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00:00Dinosaurs.
00:15The most fantastic animals in the history of life on Earth.
00:22And yet their extinction remains a mystery.
00:33Here at New York City's Museum of Natural History,
00:36visitors are greeted by an imposing prehistoric creature.
00:47Berosaurus, whose name means heavy lizard, stretched a staggering 80 feet long
00:54and stood as tall as a five-story building.
01:00This enormous plant-eating dinosaur lived during the Jurassic period some 150 million years ago.
01:17At the time, dense forests up to 300 feet tall blanketed the Earth.
01:32Berosaurs consumed huge quantities of leaves from these giant stands.
01:44Throughout the ages, animals of every shape and size have relied on plants for sustenance.
01:52Whenever new flora appear, the effect on the animal kingdom can be dramatic.
02:00In the rise and fall of dinosaurs, the evolution of plants played a surprisingly significant role.
02:09The N beading W Friedman, the engine of several lands,
02:15the environmental CP arean-based,
02:24the form of georgian lac reopenards.
02:26ORCHESTRA PLAYS
02:56ORCHESTRA PLAYS
03:26Earth, half a billion years ago, was a place of striking contrasts.
03:35Long before the first four-legged creature ventured on to shore, before dinosaurs were even a dream, Earth was a barren wasteland.
03:47But the ocean teemed with plants and animals of all shapes and sizes.
03:54Beyond the water's edge, no living thing could survive.
04:03But these lifeless landmasses would soon witness change.
04:13Vast islands of rock and sand collided again and again, creating larger continents.
04:22The collisions thrust mounds of Earth upward through the planet's fault lines.
04:29Over time, these rising hills would evolve into the world's great mountain ranges.
04:39These lofty giants caused major shifts in the climate.
04:45The deluges carved winding paths through mountainsides, converging into powerful bodies of water.
04:52These freshwater rivers were new geological phenomena, neither land nor sea.
05:07In time, our sea-dwelling ancestors would feel their lure and make their next evolutionary move.
05:22Throughout Earth's history, plants have always been a step ahead of animals.
05:29About 400 million years ago, plants began to sprout along the water's edge.
05:36In time, insects and the common ancestor to both dinosaurs and humans, amphibians, began to populate this new green landscape.
05:49Fifty million years after their arrival, a few simple plants had evolved into lush forests, habitats that would lure the first curious river creature onto land.
06:05But these hardy giants could survive and breed only in proximity to water.
06:23The trees were actually tree ferns with stems and leaves.
06:34with stems and leaves that reproduced through spores.
06:40Earth's early trees had no flowers or seeds.
06:46Vegetation had yet to appear further inland.
06:49So animal life was also confined to the shores.
06:52The badlands of Arizona.
07:10Hidden in this desolate landscape are some of the earliest fossils of plants that moved inland.
07:16This giant tree has kept a lonely vigil here for millions of years.
07:23But in its day, it was a pioneer of sorts.
07:28Born on the wind, it arrived at this spot as seed.
07:34This is a 320 million year old plant fossil.
07:47Its round seed harboring a tree.
07:50Because trees had deep roots, they could weather many seasons even on arid land.
08:00Over the course of history, many plants, even the spectacular tree ferns, faded from record.
08:11But a new class of plants, the gymnosperms, was on the rise.
08:18These were plants with exposed seeds, usually contained in a type of cone.
08:25Gymnosperms developed a new method of reproduction.
08:29Their seeds were fertilized by clouds of wind-blown pollen that settled on the female reproductive organ, the pistil.
08:44Plants like these conifers could now proliferate inland,
08:48awaiting the day of the creature that would rule the forest for years, the dinosaur.
08:55230 million years ago, during the Triassic period, when the first dinosaurs would appear,
09:05the planet underwent another major transformation.
09:10The supercontinent of Pangaea began to break apart.
09:16In the wake of continued violent volcanic activity,
09:21the amount of carbon dioxide in the atmosphere was four to eight-fold what it is today.
09:28For plants that photosynthesize using sunlight and carbon dioxide,
09:34this was an ideal environment.
09:37Back in the Triassic age, North America's forests probably looked a lot like this.
09:54Enormous trees dense with foliage stretching toward the sunlight.
10:13Land that for eons lay exposed to the sun's harsh rays, now rested under a protective canopy.
10:23Deep roots collected water, and the forest prospered.
10:30The new plant life was an attractive food source for the herbivores that were populating land's interior,
10:43and later the meat-eating reptiles that preyed on them.
10:47Among these distant relatives of Ichthyostega, the first creature to set foot on land,
10:56were the world's first dinosaurs.
11:00This Triassic lizard dates back 225 million years.
11:15Lacking the sharp teeth of its carnivorous kin,
11:21it's considered to be one of the earliest plant-eating dinosaurs.
11:25This tiny creature, less than three feet long, was less than ferocious.
11:34But over nearly 50 million years, the small dinosaurs began to grow in stature and design.
11:48From grazers to high browsers, their size reflected a wide range of feeding adaptations.
11:59The reign of the dinosaur began in the planet's great forests.
12:13Dinosaurs of fantastic proportion had evolved perhaps to take advantage of the plentiful food supply in the forest canopy.
12:32Unlike reptiles, dinosaurs walked on sturdy legs that allowed them to take long, efficient strides,
12:49and supported their enormous body weight, especially while feeding.
13:02By developing longer necks, the Berosaurus and other sauropods could feast on leaves in the treetops,
13:09beyond the reach of other animals.
13:18The sauropods had extremely crude dental structures, long and narrow peg-like teeth.
13:25Without molars like animals that evolved later on, these dinosaurs couldn't grind their food.
13:37Plant-eating dinosaurs in the Jurassic period swallowed stones quite regularly to help them break up the plant material that they swallowed.
13:46Sauropods did not want to add too much weight onto the head, and of course teeth are very heavy.
13:51So if sauropods were grinding up their food in their mouths, they would have a problem with this,
13:57because that would mean they would have to have a lot of teeth in their jaws.
14:00The teeth are heavy, and that gives them a balance problem with their long necks.
14:04So what sauropods did instead was swallow stones, which went down into possibly a gizzard in the gut region,
14:12but certainly into the stomach as well, and the stones would rub together and grind up the plant material.
14:19Barosaurs only use their limited jaws for simple tasks, carrying food from the forest canopy.
14:32The gymnosperms of their era had softer leaves than today's conifers.
14:47No one knows how much food these huge sauropods had to consume to survive, but their appetites were gargantuan.
14:54Scientists estimate that their daily diet may have exceeded a half ton of vegetation.
15:11Grazing voraciously, dinosaurs, with the help of newly arrived insects, were cutting a devastating swath across the landscape.
15:19By the end of the Jurassic period, more than ten varieties of sauropods and a range of carnivorous dinosaurs roamed the North American continent.
15:40While browsing dinosaurs grew in size and range, plants were undergoing their own evolutionary breakthrough.
16:01This is West Water Canyon in Utah.
16:07Ancient plant fossils of an entirely new variety have surfaced here.
16:13Neither a tree fern nor a gymnospern, these plants had oval-shaped leaves.
16:22Their arrival would revolutionize the plant kingdom, and in time, alter the ecology of the earth.
16:32Dr. Peter Crane, a biologist with Chicago's Field Museum of Natural History, has been sifting through layers of time, studying the origins of this great change.
16:51Rocks from the Utah desert are thoroughly washed in water, then gradually dissolved with weak acid to separate stone from plant life.
17:06Soon, a tiny flower petals, shaped like a tulip, emerges.
17:13The unlikely catalyst of major change in the earth's ecology, the angiosperm, or flowering plant.
17:25The ancestor of the modern-day magnolia may be the earliest flower on record.
17:37Inside the flower, a tiny gold bug coming out of the pupil stage.
17:44It's likely that relatives of this insect contributed to the revolution of flowering plants.
17:57Jurassic forests provided a sumptuous table for the gold bug and other new insect life.
18:14Pollen from flowering plants drifted through the forest like a soft rain.
18:31As the tiny insect moved from plant to plant, pollen stuck to its legs and was delivered to the flower's reproductive organs, or pistils, to form new seed.
18:43With the help of the gold bug, flowers spread across the landscape.
18:50Plants that received enough pollen developed a range of distinctive colors, shapes, and scents to attract more insects.
19:10In his outdoor laboratory, Cornell University biologist Dr. Carl Nicholas observes nature's age-old alliances at work.
19:28He believes that earth's early plants and insects formed relationships for the same reason, mutual survival.
19:37Insect pollination allows a plant to transport pollen from one individual to the next, using the brain of the insect to identify the same kind of plant as the donor of the pollen.
19:51So, for example, you can have angiosperms that are separated by many miles.
19:55Two flowering plants of the same species separated by many miles and the insect can transport pollen over that mileage.
20:02Plants can't move, but insects can.
20:05Gymnosperms tend to rely on wind for transport of pollen, so they can transport their pollen only a short, relatively shorter distance.
20:12So you can get widely scattered angiosperms that are still reproductively successful.
20:17If you widely scatter pine trees, they're not as reproductively successful.
20:24The new flowering angiosperms had another advantage over other plants, the speed at which they reproduced.
20:36Gymnosperms, like cedars and pines, pollinated on the wind, had gained an evolutionary foothold millions of years earlier.
20:47But once their pollen reached the pistil, it took a full six months to a year for the fertilization process to complete.
20:55The new flowering plants were dramatically more efficient.
21:03Once the pollen grains reach the stigma or opening on the pistil, they germinate, extending a pollen tube to deliver sperm to the ovary.
21:16Fertilization takes only three minutes after an infusion of pollen.
21:23Even the slowest of plants can fertilize within 24 hours.
21:28During the Cretaceous, for the very first time, there was a partnership that was established between flowering plants and insects.
21:35Before that time, it was an antagonistic relationship. The insects were eating the plants.
21:41But with the evolution of flowering plants, a kind of hand-and-glove relationship began to evolve.
21:48Flowers started changing their reproductive structures to accommodate the insects that were visiting them.
21:54And insects were beginning to change their morphology, their shape, to accommodate the visiting of flowers.
22:00Nectar produced by flowering plants was a powerful lure for their partners in evolution.
22:19New insects like bees and butterflies appeared, and with them, new methods of pollination.
22:28Only one type of bee can help fertilize this ginger plant.
22:34Using its long tongue, it skillfully opens the petals of this flower.
22:41Pollen inside sticks to the bee's head and is later delivered to other flowers.
22:51The bee, in turn, is rewarded with nectar, off-limits to other species.
22:58Through co-evolution, a specialized one-on-one relationship between flowering plant and bee is established.
23:07The co-operative effort produced an explosion of insects and flora of virtually infinite texture and design.
23:19While dinosaurs may have dominated the ancient forests, insects and plants working together would survive the ages.
23:33Flowering plants soon dominated the temperate regions of the North American continent, and gymnosperms receded further north.
23:49As forests declined, Jurassic trees evolved defenses such as spiny leaves and bitter poisons in an attempt to stave off the grazing dinosaurs.
24:07But the slow-growing conifers could not compete with the burgeoning family of angiosperms.
24:19The success of these prolific plants may have pushed the berosaur to the brink of extinction.
24:35Layers of history reflect these changes.
24:42Cornell's Dr. Nicholas has collected more than 18,000 plant and insect specimens from around the world.
24:53These ancient fossils tell the story of life's evolutionary struggle.
25:04It's not just that animals eat plants, it's not that plants rely on some animals for their reproductive biology,
25:11but the entire ecosystem depends on very fragile linkages between different types of plants and animals, plants and plants, animals and animals.
25:22When we see changes in an ecosystem on a vast level like we do during the Cretaceous, there were many changes in the environment that were going on.
25:33And consequently there could have been many factors that were contributing to the extinction of dinosaurs and at the same time the rise of angiosperms.
25:41No change could have been more dramatic for the dinosaur than the decline of Earth's great conifer forests.
25:56Populations that had lived for millions of years on nature's bounty dwindled in the wake of change.
26:08The conifers that remain must have evolved their own survival strategies, perhaps acquiring tougher foliage the weak-jawed dinosaurs were not equipped to consume.
26:23The reasons for their extinction continue to baffle scientists.
26:27But an extensive fossil record shows that the once mighty Barosaurus vanished completely from the North American continent 130 million years ago.
26:43More than ten different species of dinosaurs left their footprints here during the Jurassic period.
26:53But by the Cretaceous, when flowering plants exploded onto the scene, all but one had become an ecological casualty.
27:01Alaska's North Slope.
27:11During much of the year, this land bordering the Arctic Ocean is blanketed by snow and ice.
27:21Beneath the permafrost are some of the world's largest oil reserves.
27:31But there are other ridges buried here.
27:36Hidden in the sedimentary layers are dinosaur fossils.
27:43A prehistoric graveyard that has attracted the attention of Dr. Elizabeth Browers of the U.S. Geological Survey and Dr. Ralph Taggart of Michigan State University.
27:59Together, they have unearthed fossils from the strata dating back to a period after the birth of angiosperms.
28:06Though not as extreme as today, the Arctic winter back then was dark and cold, temperatures dropping to freezing.
28:26The discovery of fossils here has overturned the long-held notion dinosaurs thrived only in temperate zones.
28:34Well, what kind of plants is it that's making up this organic horizon?
28:39Well, you can't tell there because it's too dark, but we could whack away at it.
28:43The purpose of this scientific expedition is to learn why some dinosaurs came to inhabit such a remote and inhospitable place.
28:52Oh, look at this. Conifer needles. Look at them.
28:57Oh, yeah.
28:58They're all through the rock.
28:59There's no flout, no leaves at all? Just the needles?
29:01No, no broad leaves.
29:02You know, that's the curious thing because that would be what these dinosaurs would have to eat.
29:08The hadrosaurs, of course, are plant-eaters.
29:10Yeah.
29:11We would estimate that temperatures during the time that these animals were living, and the conifers as well,
29:17was about six to eight degrees centigrade, mean annual temperature.
29:21And also, because we're at such a high latitude, we had very dark winters.
29:27These conifers are in the same bed as the hadrosaurs, and there are no other plants associated.
29:33There are no flowering plants, no angiosperms, only this dominance of conifers.
29:38It's clear that the hadrosaurs had to be eating the conifers, and this is how they survive throughout the year, especially during the winter as well.
29:47This right here is what I've been looking for.
29:50It's a little bit gray.
29:51It's a light gray color when it's weathering, but you see when it's fresh, it's very dark, and it's full of organic material.
29:58A lot of plant material.
29:59Well, what are those light colored pieces?
30:01Oh, look at this.
30:02Here's a piece of a hadrosaur.
30:03Hey!
30:04That's a hadrosaur.
30:05Wow!
30:06A hadrosaur toe bone.
30:07Oh, that's fantastic.
30:08Spectacular preservation.
30:09You see how good that is?
30:10What we're dealing with here is really history.
30:13It's almost as if somebody had put together in a book the history of some point on this ancient Alaskan landscape.
30:22So at this, down here in our book, all the pages are in the form of layers of mud that are coming in, probably with seasonal floods from the neighboring river.
30:33And those, during that time, mostly plant debris, mostly conifer needles was accumulating.
30:41As we move later in time, and these deposits thicken up, this is no longer just sort of accumulating mud and leaf litter.
30:50It's almost a swampy area, a little back swamp away from the main channel in which there was a great deal of organic material accumulating.
31:00Almost a coal, if there was more organic material, this would almost be a coal.
31:05But this is the environment where the dinosaur bones were sweeping in.
31:09Now this also has conifer needles in it, but they're not as concentrated as the conifer needles in the other deposits,
31:19and they're harder to see because it's against a very, very dark background.
31:23So the basic vegetation was the same, but this is a, at this point in the history of this one spot that we're standing on,
31:31now dinosaur bones were washing into this site.
31:34The dinosaur discovered in Alaska is a plant-eating hadrosaur called Edmontosaurus,
31:44which first appeared around the mid-Cretaceous.
31:50Fossils of Edmontosaurus have surfaced in locations across North America.
31:56This dinosaur, it seems, filled the evolutionary niche left by the larger sauropods.
32:07Edmontosaurus was a duck-billed dinosaur, about half the size of the Barosaurus.
32:14Why had this animal traveled so far north?
32:22The answer, according to Dr. Taggart, may lie with the plant fossils discovered near Edmontosaurus.
32:29The plants that are preserved in the rocks are the same kind of conifers that we find in the stomachs of dinosaur mummies from Alberta,
32:41mummified dinosaurs from Wyoming.
32:44Clearly the dinosaurs up here must have been preferentially eating this kind of vegetation.
32:51Now the fascinating thing is that if they were as selective every place else in the world,
32:57when this big change in plants was taking place,
33:00and the flowering plants were basically displacing the conifers almost every place else in the world,
33:06if they continued to be as selective as they must have been up here on the Arctic slope of Alaska,
33:11then dinosaur populations worldwide were in very, very serious trouble.
33:21During the Cretaceous, angiosperms from warm equatorial countries
33:26prospered everywhere, while conifers were dominant only in polar regions.
33:31Without an ample food supply, Edmontosaurus was forced to migrate from its temperate home
33:45toward conifers in the Arctic reaches.
33:48For the large-bodied dinosaurs, the days of bounty had drawn to a close.
33:55Alberta, Canada.
33:57In this strangely sculpted landscape, the final chapters of the dinosaur age unfold.
34:03The Red Deer River, also known as the River of Time.
34:10The layers of sediment lining its banks date from the last hundred million years
34:12of the time.
34:13Alberta, Canada.
34:14Alberta, Canada.
34:15Alberta, Canada.
34:16Alberta, Canada.
34:17In this strangely sculpted landscape, the final chapters of the dinosaur age unfold.
34:20The Red Deer River, also known as the River of Time.
34:26The layers of sediment lining its banks date from the last hundred million years of the dinosaur.
34:35From this region came fossils of a new type of plant-eating dinosaur.
34:47This three-horned dinosaur, Triceratops, was one of the ceratopsians or horn-faced dinosaurs
34:54that dominated the late Cretaceous era.
35:00Heavily armored and somewhat resembling today's rhinoceros, Triceratops measured thirty feet long
35:06and weighed up to six tons.
35:12But on the evolutionary ladder, this creature never reached the status of its predecessor,
35:17Berosaurus.
35:21From what we understand about this group of animals, they were of relatively low stature.
35:28Kind of a grazing animal in large herds, very much like cattle.
35:34Everything that we can see suggests that they browsed and fed off of low vegetation.
35:41And towards the end of the Mesozoic, during the Cretaceous, the lowest vegetation would be
35:45probably towards the end of the Cretaceous angiosperms.
35:50The ceratopians, probably just ate and ate and ate, migrating over their habitat as they
36:00remove the food from one location, moving on to another.
36:04With its three menacing horns, even the most formidable predators steered clear of the Triceratops
36:15as it foraged for food.
36:21But what distinguishes Triceratops in the historical record was its ability to adapt where others
36:32couldn't.
36:36At last, a dinosaur that could feed on flowering plants and grasses.
36:48In this landscape full of life, it is hard to imagine that the dinosaur age was fading.
36:55Meanwhile, in the shadow of the prospering Triceratops, angiosperms had begun to seek new partners in evolution.
37:11On a Cretaceous night, mammals, our ancestors, came alive at the foot of the sleeping Triceratops.
37:22The earliest mammals were small, about the size of a mouse.
37:27Still only bit players in Earth's evolutionary drama, these tiny animals moved about at night to avoid predators.
37:38Almost all mammals until then had fed on insects.
37:41But as angiosperms gained more ground, mammals expanded their diet.
37:47As a result of this change, flowering plants were dispersed to an even larger domain.
37:56Summer in Hokkaido, the northernmost island in Japan.
38:03The season when sweetbriar blossom over the countryside.
38:08Sweetbriar are relatives of the planet's early fruit-bearing plants.
38:17By responding quickly to evolutionary pressures, angiosperms won the cooperation of other species.
38:25Their first triumph, attracting insects who would distribute their seed.
38:37Now, with the advent of fruit-bearing plants, came new partners in evolution. Mammals.
38:50Mammals disperse the fruit seeds to places they may never have reached otherwise.
38:57Both plants and animals benefited from this exchange.
39:02Ecologist Dr. Yumoto of Japan's Kobe University has been conducting field research in Southeast Asia and Africa to study how plants and animals interact.
39:21Yumoto has observed the symbiotic connection between flowering plants and mammals in tropical rainforests.
39:34Small fruit consumed by small animals like squirrels.
39:40Large fruit.
39:41Large fruit that attracts monkeys and chimpanzees.
39:46Co-evolution to meet specific needs.
39:50As life becomes more complex, flowering plants and animals develop more exclusive relationships with one another.
39:59As large as a football, this giant fruit is a treat for the modern elephant.
40:08But if elephants can feast on angiosperms, why not other large creatures like dinosaurs?
40:14If dinosaurs had formed a symbiosis with plants, by spreading seeds and contributing to their reproductive process,
40:26then plants would certainly have made an adaptive effort to create large fruits to have their seeds dispersed more efficiently by them.
40:33But there is no evidence from existing fossils, either of plants or dinosaurs, that indicate there was ever a plant that benefited from such a relationship with dinosaurs.
40:45So, as angiosperms established an intimate relationship with mammals, or as the close interaction emerged between angiosperms and insects, their pollen agent,
40:56their pollen agent.
40:57There is a good possibility that dinosaurs were left out of the game and lost footing in the ecological system.
41:10Without enough food, the planet's remaining dinosaurs would slowly die out.
41:19And their 160 million year reign finally come to an end.
41:25Despite lifetimes of research by paleontologists, no one knows the exact cause of the dinosaur's mass extinction at the end of the Cretaceous period.
41:44But it's now thought that most dinosaurs were in decline at the time of a cosmic collision 65 million years ago.
41:54A comet, or asteroid, six miles wide, struck the Earth with the force of 100 million megatons.
42:01The impact created a worldwide firestorm and hurled a cloud of dust and debris into the atmosphere, blocking out the sun.
42:22For many seasons, the planet appeared lifeless.
42:29In this never-ending winter, plant life vanished, and with it, plant eaters and their predators.
42:36The dinosaurs could not withstand this final blow.
42:43In this never-ending winter, plant life vanished, and with it, plant eaters and their predators.
42:50The dinosaurs could not withstand this final blow.
42:57The dinosaurs could not withstand this final blow.
43:05But enough plants and animals managed to survive this age of darkness.
43:20Mammals that for millions of years had lived in the shadow of the dinosaur could fill the evolutionary niches left behind.
43:32At last, winter subsided, giving way to sunlight and fresh signs of life.
43:47With the demise of the dinosaurs, mammals flourished in every corner of the globe.
44:05The Earth found a new rhythm.
44:16And an evolutionary dance with different partners had begun.
44:26Versatile creatures would appear.
44:29Animals that could climb, or run, or forage skillfully in their new habitat.
44:35The first of a long line.
44:39A lineage that would one day include the family of man.
44:45All owe their existence, in some measure, to a cooperative relationship with plants.
44:59We may never fully understand why dinosaurs disappeared from the planet,
45:05while their fellow species, flowering plants, insects, and mammals, flourished.
45:12Larger than life, dinosaurs may have been victimized by their size.
45:17The very trait that assured their sovereignty for 160 million years.
45:22In a twist of fate, dinosaurs, unable to change with their environment,
45:30were driven to extinction, not by a predator, but by the most powerful and random force of all.
45:37The force of nature.
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