La Plus Grande Créature Unicellulaire Du Monde

Sympa

La plus grande créature unicellulaire du monde est vraiment impressionnante ! Il s'agit d'un organisme appelé xénophyophore, et ce n'est pas une blague. Ces méchants garçons peuvent atteindre une taille de 10 cm, ce qui peut paraître anodin, mais pour une cellule unique, c'est énorme ! Elles vivent dans les profondeurs de l'océan, où elles engloutissent toutes sortes de particules minuscules qui flottent autour d'elles. Alors oui, la prochaine fois que vous nagerez dans l'océan, n'oubliez pas qu'une créature unicellulaire géante pourrait se cacher sous vos pieds !  Animation créée par Sympa. ---------------------------------------------------------------------------------------- Musique par Epidemic Sound https://www.epidemicsound.com   Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna​ ---------------------------------------------------------------------------------------- Nos réseaux sociaux : Facebook: https://www.facebook.com/sympasympacom/ Instagram: https://www.instagram.com/sympa.officiel/  Stock de fichiers (photos, vidéos et autres): https://www.depositphotos.com https://www.shutterstock.com https://www.eastnews.ru ----------------------------------------------------------------------------------------  Si tu en veux encore plus, fais un tour ici:  http://sympa-sympa.com

Transcript

00:00These strange spots are not just ice balls in the ocean.

00:04They are some of the largest organisms,

00:07a unique cell that you will find on Earth.

00:09And they burst, if you press them.

00:12We are interested here in a particular type of algae

00:15that can reach the size of a pinhead or an ocular globe,

00:19an eye of a sailor, as they are called in some countries.

00:23The size of the algae depends on what is in its vacuole,

00:26i.e. the space located inside its cellular wall.

00:30This organism is made up of a single cell,

00:33but it can have more than one nucleus.

00:35It is as if it had several control centers in its cell.

00:39The reason is that these organisms are choenocytic.

00:42This means that they are made up of a set of nucleuses

00:46without a separating wall.

00:47And they are not mythical creatures

00:49hidden at the bottom of the Mariana Falls.

00:51Divers from around the world,

00:53exploring the coral reefs,

00:55can come across these organisms.

00:57These algae are of different colors,

00:58black, bright green or silver.

01:01Their color depends on the structure of their cellular wall.

01:04It happened that researchers came across a sparkling orb

01:07that looked like a golden egg at the bottom of the ocean.

01:10What is interesting is that this egg was pierced with a hole.

01:14The question was therefore to know

01:15if something had tried to come out or enter this orb,

01:19or if it was just a small gelatinous mass

01:21left to itself on the ocean floor.

01:24Normally, the cells do not become so large.

01:27This would disturb their balance.

01:29If something is too large,

01:31the relationship between the surface and the volume is no longer optimal.

01:34But these marine algae

01:35have a great trick to achieve such a size.

01:39They are made up of different parts,

01:41each with its own chloroplasts and its own nucleus.

01:45If you pressed very hard on one of these jelly balls,

01:48it would not burst like a balloon.

01:51It would burst upwards,

01:52and it would probably put up with it,

01:54because a single nucleus is enough for a new globe to develop.

01:58Keeping them in an aquarium is therefore not an easy thing.

02:00And then they live much more peacefully at the bottom of the ocean,

02:03where no one comes to bother them.

02:06The question that arises now is the following.

02:09If a cell can reach such a size,

02:11what size can real living beings reach?

02:14The biggest animal that has ever walked on our planet

02:17was probably a dinosaur called Argentinosaurus,

02:21a giant that lived about 90 million years ago.

02:25We can compare it to the heaviest terrestrial creature we know today,

02:30the African elephant.

02:31It weighs less than 7 tons.

02:33Gigantic for us,

02:34it would look like an insect next to the Argentinosaurus,

02:37which weighed about 77 tons.

02:39And they both look small next to the blue whale,

02:42which weighs 165 tons.

02:44It is probably the heaviest animal that has ever lived on Earth.

02:48In theory, and according to the laws of physics,

02:51creatures living on Earth can weigh up to 120 tons.

02:55There is a mathematical principle,

02:58the law of squares and cubes of Galilee,

03:00which explains why animals cannot grow indefinitely.

03:05According to him,

03:06the ratio of two volumes is greater than the ratio of their surface.

03:09This means that when a creature grows,

03:12all its parts do not grow at the same rate.

03:16If the elephant becomes three times larger,

03:18taller and longer,

03:19its overall size will also increase.

03:22But its mass will increase much more than that.

03:24This means that the volume will increase more quickly

03:27than the surface of the animal's body.

03:28This is why the biggest animals

03:30need much larger limbs to support their weight.

03:34The problem is that these limbs are generally not strong enough

03:37to support such a mass.

03:39The only way for our gigantic imaginary elephant

03:42to move such a heavy body

03:44is to have extremely large and thick legs,

03:46if only to walk, to run.

03:49Let's not even talk about it.

03:51Physics is not the only one responsible for size limits,

03:54even if thanks to it,

03:56no animals over 100 tons walk in our gardens.

03:59Another important element is the amount of food,

04:02because these giants would certainly need a lot of reserves.

04:06But it's not just about quantity, of course.

04:09Creatures can only grow

04:11if they live in suitable environments,

04:14with high-quality and rich in nutrients.

04:18This probably explains why some reptiles,

04:21such as the titanosaurs,

04:23have become much bigger

04:25than, for example, the largest mammals

04:27that crossed our land.

04:29Hot-blooded mammals have a faster metabolism.

04:33This means that they need about ten times more food

04:36than reptiles to maintain their size.

04:38Reptiles not only have a rather slow metabolism,

04:41but also a very low body temperature,

04:43which allows them to eat less without starving.

04:46And then they also grow

04:48because they don't burn their calories so quickly.

04:51No wonder the largest dinosaurs

04:53were ten times larger than the largest mammals.

04:56Blue whales are a kind of exception to all these rules.

05:00They are hot-blooded mammals.

05:02But when you live in the ocean,

05:04being a giant is not a big problem.

05:07It is easier to be very big in the water,

05:09because the bones and muscles

05:11suffer less stress and pressure,

05:13which terrestrial animals cannot avoid.

05:16Thus, blue whales can swim

05:18and look for food all day long.

05:21They just have to open their mouths

05:23to let in large quantities of plankton.

05:26So yes, our planet has proven

05:28that it could welcome gigantic creatures

05:30for hundreds of millions of years.

05:32Some of them even walked on land

05:35and not only swam in the ocean.

05:37But over the last 20,000 years,

05:39most of them have disappeared.

05:41Large terrestrial mammals,

05:43such as rhinoceros and elephants,

05:45no longer exist in certain parts of the world

05:48and their number is decreasing.

05:50Whales are also less numerous.

05:52For giant animals to evolve again to this point,

05:55man would have to withdraw.

05:58If there are no more gigantic dinosaurs,

06:00some creatures present on our planet today

06:04are still surprisingly and dangerously large.

06:07Like the marine crocodile,

06:09the largest reptile in the world.

06:11A male can reach 7 meters

06:13and weigh about 1,000 kilos.

06:15And that's not the only scary thing about them.

06:17They have the second bite,

06:19the most powerful on the planet,

06:21just behind the crocodile of the Nile.

06:23The title of the largest bird on the planet

06:25comes back to the ostrich.

06:27It has wings, but they are too short to fly.

06:30The animal holds them tight when it runs,

06:32which allows it to maintain its balance.

06:34And then its body is too big for flight anyway.

06:37That's why evolution had to give them another advantage,

06:40that of being able to run very fast.

06:43Do not oppose an ostrich

06:45if you cannot run at more than 64 km per hour

06:48over short distances

06:50or at least 48 km per hour over long distances.

06:53In one go,

06:55this bird can travel up to 5 meters,

06:57which is the length of a medium-sized family car.

07:00Do not underestimate these creatures

07:02simply because they are birds.

07:04They have very powerful legs

07:06and they know how to use them.

07:08They can kick

07:10with a force that would even terrify a lion.

07:13We would not expect

07:15turtles to become so big

07:17and look so mean,

07:19but the alligator turtles

07:21still manage to surprise us.

07:23With their beak-shaped jaws,

07:25their iris-shaped carapace

07:27and their thick,

07:29scaly eyes,

07:31they look like strange carapace dinosaurs

07:34or the great enemies of Mario and Luigi.

07:37They like to spend their time in lakes,

07:39rivers and canals

07:41in the southeast of the United States

07:43and live up to 100 years.

07:45They have chemosensory organs

07:47located in their neck,

07:49which means they can feel

07:51with their throat.

07:53This is very useful to them

07:55because their eyes do not serve them much

07:57so they breathe water into their throat

07:59according to a specific method

08:01called gular pumping

08:03and thus take samples

08:05that they can then analyze.

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