What is Evolution? — Transcript

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1. 0:00This Miles was here of Stated Clearly was made possible through generous donations
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4. 0:07and contributions from individual viewers like you.
5. 0:13Stated Clearly Presents
6. 0:18What is Evolution?
7. 0:20In biology,
8. 0:22the Theory of Evolution doesn't tell us exactly how life began on earth -
9. 0:26but it helps us understand how life -
10. 0:28once it came into existence -
11. 0:30diversified into the many incredible forms we see now and in the fossil
12. 0:34record.
13. 0:36It also helps us make sense of the way in which modern creatures
14. 0:39continue to adapt and change today.
15. 0:43In biology,
16. 0:45evolution can be defined as any changed in the heritable traits
17. 0:49(those are physical traits like fur color in mice
18. 0:52spots on the wings of butterflies
19. 0:54or instinctive behaviors like the way in which dogs greet their friends with a sniff)
20. 0:59within a population
21. 1:00across generations.
22. 1:03This definition can be a bit confusing
23. 1:06so let's see how it works
24. 1:08all healthy living things from
25. 1:10single celled amoebas to
26. 1:12flowers to dolphins
27. 1:14are capable
28. 1:15of reproduction.
29. 1:17We have children,
30. 1:18we make copies of ourselves.
31. 1:20We do this by duplicating DNA
32. 1:23and passing that DNA on to future generations.
33. 1:27DNA is a chain like chemical stored inside each one of your cells
34. 1:31which tells them how to grow and function.
35. 1:34Your DNA contains coded information
36. 1:36on how to build you.
37. 1:38Tthe information in your DNA is different than that of say a daffodils DNA,
38. 1:43which is why you look and function differently than a daffodil.
39. 1:46The information in your DNA is slightly different
40. 1:49than that of Elvis Presley,
41. 1:50which is one of many reasons you don't look a and act quite like he did.
42. 1:55Single celled amoebas and
43. 1:56other simple creatures
44. 1:58reproduce by copying their DNA - inside their guts -
45. 2:02moving both copies to either side of their body,
46. 2:04splitting in two right down the middle
47. 2:06and then growing back to full size.
48. 2:09If all goes well the two new amoebas will be exact copies of each other.
49. 2:13But in nature things aren't always perfect.
50. 2:18When DNA is being copied,
51. 2:20errors can occur
52. 2:21which modify the DNA code.
53. 2:24This is what we call a DNA mutation.
54. 2:28can produce variation in the body shape and function of the creature who inherits
55. 2:32the modified DNA.
56. 2:34In this case,
57. 2:36our new little friend has an arm that stretches extra long.
58. 2:39If he survives long enough to grow and reproduce
59. 2:42that extra stretchy arm (which
60. 2:44is now coded for his DNA)
61. 2:47will be passed on to his children.
62. 2:49Evolution:
63. 2:51any change in the heritable traits
64. 2:53within a population
65. 2:54across generations
66. 2:56has officially occurred.
67. 3:00reproduction for dolphins and badgers and people
68. 3:04is a little more complicated.
69. 3:06we have to find ourselves a partner.
70. 3:08When to a badgers get together and
71. 3:11you know...fall in love
72. 3:13a sperm cell from the father which contains a copy of half of his DNA
73. 3:17- only half -
74. 3:19combines with the egg cell of the mother
75. 3:21which contains half a copy of her DNA
76. 3:24the result is a brand new cell with a complete set of DNA instructions
77. 3:29all the information needed to divide and grow up
78. 3:32into a brand new badger
79. 3:35the new child matures to be similar to her parents
80. 3:38but also unique
81. 3:39because she developed some traits from her mother's DNA
82. 3:42and some from her father
83. 3:44her new combination of traits can be passed on to her children and again
84. 3:48Evolution: any change in the heritable traits
85. 3:51within a population
86. 3:53across generations
87. 3:54has officially occurred
88. 3:57Besides the unique recombination of her parents traits
89. 4:01she might also have developed some completely new traits of her own due to
90. 4:04DNA mutations
91. 4:07maybe extra hairy ears for example
92. 4:10if she survives long enough to have kids
93. 4:12her DNA will combine with the DNA of her partner
94. 4:15and she'll pass on those extra hairy ears to at least some of her children
95. 4:20again
96. 4:21Evolution has officially occurred
97. 4:24so there you have it
98. 4:26evolution is really pretty simple
99. 4:28scientists and normal folks everywhere
100. 4:31witness evolution happening all the time
101. 4:34small changes like the ones we've seen here can add up over multiple
102. 4:37generations to create dramatic
103. 4:39changes
104. 4:41if you were to go back in time just a few thousand years
105. 4:45you'd find that all dogs for example
106. 4:47originally evolved from an ancestral group of gray wolves
107. 4:52the evolution of those wolves from
108. 4:54generation to generation
109. 4:56was guided
110. 4:57by humans
111. 4:59people were selecting wolves with the traits they liked
112. 5:02letting them breed
113. 5:03and then only keeping the puppies with the most desirable traits
114. 5:07as time went on
115. 5:08different breeders preferred dogs with different features
116. 5:11some selected from large size
117. 5:13some for small size, some for brains
118. 5:16others for brawn
119. 5:18today wolves have branched out into hundreds of breeds
120. 5:21very few of which look and behave much like their ancestors
121. 5:26a massive amount of observable evidence from many different fields such as
122. 5:30Genetics
123. 5:31chemistry, paleontology, and mathematics
124. 5:35overwhelmingly suggest just like all dogs share a common ancestor
125. 5:40all living things
126. 5:41me,
127. 5:42you, puffer fish
128. 5:44banana trees, if you go back far enough
129. 5:48also share a common ancestor
130. 5:50we are literally related
131. 5:53we don't know what the first life form was or exactly how it came to be
132. 5:57but the simple process of reproduction
133. 6:00with variation over billions of years
134. 6:03looks to be responsible for all the diversity of life we see today
135. 6:08now you might be saying wait a minute, hold on here -
136. 6:11isn't evolution
137. 6:13random?
138. 6:14To do something functional like turn a wolf into an adorable
139. 6:18mini poodle
140. 6:19random evolution had to be carefully guided
141. 6:22by an intelligent dog breeder
142. 6:25researchers claim that all mammals evolved from an ancient shrew-like
143. 6:28creature
144. 6:29but the difference between a shrew
145. 6:31and an elephant
146. 6:32is far greater than that of a wolf
147. 6:34and a poodle
148. 6:35who guided that process?
149. 6:37who
150. 6:38was the breeder
151. 6:40in the mid eighteen hundreds two men
152. 6:42Charles Darwin
153. 6:43and Alfred Russel Wallace independently discovered
154. 6:47that a breeder is not necessarily needed
155. 6:50there is another force capable of guiding random evolution
156. 6:53to produce order and complex function
157. 6:57they called it natural selection
158. 6:59(Which happens to be the entire topic of our next video)
159. 7:03but before you move on
160. 7:04let's recap what we've learned so far:
161. 7:07Biological evolution
162. 7:09is any change in the heritable traits
163. 7:12within a population
164. 7:13across generations.
165. 7:15All healthy living things can make copies of themselves -
166. 7:19but they do so imperfectly.
167. 7:21Small variations can build up over generations to create dramatic
168. 7:24differences
169. 7:26in the body form and function
170. 7:28of living creatures.
171. 7:29Evidence overwhelmingly suggests that all life on earth is related.
172. 7:35So remember -
173. 7:36next time you invite family and friends
174. 7:39over for a holiday feast
175. 7:41you're actually just inviting family!
176. 7:43That includes the turkey,
177. 7:45and the pumpkin
178. 7:46in the pumpkin pie.
179. 7:49I'm Jon Perry and that's evolution
180. 7:51Stated Clearly
181. 7:58Thanks for watching our show, I hope you enjoyed it.
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