[Music] [Music] mollusks like this garden snail it's just one of over 150,000 different mollusks that flourish today but when they first appeared over half a billion years ago mollusks were but tiny creatures inching around under a protective [Music] shell how did the struggle for survival create so many variations on their original body plan they face a world of attackers hungry for their protein Rich sweet tasting [Music] flesh but mollusks have survived because their body parts manag to change as new challenges [Music] arise the basic toolkit of a mollusk is evident in the abalone most mollusks have some kind of foot for many including the abalone the foot muscle bestows Mobility when the foot brings them to food mollusks eat by using a unique rasping tongue called a radula covering the vital organs is a fold of skin called the mantle it's the mantle that secretes the trade Mark body armor of so many mollusks the [Music] shell the leafy horn mouth has developed just three well-placed ridges along its shell [Music] these ridges add just enough thickness to foil a crab's attempt to get a shell breaking grip but since no shell provides perfect safety some mollusks have added another method of [Music] Defense they've developed the means to outrun their enemies an abalone spends most of its life clamped to rocks but when Escape is necessary its muscular foot sets out across the bottom the foot is a biomechanical Wonder with no bones for support it can stretch out to crawl while holding on at the same time the Abalone employs its foot when a dangerous adversary is close by such as the many armed predatory sea Star pnip podia the Abalone could clamp itself down but then it would face the slow suffocating torture of pnip podia death [Music] grip so the abalon using just one foot attempts to outrun pnap podia which has more than 10,000 tube feet all moving with lock step [Music] [Music] deliberation because the abalone's foot is attached to its shell it can twist with powerful torque and wrench itself free when its pursuer catches up but competition has driven other mollusks to turn this defensive tool into a weapon that kills where cockal are abundant they attract the attention of a more aggressive mollusk the moon snail can inflate it foot to four times the size of its entire shell a foot that serves as both a burrowing tool and a predatory weapon the cockle however has a few tricks of its own its foot is a powerful Digger but it can also kick away forcefully when danger approaches [Music] if the moon snail loses its hold it can also burrow down and surprise a buried [Music] cockle this time the aggressor succeeds [Music] the moon snail's enormous foot begins to smother the hapless cockle even a hard shell can't stop the well equ equipped moon snail which can drill right through to feed on the animal Within [Music] the need to procure a meal is a driving force in Nature's arms race and mollusks have evolved an astonishing variety of feeding tools for the job peering inside in abalone's mouth we can see one of Nature's brilliant and bizarre Creations it's called a radula a rasping ribbon teeth like a chainsaw blade in some mollusks these teeth contain a hard iron mineral that grants them Supreme durability this electron micrograph of the abalon radula shows why it's so Adept at tearing through kelp other mollusks have evolved rajulas suited for different tastes this one opens Barnacle shells this one can scrape through animal flesh the compulsion to eat and to avoid being eaten has inspired endless invention The War Began among bottom dwellers confined to the sea floor [Music] an Innovative mollusk evolved the ability to swim by floating off the bottom it was a miraculous step in the survival game examining the Nautilus we can see how Evolution transformed a mere bottom feeder into a buoyant battleship [Music] at its head a mass of 90 or more muscular tentacles can extend from sheaths to seize its prey nautiloids found a way to swim by jet propulsion water is taken in and rapidly forced out of a funnel that steers and propels the Nautilus it evolved from the ancient foot to become like like a flexible exhaust pipe that also serves as a Rudder every feature of the Nautilus design is a legacy from its ancestors and the world they encountered but what set this line of mollusks apart from all that came before was a key evolutionary breakthrough buoyancy but soon the battle for survival would change dramatically thanks to a new weapon [Music] speed fish had been around for millions of years but now they began to evolve quicker more agile bodies which greatly enhanced their hunting skills in time the floating fortresses were outgunned but mollusks fought back once again mollusks retooled one line embarked on a risky scheme it would gain speed by forfeiting more and more of its heavy protective shell in squid living today only a thin remnant of shell remains on the the animals inside now it provides support for a streamlined body that's become a kind of natural rocket some squid are capable of accelerated bursts traveling as fast as 20 mph compared to the mollusks that came before squid are superb swimmers they improved on the jet propulsion system of nautiloids sucking water into their body then expelling it forcefully and over time they evolved a mantle wall that was muscular and strong elastic fibers in the muscle intensify The Recoil that expels the jet of water triggering this action at lightning speed is a nerve system WI ired with giant nerve fibers and every squid is powered by three hearts which can pump blood and deliver oxygen as fast as in humans but beyond their speed and evasive maneuvers squid went even farther venturing into the deep sea these squid must survive the extraordinary rigors of the deep deep and like so many mollusks they have adapted in singularly creative [Music] ways but another mollusk has gone even further developing the most impressive weapon of all intelligence descended from swimming ancestors octopuses returned to live on the bottom a tremendously risky move for an animal without a protective shell to survive there the octopus made dramatic changes to the mollusk body plan one way is the miracle of camouflage the octopus can change color and texture in an instant for the mollusk without a shell nature invented the ultimate [Music] skin the poisonous blue ring octopus flashes its colors as a [Music] warning yet another brilliant design for the arms race [Music] its early ancestors were at the mercy of shell Breakers now the crab must reckon with the octopus an adversary equipped with intelligence an awesome ability for disguise and a devastating eight armed attack [Music] do mollusks possess some secret weapon in the battle for survival the simple truth is they endure because their body plan adapts endlessly and ingeniously [Music] across millions of years they have shown that the ability to change in an Ever Changing world is perhaps The Greatest Secret of the survival game e