The Evolution of Vertebrates

foreign stalked by animal careers Kaya tiny worm-like creature somehow escaped Extinction this bit of an animal had no protective shell or defensive spines but in the Cambrian Period one part of its design was wholly unique as Conway Morris discovered picaya has a structure remarkably similar to a modern day animal called amphioxus both are equipped with a long stiff Rod running the length of the body the notochord the notochord which supported bakaya's muscle structure is the design common to all vertebrates this modest creature may be our earliest recognizable ancestor picaya I believe evolved into something like a fish and from the fish of course we have the amphibians represented today by the frogs and the salamanders for instance which invaded land in the devonian and then after that we have the reptiles and the mammals so perhaps if pikaya had not survived if it had gone extinct at some time then of course ultimately there would have been no mammals and of course no humans [Music] though much about our lineage remains a mystery the origins of the human backbone are linked to picaya and its notochord [Music] few developments would lead to Greater diversity the reign of animal Keras was not short-lived flourished for nearly 20 million years a hundred times longer than the entire history of homo sapiens but in the evolutionary Lottery it was the lowly picaya that survived bearing offspring that would eventually populate the Seas the land and the skies foreign [Music] foreign [Music] 's Death Valley one of the most arid regions in the world 400 million years ago an enormous river filled this Valley linking it to the distant scene it was here that the fossils of the first fish to Brave the freshwater habitat were found it had taken them 60 million years to gain access to these estuaries the man who discovered the fossil was Dr David Elliott of Northern Arizona University a specialist on Ancient fish the rocks have been slid tons of Earth and sand formed sediments at this site deposited by the river that ran through Death Valley eons ago and it is here that Dr Elliott has been focusing his excavation and research work on Ancient freshwater pioneers tell what that is this is a taraspid this is a lingelid and lingile is rather interesting because they're characteristic of estuarine environments that is environments in which fresh water and Marine waters are mingling those are these are areas of very high nutrients where you may have large numbers of organisms coming to feed and we have many terasbids here um there are also areas that many marine organisms can't get into they're not able to survive in brackish conditions and so it may be that taraspids were protected from some of their possible Predators by living in these environments freshwater habitats have almost no salt content change in salinity can spell instant death for unacclimated marine life this paramecium thrives in the salty medium of seawater breathing saline fluid it regulates its mineral levels and ejects wastes salt free water is added changing the balance in this unfamiliar hostile freshwater environment the paramecium takes in water without voiding it destroying the cell the now bloated paramecium ruptures and Dives taraspas is about eight inches long its head covered with tough bony armor and its body with primitive scales unlike paramecium taraspus managed to adjust to this new fresh water habitat with a little creative bioengineering [Music] the taraspids protective shell prevented water from penetrating the body through its outer layers but the gills it used to breathe were a weak spot [Music] to balance its system taraspus developed a kidney powerful enough to pump extraneous water from its bloodstream [Music] [Music] transforming its physiology was a major evolutionary breakthrough for the first freshwater fish but it was only a first step [Music] 400 million years ago life on the river was unfolding [Music] but the fresh water habitat posed new challenges rapid currents and waterfalls to negotiate [Music] millions of years for marine life to adapt to these new ecosystems to survive here Earth's first fish would experiment with many anatomical designs the gwasha park lies on Northeastern Canada's gaspé peninsula 400 million years ago this was a tropical region situated directly under the equator [Music] etched in this Meandering stretch of cliffs is the 20 million year history of fish evolution fossils of freshwater pioneers fish with fins to resist River current ivorous fish with jaws and teeth there's some layers to Peculiar fish entirely different from any of the others this fish had a backbone until now there were fish with tough exoskeletons but none with hard bone inside the body Cairo lepus the earliest creature with a spine appeared 390 million years ago the most common fish today the Bony fishes are its direct descendants [Music] foreign like modern fish carolepis was equipped with one pair each of pelvic and pectoral fins [Music] it was Sleek with jaws and sharp teeth for catching prey acquiring the spine Cairo lapis developed strong muscles to swim with speed and Power but there were other agile swimmers in the river that had managed to do without one [Music] why then did the backbone develop while the sea was rich in minerals essential to life the river was in short supply this is heart tissue working in unison these cells allow the heart to pump blood throughout the body to function properly the heart needs calcium calcium concentration in a river is in Perpetual flux [Music] when levels are high calcium is stored as bone when they're low the bone Reservoir supplies the necessary mineral regardless of external conditions and while seemingly solid bone is constantly being replenished the top of the screen hard bone is visible moving below are cells that dissolve it [Music] once the bone is dissolved calcium circulates through the bloodstream to every part of the body fate of ancient fish rests on a simple backbone those without eventually perished from Calcium deficiency or returned to their native sea for many years Cairo lepis reigned as the king of freshwater fish his Anatomy gained him independence from the Marine World [Music] today the descendants of cairolepis thrive in both fresh and saltwater habitats [Music] the river was a Proving Ground for the earliest fish on their offspring and in this new habitat they gradually adapted the body system's key to survival on land [Music] another fish with a backbone appeared on the river at about the time of Carol lepus it's called use the noptera a bottom dweller eustanopteron was not an efficient swimmer like many fish but it had secured an evolutionary niche powerful bony fins to push its way through the river's undergrowth this fish was a stealthy Hunter poised for action [Music] houstonopteron's habitat shaped its unusual bone structure which would one day lead to the evolution of terrestrial animals South America's Amazon breeds Acres of jungle swampland mimicking conditions in the age of Youth thanopterod and with the swamps a host of unusual life forms among them the lungfish a mud-dwelling creature [Music] this fish has gills but it also has lungs for breathing air in such murky water oxygen content is often very low the lungfish probably developed lungs to breathe oxygen from the air when the supply in the water was depleted [Music] just as his ancestor eustanopteron had done eons before poking its head above the surface for a life-sustaining breath use thanopteron surely caught a glimpse of the world above the water line now that fish had evolved kidneys bone and lungs land was almost within reach [Music] first four-legged creature appeared 10 million years after eustenoptera its remains discovered in a forest in Scotland [Music] at the time this region resembled today's Amazonian swampland Dr Pear Eric alberg of the British natural history museum has been studying the earliest tetrapods he's trying to find out how and why limbs evolved from fins [Music] only 10 fossil pieces have been discovered to date even from these few specimens an image of this new creature is emerging almost five feet long it looks like today's giant salamander I suspect that the reason why limbs evolved was because these animals were living in very shallow water and limbs can be rather better than fins for moving in those sort of conditions even if you're not really moving on to land these earliest tetrapods with limbs rather than paired fins still have gills Tail Fins and other features which suggest that they were very much aquatic animals so I don't really believe that they were using the lace for walking purposefully over land they might have made short excursions Overland but more probably they were using those limbs in shallow water today's giant salamander still spends most of its time in the water negotiating the shallows is a matter of walking not swimming even in Swift currents the salamander plants its feet on the river bottom and moves around with ease aided by its natural buoyancy to move as fluidly on land the salamander would require a far sturdier skeletal structure [Music] 160 million years ago the ones Barren Earth lay Under The Canopy of green giant forests thrived small insects now burrowed in the Shady wetlands and soil this landscape was ready to support New Life but to take their first step on land our ancestors had one more obstacle to overcome gravity [Music] this is ichthyostega an animal that surfaced 10 million years after the earliest four-legged creatures [Music] judging from the size of his skull ichthyostega measured nearly four feet long its backbone and hind legs clearly defined but this animal also had thick finger bones and a sturdy skeletal structure scientists conclude this was the first creature to walk on land first time an animal with a supporting skeleton around its backbone the rib cage protected vital organs like the heart and lungs on land without the buoyancy of water to cushion them these organs would be crushed by the Animal's weight by developing ribs ichthyostega emerged in a body that could withstand Earth's gravity and move about freely over land [Music] at long last the time had come to look beyond the water's edge a hundred million years had passed since the earliest fish ventured from the ocean into fresh water [Music] a habitat that helped shape the complex body systems necessary for life on land thank you bolstered by millions of years of evolutionary advancement ichthyostega took its first steps while an ocean of Life swam in its bones sea to River and from River to land life had taken leaps of astonishing complexity there is no way to know what called ichthyostega from the relative comfort of the river toward the challenges that awaited on land but in taking its first steps ichthyostega blazed a new Trail a path we too would forge on our own evolutionary Journey from the nurturing Seas into the great unknown

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Length: 20min 33sec (1233 seconds)

Published: Fri Nov 25 2016