- 4 months ago
see more on:
https://realtv.mytvchannel.org/index.html
https://realtv.mytvchannel.org/index.html
Category
📚
LearningTranscript
00:00.
00:30There are some four million different kinds of animals and plants in the world.
00:55Four million different solutions to the problems of staying alive.
00:59This is the story of how a few of them came to be as they are.
01:29The South American rainforest, the richest and most varied assemblage of life in the world.
01:54Those are howler monkeys up there.
01:56There are around 50 different kinds of monkeys in these forests.
02:01Some of the most beautiful creatures here are hummingbirds.
02:04Fifty-four different kinds have been found within a few miles of where I'm standing,
02:09and over 300 have been found in South America as a whole.
02:13In fact, nobody knows exactly how many different kinds of animals there are here.
02:17Wherever you look, there's life.
02:33There are several hundred thousand different insects that have been named,
02:37and without doubt, many hundreds more that haven't.
02:40And all these varied creatures and plants form one complex mosaic.
02:51The orchid needs the bee to pollinate it.
02:54The anteater couldn't have existed before the ants,
03:00so unless the whole complex was brought into existence in one flash of instant creation,
03:05different organisms must have appeared at different times.
03:08But which came first, and why should there be such an immense variety?
03:12Such questions obsessed a young 24-year-old Englishman who came to these forests in 1832.
03:22His name was Charles Darwin,
03:24and he was enthralled almost to the point of ecstasy by the richness of life that he found here.
03:31In one day, in a small area, he discovered 69 different species of beetle.
03:38As he wrote in his journal,
03:41it's enough to disturb the composure of the entomologist's mind
03:45to contemplate the future dimension of a complete catalogue.
03:51The conventional view of the time was that each and every species of animal and plant
03:57had been individually created by God,
04:01and Darwin was no atheist.
04:08During the next three years, the beagle sailed around South America
04:11and up into the Pacific.
04:16600 miles west of Ecuador,
04:19they came to the lonely Galapagos Islands.
04:21It was here on these volcanic islands
04:44that Darwin's doubts and puzzles about the creation of species were reawakened.
04:51It was here on the island of the Pacific.
04:53It was here on the island of the Pacific.
04:54It was here on the island of the Pacific.
04:55It was here on the island of the Pacific.
04:56It was here on the island of the Pacific.
05:01Everywhere, Darwin found creatures that bore a general resemblance
05:05to those that he had seen on the mainland.
05:10But nearly all were slightly different.
05:15These, for example, were, without doubt, cormones,
05:18birds,
05:20similar to those that he had seen flying along Brazilian rivers.
05:23But here in the Galapagos,
05:25their wings were so small and with such stunted feathers
05:28that the birds had lost their powers of flight.
05:34And these were clearly iguanas.
05:36He had seen such creatures climbing trees and eating leaves
05:39in the South American forests.
05:41But here on the Galapagos, where there was little vegetation,
05:44these iguanas fed on seaweed.
05:46And they were not the same.
05:48Smaller, darker, and with unusually long claws
05:51to help them keep a foothold among the crashing breakers.
05:54They also had extraordinary habits,
05:55swimming fearlessly out to sea and diving deep to graze on the seabed.
06:09The Galapagos Islands got their name from the herds of tortoises that live on them,
06:28and which sailors for centuries had slaughtered for food.
06:32But these two were very obviously different from any mainland tortoise.
06:36They were many, many times bigger.
06:39The English vice-governor of the islands told Darwin
06:43that he could tell without difficulty
06:45which island a particular tortoise came from by its shape.
06:53This one, for example, with its deep rounded shell,
06:56comes from a well-watered island
06:58where it can feed mainly on vegetation on the ground.
07:06This one, on the other hand,
07:07has a peak to the front of its shell
07:09that enables it to stretch its long neck upwards.
07:13It comes from an arid island
07:14where the tortoises often have to crane up
07:16to reach the only food available,
07:18the branches of trees and cactus.
07:21The suspicion grew in Darwin's mind
07:23that species were not fixed forever.
07:25Perhaps these tortoises were all descended from common ancestors
07:29and had changed to suit their particular islands.
07:35The differences that Darwin had noticed amongst these Galapagos animals
07:40were, of course, all tiny.
07:42But if they could develop,
07:44wasn't it possible that over the thousands or millions of years
07:47a whole series of such differences
07:49might add up to one revolutionary change?
07:53Was it not possible, perhaps,
07:54that in the past amphibians had developed watertight skins
07:58and so turned into reptiles?
08:00Or that a lizard-like reptile
08:02had developed a feathery kind of scale
08:04and so become a bird?
08:06And even that man himself
08:08might be descended from a group of tree-swinging apes?
08:12In truth, the idea was not a new one.
08:16Other people before Darwin had suggested
08:18that all life on Earth might have a common ancestry.
08:21But Darwin went further.
08:23He gave the idea irresistible force
08:25by suggesting a mechanism
08:27which might have brought that about.
08:29He called the mechanism natural selection.
08:32Put briefly, his argument was this.
08:37Individuals of the same species
08:39are not absolutely identical.
08:42Some of these giant tortoise hatchlings
08:45may have, from birth,
08:46slightly longer necks than others.
08:48In times of drought,
08:50they will be able to reach leaves and live
08:52while the shorter-necked ones die.
08:57So those best fitted for the environment
08:59will transmit their characteristics
09:01to their offspring.
09:03After countless generations,
09:04the tortoises on arid islands
09:06will have longer necks
09:08than those on well-watered ones.
09:10And so one species
09:11will have given rise to another.
09:19In these programmes,
09:20we're going to survey
09:22the unmeasurable variety of animals
09:25that have been produced by natural selection
09:27and look at them not as isolated oddities,
09:30but as elements in a long and continuing story
09:33that began a thousand million years ago
09:35and is still continuing today.
09:38Some creatures, the mammals,
09:39such as these sea lions and myself,
09:42mammals both,
09:43are relatively recent arrivals on the scene.
09:47Others, the birds, the reptiles,
09:49the amphibians, the fish,
09:50have been here long, longer than we have.
09:53In places where conditions have remained virtually unchanged
09:57over immense periods of time,
09:59there are still creatures living
10:00which resemble very closely their early ancestors.
10:04They can tell us a lot.
10:06But in order to disentangle the story,
10:08we shall also have to look for evidence in the rocks.
10:12The bodies of animals falling to the bottom
10:23of ancient seas and swamps
10:25sometimes get entombed in the accumulating sediment.
10:28When, after millions of years,
10:30those sediments turn to rock,
10:32those remains of animals and plants survive as fossils.
10:36Since the discovery of radioactivity,
11:02scientists have developed techniques
11:04of measuring the age of rocks
11:06based on the rates at which some chemical elements decay.
11:09So fossils can be dated to within a few million years.
11:13But there are much simpler ways than that
11:15of establishing the comparative ages of rocks
11:18that anyone can use.
11:19And there is no more dramatic place to do so
11:22than in the Grand Canyon in the American West.
11:34The Colorado River, aided by wind and rain,
11:43has cut a gigantic section
11:45through the sandstones and limestones of Arizona.
11:48The layers still lie largely undisturbed,
11:51so obviously the lower ones
11:53must have been deposited before the upper ones.
11:55So if we want to trace the ancestry of life
11:57back to its beginnings in this part of the world,
12:00we have to go deeper and deeper into the canyon.
12:16This is the greatest gash that exists
12:18in the surface of the earth.
12:20From the rim to the river at the bottom
12:22is a vertical mile.
12:24There are a number of trails down
12:26and the usual way is to make the trip
12:28on the back of a mule.
12:54Here we're about 500 feet below the lip of the canyon,
13:17and already the rocks are about 200 million years old.
13:21There are no mammal fossils to be found here,
13:24but there are some four-legged land animals still.
13:27Small reptiles, a little lizard-like creature
13:30that has left its tracks along here,
13:33which was once the face of a sand dune.
13:36Farther down, there are no signs whatever of any reptiles,
13:53but in limestones 400 million years old,
13:56the bones of strange armoured fish have been found.
13:59The trail winds on through rocks formed on the bottom of ancient seas.
14:11With every 20 feet we descend,
14:13we go back a further million years.
14:30The Grand Canyon is really two canyons,
14:32one inside the other.
14:34For a while, the trail flattens out
14:36as it approaches the rim of the inner canyon.
14:42And here I'm about two-thirds of the way down,
14:45say about 3,500 feet below the rim.
14:49And the rocks here are about 500 million years old.
14:54These rocks have no backbone animals in them at all, no fish.
14:59The only creatures there are are creatures without backbones,
15:02including a whole lot of worms,
15:04which have left this delicate tracery of trails
15:08in what was mud on the bottom of a shallow sea.
15:12At last, the bottom and the Colorado River.
15:38It's taken nearly a day, going fairly easily, to get this far.
15:42We've ridden some seven miles of trail
15:45and have descended that vertical mile into the Earth's crust.
15:53The rocks here are getting on for 2,000 million years old.
15:59And for the past 700 or 800 feet of our descent,
16:02they've had no signs of any fossils at all in them.
16:05For many years, it was thought that all rocks of this great age
16:09were without any fossils.
16:11Why was this?
16:12Was it because they were so unimaginably old
16:15that they'd had all traces of life crushed from them?
16:18Or did life really begin with creatures as big as a worm?
16:22For many years, this was a great puzzle.
16:25And then, about 20 or 30 years ago,
16:28people realised that they'd been looking in the wrong rocks
16:31and in the wrong way.
16:41These are the right rocks.
16:43They're a kind of flint called chert,
16:46and they're on the shores of Lake Superior in Canada,
16:50about 1,000 miles east and north of the Grand Canyon.
16:54They were well known during the last century
16:56because the pioneers used them in their flintlock guns.
17:01And scientists have recognised too, for a very long time,
17:04that they were extremely ancient rocks.
17:07We now know that they are about the same age
17:10as the rocks in the bottom of the Grand Canyon.
17:12That's to say, about 2,000 million years old.
17:16But these strange rings in them,
17:20for a long time, these were a subject of great controversy.
17:24Some scientists maintained that they were signs of very early life.
17:30Others, that they were no more than the result
17:33of the ordinary chemical processes during the rocks' formation.
17:37But then, during the 1950s,
17:40scientists started looking at them in the right way.
17:50First of all, you have to cut a wafer-thin slice
17:53of the gunflint rock.
17:59This is then ground down still further for several hours
18:02until the slice is translucent.
18:11When scientists first prepared gunflint chert
18:13to look at through the microscope,
18:15many people doubted that primitive forms of life,
18:17even if they existed 2,000 million years ago,
18:20could possibly be preserved as tiny fossils.
18:22And then scientists saw this.
18:29Marks in rocks can be deceptive.
18:34They may just be the result of mineral action.
18:37But these filaments proved to be almost identical
18:40to primitive algae growing today.
18:43The search continued.
18:49Soon, the fossilized remains of many other kinds of primitive life
18:54were found that had once lived in those early seas.
18:58And since those first discoveries,
19:05other microfossils have been found elsewhere
19:08in rocks that are even more ancient,
19:10some over 3,000 million years old.
19:13These immense periods of time baffle the imagination.
19:18But perhaps we can get some idea of the relative lengths
19:22of the various stages if we condense the whole history of life on Earth
19:28into one year.
19:30Then 10 million years become one day.
19:33And on that calendar, I am talking in the very last moment of December the 31st.
19:39And primitive man will have appeared only a few hours ago in the early afternoon.
19:45The first backboned animal will have crawled up onto land during the last week of November.
19:51And these gunflint cherts will have been formed on June the 15th.
19:58Now let's go back way, way to the beginning of January.
20:03To the beginning of life.
20:05Over three and a half thousand million years ago,
20:15our planet was radically different in almost every way
20:18from the one we live on today.
20:25Erupting volcanoes built up islands of lava and ash in the global seas.
20:30The atmosphere was filled with gases such as ammonia, methane, hydrogen and steel.
20:46There was virtually no oxygen.
20:48In consequence, there was no ozone layer in the atmosphere.
20:51So ultraviolet rays, in strengths that would be lethal to us,
20:55bathed the young planet.
21:00The ultraviolet light, together with heat and electricity,
21:28light, together with heat and electrical and radioactive discharges, brought about many
21:33chemical changes in the waters. Complex carbon compounds were formed, including amino acids,
21:39the building blocks of protein. For millions of years, the chemical soup thickened and
21:49changed. Possibly some compounds were added to it from outer space.
21:53Some carbon compounds aggregated in droplets, with a membrane through which other chemicals could pass.
22:14Eventually, unusually large molecules appeared, which had extraordinary characteristics. They
22:20caused amino acids to form around them, and so built proteins, and they could also produce copies
22:26of themselves. Such a molecule, known as DNA, is at the centre of every life cell. Its shape
22:35is a double spiral, linked by chemical units of just four kinds. Their arrangement acts as a code for
22:43the production of proteins, and a group of them in a section of DNA is called a gene.
22:50On occasion, the DNA unzips. Each half then attracts the correct chemical units, and so forms two new
22:57identical molecules. When this first happened, primitive cells formed new cells, and life on earth
23:05had appeared. But sometimes there is a mistake, a mutation. These caused variations in the first cells, and natural
23:18selection sorted them out. Those that were as well or better suited to their environment survived, the rest died.
23:27And so, over tens of millions of years, a variety of bacteria-like organisms developed, thrived, and invaded
23:45new environments on earth. Evolution had truly begun.
23:52We can get a glimpse of what those first stirrings of life were like in the hot volcanic springs of such places
24:10as Yellowstone Park in Wyoming.
24:12And in these springs, staining them a whole variety of colours, they're flourish microorganisms.
24:27Micro-organisms that look to be almost identical with some of the earliest fossils that we know.
24:34Tufts of bacteria grow, where the water is hottest.
24:37In cooler areas, other bacteria deposit silica in strange coloured crusts.
24:51These bacteria represent the next big step, for they are probably very like the first forms
24:57to manufacture food inside their own cell walls, with the help of energy from the sun, light.
25:04One of the raw materials they needed was hydrogen, and at first they got it as sulphuretted hydrogen,
25:14which occurs conveniently enough in volcanic gases. There's some around here. This place smells
25:19a bit of rotten eggs. And indeed, there are such bacteria flourishing in the hot water of these springs.
25:26But then that link with volcanoes was broken. Some forms of bacteria arose, which got their hydrogen
25:35from a much more widespread and easily available source, from water. And that was a crucial stage
25:41in the history of life. Because if you take hydrogen from water, you are left, as a by-product, with oxygen.
25:49These new blue-green bacteria, or cyanophytes, still exist, as slime on wet rocks or in ponds covered
26:04with silver bubbles. It was they that first contributed oxygen in large quantities to the atmosphere.
26:11Under the microscope, you can see that they're very simple structures. Some form chains, others are isolated beads.
26:23On a larger scale, they form mats with bacteria in the cooler springs of Yellowstone.
26:36Some of these blue-greens deposit lime as part of the chemistry of their body processes. And in one place
26:50in the world, here in a bay on the coast of Western Australia, they grow large and huge to form these
26:59great pillars. What makes this place so special is that the mouth of the bay is almost blocked by a
27:06bar of sand covered with seagrass. And this restricts the flow of the tide in and out, with the result
27:13that these waters are extremely salty. And so virtually none of the creatures which eat blue-greens can
27:20survive here. And so these blue-greens, these very primitive organisms, can grow uncropped just as they did
27:29when they were the most advanced form of life 2,000 million years ago, at the beginning of life on Earth.
27:37And here is an explanation for those extraordinary shapes that we saw on the shores of Lake Superior.
27:52This is as close as we may ever get to a scene of the world when life was at last beginning to stir.
28:18Now life had reached a point of no return. The oxygen accumulated and formed a layer of ozone in
28:31the atmosphere, screening off ultraviolet rays, the very source of energy that had helped to create the
28:36first life. So it could never begin in the same way again.
28:47Outwardly, things changed little for hundreds of millions of years. But eventually the state was set
28:54for a new and dramatic step. To find evidence of that development, you need go no further than your local pond.
29:11Most microscopic organisms here are just single cells, yet each is very much more complex than any bacterium.
29:30Some, like this amoeba, seem to have animal characteristics. And some appear to be simple plants.
29:42Yet others seem to be half animal and half plant. In terms of complexity, they are about as different
29:49from a bacterium as a man is from a jellyfish. To see why, we have to look inside one of them with an electron microscope.
29:58The DNA, unlike that in the bacterium, is enclosed in its own compartment. Other parts of the cell resemble
30:06and act like blue greens. These look more like bacteria and are a source of energy.
30:17This particular cell is driven by a tail that resembles yet another type of bacterium.
30:25So it appears that this tiny creature is composed of a committee of smaller ones.
30:30And indeed many people now believe that it was by some form of collaboration between primitive cells
30:36that such organisms came into existence.
30:43But it took a long time for life to reach this stage, probably not until some 1200 million years ago,
30:51say early September in our life on earth year.
30:54These plant cells belong to this new advanced type. Many kinds of them still abound in fresh water and the sea,
31:07and they form the basic food of other simple organisms.
31:19some of them have delicate skeletons of silica.
31:49some of them still abound in fresh water.
31:58This is another kind, with chambered shell of chalk, and so small that several would fit on the head of a pin.
32:09The animals, in essence, are like an amoeba, to which they're closely related.
32:14They catch their food with sticky threads.
32:19When something tangles with them, it's drawn inside and digested in a special compartment.
32:31The cells can reproduce by splitting into two, as bacteria do.
32:35But some cells have more complicated methods of reproduction.
32:46These have temporarily joined, so that they can exchange genes.
32:50Later they will part, and then divide in the normal way.
32:53In other cases, cells shuffle their genes, and then divide in such a way that they produce a very special kind of cell,
33:07with only half the number of genes of the parent.
33:10These special cells are eggs.
33:12Meanwhile, other members of the same species are also producing sex cells with half rations of shuffled genes.
33:24This time, they're quite different in form.
33:28They have tails.
33:30They're sperm cells.
33:32They're chemically attracted to the egg,
33:36and the first one to find it, down there on the bottom, penetrates the wall.
33:49After getting inside, it swims towards the nucleus and unites with it,
33:53so that the full complement of genes is restored.
33:56But now it's in a new combination, different from either parent.
34:03When this mechanism developed, the extent and frequency of variation greatly increased.
34:08As a result, the pace of evolution accelerated.
34:21One of the most successful groups of single cell creatures in this microscopic world are the ciliates.
34:26They're covered with a coat of beating hairs, the cilia, which drive them through the water.
34:32The cilia also create currents which waft tiny particles of food into their gullets.
34:38These particular ciliates are stalked and remain anchored to one spot.
35:05But others are large and mobile and actively hunt for their food.
35:09These ciliates are among the larger single cell creatures, just visible to the naked eye.
35:28Above this size, it seems that the chemical processes inside become difficult and inefficient.
35:34But size can be achieved in a different way, by grouping cells together in an organized colony.
35:44This volvox, almost the size of a pinhead, is composed of hundreds of cells, each with a tiny tail,
35:50but all beating in a coordinated way.
36:00Inside, daughter colonies are formed, and the tiny, delicate globe ruptures to release them.
36:06Eventually, this coordination between cells was taken a stage further.
36:16Sponges appeared.
36:17There are about 5,000 species of sponges in existence today, and in all of them,
36:29the colonial bonds between their constituent cells are remarkably loose.
36:34Individual cells may crawl around over the surface like amoebae.
36:38If a sponge is forced through a fine sieve so that it's completely broken down into separate cells,
36:44they will, if left alone, reorganize themselves to form a new sponge.
36:49And what is more, each kind of cell will take up its proper place.
36:53Some are specialized to form the walls.
36:58Others are pump cells that line the walls of the channels with which the sponge is riddled.
37:04By beating their tiny threads, they create currents drawing in the water through the pores on the sides,
37:10and then pumping it out at the top after the food has been strained off.
37:14The structure is supported by yet other cells which make tiny needles, and these build to form a skeleton.
37:24In the so-called glass sponges, they're made of silica.
37:32Modern science is only some two or three hundred years old, and yet already it's provided us with some
37:38profound insights into the workings of the world around us.
37:42But there's still a very great deal that we don't know.
37:45Take this sponge skeleton, for example.
37:49How on earth did the microscopic sponge cells, one of the most primitive organisms that we know,
37:57collaborate to build out of a million splinters of silica this complex and beautiful structure,
38:05which is sometimes called Venus's flower basket?
38:08Some religious people will maintain that it is the work of God, and that is all that need be said.
38:15Some scientists will claim that it's only a matter of time before we will provide
38:19a very much more detailed explanation than that.
38:22Either way, it remains an awesome and beautiful object.
38:26But sponges, in an evolutionary sense, are a dead end.
38:31They have no two mouth, no gut, no muscles, no nervous system.
38:37But this has.
38:38It's a jelly-like creature with just two layers of cells.
38:47The inner one lines a cavity which has a single opening.
38:51Its design may be simple, but nevertheless it is a fully coordinated, multi-celled animal.
38:58It's one of several kinds of comb jellies, which swarm in the oceans,
39:02but which are so transparent that they're hardly ever noticed.
39:05It's a very powerful object.
39:16To appreciate the full beauty of comb jellies, you have to use special lighting.
39:20They swim with rows of cilia arranged like combs,
39:32and their beating produces interference colours like a rainbow.
39:50This pulsating bell is a close relation of the comb jelly.
40:17Technically, it's called a medusa.
40:19After the unfortunate lady in the Greek myth who had snakes on her head for hair.
40:24Its tentacles have stings for capturing prey.
40:28Once caught, it's transferred to the mouth at the centre.
40:38Comb jellies and medusae both have muscle fibres and a simple nervous system.
40:43But most medusae have a surprise.
40:46They begin their lives in a completely different form, like this.
40:55They look like plants, but they're animals.
40:58Each structure began when a tiny free-swimming creature developed from the fertilised egg of a medusa,
41:04and settled on the bottom of the sea, or a piece of weed.
41:06From it sprouted a tiny branching twig bearing flower-like individuals called polyps.
41:12These filter feed with the aid of beating cilia and grow, putting out more branches with polyps on them.
41:22Each polyp is basically equivalent to a swimming medusa.
41:27In some species, medusae can bud directly off the branch and swim away.
41:31In others, they are born from special vessels.
41:34And they are born from special vessels.
42:09All these Medusae, which are not much bigger than a pinhead, have been produced by a process that involves no sex.
42:29Eventually, they themselves develop sexual cells, which will be released into the sea to produce larvae to begin new colonies of polyps again.
42:39This alternation of generations between sexual and non-sexual methods of reproduction has given these creatures and their relatives great scope for variety.
42:51The larger Medusae carry quantities of jelly in their umbrellas to make them more robust in rough seas.
43:16These are the true jellyfish, and many of them lead the same type of double life, having a stationary polyp phase as well as a swimming one.
43:24There's a surprising variety of types of jellyfish.
43:48Some are able to feed on quite large prey, but this one has elaborate ruffles in which there are many pores for netting microscopic food.
43:57This shallow water species uses pulsating movements to create currents of water that bring it food.
44:25It's an obvious deduction that such simple things as jellyfish appeared very early in the development of life.
44:39But for a long time, there was no actual proof that they did.
44:44After all, proof could only come from the fossil record, and who could suppose that such an insubstantial thing as a jellyfish could be fossilized, let alone survive in rocks from the earliest period?
44:55And then, about 30 years ago, in these sandstones in the Flinders Ranges in southern Australia, which are probably about 650 million years old, people found things like this.
45:10At first, many scientists refused to believe that these faint impressions were the remains of jellyfish.
45:23But by now, enough specimens have been discovered to make quite sure that that indeed is what they are.
45:31What's more, almost a dozen different species have now been discovered.
45:36Such fossils as these reveal that, at a very early period, jellyfish existed in many different forms, just as they do today.
45:53This, though a close relative of the jellyfish, is strictly speaking, not a single creature, but a colony of polyps, one that has gone to sea and assumed much the same structure as a true jellyfish.
46:10Another colony that is built on the same principle is known as the Portuguese man-o'-war.
46:20It has no swimming bell, but instead a bag filled with gas that supports the whole colony.
46:27To avoid drying out and overheating, the colony is able to dip the sail into the water from time to time.
46:34Long tentacles trail behind for lengths of up to 50 metres.
46:48The colony begins with just one founding member, which buds off two lines of other individuals.
46:55They, in turn, bud off others, some specialised for feeding, some for reproduction, and some to catch prey.
47:01As with all jellyfish and their relatives, the tentacles have special stinging cells.
47:09Each contains a coiled barbed tube, which discharges immediately on contact with its prey.
47:18And from the end of each comes a drop of paralysing poison.
47:23Animals like the Portuguese man-o'-war are highly complicated creatures,
47:27and you might think that they're comparatively recent developments in the world of jellyfish.
47:32In fact, one of the fossils from the Flinders Range suggests that such colonies existed 650 million years ago.
47:43The impression in this rock is thought to be from a gas bag of such a colony of polyps,
47:49which was blown inshore and cast up on the sandy beaches
47:52that today form the sandstones of the Flinders Ranges.
48:04And that's not all.
48:06Alongside those jellyfish in the same rocks,
48:09there are the remains of other closely related creatures.
48:13These beautiful impressions are of animals in which the equivalent of the Medusa remained very small
48:21and attached to one another to form a colony.
48:24And we can be pretty sure that this is what that was,
48:28because very similar creatures are alive today
48:31and living once more only about 40 miles away from here in the sea.
48:35These are sea pens.
48:40On either side of the stem are polyps which are specialised for feeding and reproduction.
48:46This living one bears a remarkable resemblance to the fossil.
48:58They were given the name sea pen when people wrote with quills,
49:02and apt it must have seemed, for the skeleton is flexible and horny.
49:11They belong to a group called the soft corals.
49:14This is another kind, a soft, flabby organism rather ghoulishly known as dead man's fingers.
49:26Soft corals of one kind or another can grow in depths of up to 6,000 metres.
49:31But stony corals, the ones which produce limestone skeletons and form reefs,
49:37can live no deeper than 40 metres.
49:44The coral polyps live only on the surface of these structures,
49:48each in its tiny limestone cell,
49:51and connected to its neighbours by thin strands,
49:54so that the whole skin is a living network.
49:56As new ones sprout from the connecting branches,
49:59they secrete cells for themselves,
50:01which grow over the early ones and stifle them.
50:08The coral tissues contain plants,
50:12tiny, single-celled green algae.
50:15Like all plants, they release oxygen,
50:18which helps the coral polyps to respire.
50:20They also assimilate carbon dioxide,
50:23taking it from the water,
50:24and that helps the corals to form their gigantic skeletons of lime.
50:37Each species branches and buds in a different way,
50:41and so the colony produces its own individual shape.
50:45Maybe they need to know their own betterå–„ species.
50:51What?
50:52Maybe you have a genius of their innerhalb of terms for you.
50:56If you place it in a proper synthesizer or know the name,
50:59you might be able to prepare them to manifest your belief.
51:05Yep.
51:05The reef may look like some fantastic multi-coloured jungle of plants and flowers,
51:34but when you touch one, it has the hard, incongruous scratch of stone.
52:04The coral organisms are tiny and simple, and yet they grow on such a scale and their stony skeletons are so durable that they may well have been the first science of life that could be detected from outer space.
52:21Certainly this great barrier reef can be seen from the moon, so it may well be that if a passing astronaut came this way several hundred million years ago,
52:32he might have noticed in the deep blue seas of the earth a few mysterious beautiful shapes in turquoise and guessed that life on earth had really started.
52:45ORCHESTRA PLAYS
52:57ORCHESTRA PLAYS
53:09ORGAN PLAYS
53:39ORGAN PLAYS
54:09ORGAN PLAYS
54:14ORGAN PLAYS
54:19ORGAN PLAYS
Be the first to comment