Why are blue whales so enormous? - Asha de Vos
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0:31 - 0:33Blue whales are the largest animals
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0:33 - 0:35that have ever roamed the planet.
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0:35 - 0:38They're at least two times as big as the biggest dinosaurs,
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0:39 - 0:40"That's big!"
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0:40 - 0:42the length of a basketball court,
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0:42 - 0:45and as heavy as 40 African elephants.
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0:45 - 0:47If that's not enough to make you marvel,
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0:47 - 0:49here's something that will.
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0:49 - 0:50They're grown to this enormous size
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0:50 - 0:55by feeding exclusively on tiny shrimp-like creatures called krill
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0:58 - 1:01that are no bigger than your little finger.
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1:01 - 1:03In many ways, the sheer size of krill
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1:03 - 1:06seems to have driven the evolution of the blue whale.
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1:08 - 1:10See, krill are so small
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1:10 - 1:12but are found in dense patches.
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1:12 - 1:13For increased efficiency,
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1:13 - 1:14blue whales have evolved
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1:14 - 1:16to use a feeding strategy
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1:16 - 1:18called lunge feeding.
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1:18 - 1:21Basically, the whale accelerates towards a prey patch
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1:21 - 1:23and opens its mouth wide.
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1:23 - 1:26To increase the capacity, its mouth expands.
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1:26 - 1:28The special, accordion-like blubber layer
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1:28 - 1:30that extends from its snout to its belly button
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1:30 - 1:33enables the whale to engulf large quantities
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1:33 - 1:35of prey-laden water.
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1:43 - 1:44With each giant gulp,
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1:44 - 1:48the whale takes in 125% of its body weight
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1:48 - 1:50in water and krill.
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1:50 - 1:52The whale must then expel the water
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1:52 - 1:54while retaining the yummy krill.
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1:54 - 1:56To do this, it uses its baleen,
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1:56 - 1:58the comb-like structure made of the same stuff
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1:58 - 2:01our nails and hair are made of,
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2:01 - 2:03and its tongue.
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2:09 - 2:11It's pretty crazy that the blue whale's heart
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2:11 - 2:13is as big as a small car,
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2:13 - 2:15a child could crawl through its arteries,
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2:15 - 2:17its tongue weighs as much as an elephant,
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2:17 - 2:20but its esophagus is so small,
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2:20 - 2:23the whale could choke on a loaf of bread.
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2:23 - 2:25These whales are really not designed
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2:25 - 2:27to feed on anything larger than krill.
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2:31 - 2:36It's estimated that blue whales eat four tons of krill per day.
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2:36 - 2:37Because of the incredible design,
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2:37 - 2:39each dive provides the blue whale
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2:39 - 2:42with 90 times as much energy as is used.
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2:42 - 2:47Every mouthful of krill provides almost 480,000 calories,
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2:47 - 2:52the same amount you get from eating 1,900 hamburgers.
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2:55 - 2:58But, why are blue whales so big?
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2:58 - 2:59Blue whales are considerably larger
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2:59 - 3:02than the largest living land animal, the elephant.
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3:02 - 3:04The heavier an animal is,
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3:04 - 3:06the greater its relative surface area.
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3:06 - 3:08As weight increases,
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3:08 - 3:10there's a point at which the legs of that animal
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3:10 - 3:12would simply collapse.
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3:12 - 3:14That explains why elephants don't stand
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3:14 - 3:17on the delicate legs of a horse.
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3:17 - 3:19They need legs shaped like stout pedestals
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3:19 - 3:22to hold their bodies up against gravity.
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3:25 - 3:28In water, the situation is quite different.
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3:28 - 3:31Buoyancy counteracts the gravitational pull on the body
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3:31 - 3:33and their great bulk is therefore partially supported
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3:33 - 3:35by the water.
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3:35 - 3:37So, the ocean is a great place for species
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3:37 - 3:39that want to grow bigger.
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3:39 - 3:42The other secret to their size is their diet.
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3:42 - 3:44By evolving such a huge mouth,
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3:44 - 3:47the whale's have specialized to catch enormous quantities
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3:47 - 3:49of highly abundant and nutritious prey,
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3:49 - 3:53which provides the energy needed to grow so big.
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3:56 - 3:58But, now maybe you're wondering
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3:58 - 4:01why blue whales aren't any bigger?
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4:01 - 4:03After all, the ocean sounds like nirvana
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4:03 - 4:04for any growing beast.
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4:04 - 4:07Well, while lunge feeding may have allowed blue whales
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4:07 - 4:09to become the biggest animal
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4:09 - 4:10to have ever roamed the planet,
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4:10 - 4:14by enabling them to feed efficiently in dense prey patches,
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4:14 - 4:16it isn't cost free.
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4:16 - 4:19Scientists compared all the costs involved with lunge feeding
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4:19 - 4:21to the energy gained from the krill they eat.
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4:21 - 4:25What they found is that when the whale's body increases in size,
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4:25 - 4:27the energy that body demands rises faster
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4:27 - 4:31than the extra energy they get from their food.
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4:31 - 4:36Feeding whales needs 15 times the energy required to remain still
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4:36 - 4:40and 5 times more energy than used when swimming.
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4:40 - 4:41Calculations show
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4:41 - 4:45that the largest a lunge feeder can grow is 33 meters,
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4:45 - 4:47pretty much blue whale size.
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4:47 - 4:50Turns out blue whales have a lot to thank krill for:
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4:50 - 4:51neat, evolutionary adaptations
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4:51 - 4:55that would not have been possible if krill were not so small.
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4:55 - 4:57It's incredible that these tiny creatures
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4:57 - 5:00have allowed blue whales to really push the limits
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5:00 - 5:02of size on our planet.
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5:02 - 5:04Makes you wonder if that old adage,
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5:04 - 5:06"You are what you eat,"
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5:06 - 5:09really does apply in blue whale world.
- Title:
- Why are blue whales so enormous? - Asha de Vos
- Description:
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View full lesson: http://ed.ted.com/lessons/why-are-blue-whales-so-enormous-asha-de-vos
Blue whales are the largest animals on the planet, but what helps them grow to the length of a basketball court? Asha de Vos explains why the size of krill make them the ideal food for the blue whale -- it's as if the blue whale was made to eat krill (and krill was made to be eaten by the blue whale).
Lesson by Asha De Vos, animation by Cognitive Media.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:21
Andrea McDonough commented on English subtitles for Why are blue whales so enormous? - Asha de Vos | ||
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