32. celsius
  33. central
  34. clark
  35. claw
  36. claws
  37. climb
  38. compared
  39. competition
  40. coping
  41. creatures
  42. cross
  43. days
  44. degrees
  45. depending
  46. descend
  47. diet
  48. disappearing
  49. dozens
  50. drawbacks
  51. eat
  52. eating
  53. elephant
  54. energy
  55. evolved
  56. exclusively
  57. expenditure
  58. explorers
  59. extinct
  60. extra
  61. extract
  62. eye
  63. fact
  64. fast
  65. finely
  66. flourished
  67. fluctuate
  68. food
  69. foods
  70. forests
  71. fruit
  72. giant
  73. good
  74. grasses
  75. grazing
  76. great
  77. ground
  78. habitat
  79. hanging
  80. herbivores
  81. higher
  82. huge
  83. humans
  84. ice
  85. identify
  86. including
  87. jefferson
  88. larger
  89. leafy
  90. leaves
  91. left
  92. lewis
  93. life
  94. lion
  95. lived
  96. living
  97. long
  98. maintain
  99. mammal
  100. mammals
  101. mass
  102. massive
  103. mastodons
  104. meal
  105. means
  106. megalonychid
  107. megalonyx
  108. megatherium
  109. metabolic
  110. metabolism
  111. meters
  112. metric
  113. migrated
  114. million
  115. millions
  116. minimize
  117. minutes
  118. move
  119. moving
  120. muscle
  121. mysterious
  122. neighborhood
  123. north
  124. oncoming
  125. organisms
  126. organs
  127. panda
  128. physical
  129. piece
  130. plants
  131. plenty
  132. predator
  133. predators
  134. prehistoric
  135. processing
  136. pushed
  137. puzzle
  138. rainforest
  139. rate
  140. reach
  141. received
  142. region
  143. rely
  144. remarkable
  145. reminded
  146. reptile
  147. researchers
  148. resting
  149. restricted
  150. savannas
  151. seed
  152. seeds
  153. sharp
  154. size
  155. sleeping
  156. sloth
  157. sloths
  158. slowest
  159. slowly
  160. small
  161. smaller
  162. snack
  163. south
  164. species
  165. spend
  166. spread
  167. started
  168. stomach
  169. strategies
  170. street
  171. strong
  172. suggested
  173. supplement
  174. survival
  175. survive
  176. swallow
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  178. temperature
  179. thinking
  180. thomas
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  184. ton
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  186. tough
  187. trees
  188. treetop
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  190. tuned
  191. unhurried
  192. unknown
  193. uproot
  194. warm
  195. warned
  196. week
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  198. weighed
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  200. wide
  201. working
  202. years