I know in fiction Sonic The Hedgehog is able to run faster than the speed of sound but could an organism actually evolve to move faster than the speed of sound? What type of fuel would such an organism need to move faster than the speed of sound? What form of locomotion would such an organism use?
Just for the heck of it:
Yes, but only if you don't mind getting poop everywhere.
Allow me to explain.
The fastest accelerating living creature on the Earth is a fungus. This doozy of a biological marvel grows near cowpats and other faeces, and because not many animals like eating where they've just pooped, it likes to launch its spores away from where it's growing. The issue is that because the spores are tiny they have to be thrown with a lot of force, and the method by which they're thrown (essentially popping a tiny water balloon behind them) means that all the acceleration happens in the first instant of their release.
Now imagine that the animals in question develop even more of a dislike to eating where they've pooped. The fungus has to launch its spores further. To do so it can either make the spores heavier and more aerodynamic or fire them with more force. Lets assume that they evolution causes both. Heavier spores mean better chance of survival, more force means greater spread range.
Now the animals are avoiding the area for a different reason: They don't like being persistently plagued and periodically peppered by poop produced projectiles. The only solution for the plant? More power. Perhaps some ablative coating on the spores? Heck, lets assume evolution gets lucky and evolves a two-stage projectile (because one explosive launch isn't enough).
Eventually you'll reach a point where the fungal spores (briefly) break the sound barrier on their trip out from their parent body. You'll also reach the point where the recoil from such supersonic sporulation sprays a substantial slurry subsisting of water, poop and fungal fruits all over, giving the animals that pooped in the first place even less reason to go anywhere near their increasingly hostile toilet environment.
Dung cannon fungus indeed.
Only if evolution demanded it
Let's lay down some numbers to start with.
- Speed of sound in air: 343m/s 1225km/h
- Speed of sound in seawater: 1500m/s 5400km/h
The fastest moving animal in air is the Peregrine Falcon 389km/h, just over 30% of the way there accelerating by gravity with a highly streamlined form. By contrast a normal human falling in air will hit around 200km/h. Felix Baumgartner is the exception to this having actually broken the speed of sound in freefall.
So we know it's possible now all you need to do is give your animal both the reason and the ability to fly at those altitudes.
Highest flying bird: Rüppell's vulture at 11,300 meters. Baumgartner in contrast flew to 38,969.4 meters, so we're just over 25% of the way there. Except we're not, we're closer. Baumgartner went supersonic at 33,446m but didn't drop back to subsonic until 22,907m and given that the peregrine can dive at nearly twice the speed of a human in normal circumstances and from only 1000m we're a lot closer than it initially looks.
The only reason birds can't dive at supersonic speeds is that they don't fly high enough. The fact that they probably wouldn't survive the attempt is a secondary detail. Hunting doesn't require it, escape from hunters doesn't require it.
Why did I mention seawater? The fastest fish is the Black Marlin at a mere 129km/h, that doesn't even come close. It's because of the mantis shrimp which, while it punches at a mere 23m/s, needs to hit 102,000 m/s2 acceleration to get there. Now there's an animal with potential.
If your animal competes for mates by racing then the maximum speed is only limited by physics. Assuming that these critters were already fliers than a mating season flying contest at consisted of climbing as high as possible and diving straight down could eventually result in a supersonic buzzard. In evolution sex is a powerful force.
As @Separatrix has kindly mentioned, there are natural ways to break the sound barrier (namely freefall or ejection), but for a creature to sustain supersonic flight for any length of time it will need some sort of thrust. Unfortunately, there are problems with most of the common forms of thrust.
Problems with Jets
Modern supersonic aircraft produce this thrust via rocket or jet engine. There are jets that require few moving parts (ramjets, for example) but these usually cannot be ignited until the craft is already travelling at an incredible speed. Otherwise the creature would have to evolve some sort of turbine, which seems unlikely.
Problems with Propellers
Prior to jet engines most aircraft were prop-driven. Even today the propeller is in common use. Has a prop-driven aircraft ever broken the sound barrier? Unfortunately no. Our friends over at Aviation have answered a related question here which discusses the issue in detail, but in summary the propellers themselves would end up breaking the sound barrier before the entire aircraft could, and the airflow/structural problems associated with this are seemingly insurmountable. Also, I am not aware of any life form evolving any sort of spinning component comparable to a propeller, or even a wheel for that matter, so propellers seem unlikely.
Problems with Wings
Most living things fly on wing power, essentially swimming through the air. The variety in wing design is extensive, but to my knowledge no creature has wings that flap even close to supersonic speeds. If a bird or bug were to try to break the sound barrier, their wings would have to be travelling even faster than this during the forward stroke. This is part of the reason helicopters do not travel supersonic: the forward-rotating side of the rotor blades would break the sound barrier before the entire craft would, and cause major aerodynamic and structural problems.
The stress on an aircraft as it breaks the sound barrier is immense, and the violence of the pressure wave involved is game-breaking but optimistically I suppose it could be possible for a creature to evolve some sort of rigid bone structure and tough outer shell that could withstand these conditions. I believe @Cort Ammon linked a related worldbuilding question about dragons going supersonic. The best solution I can think of would be a creature that somehow store a volatile fuel, somehow has a ramjet, and somehow manages to climb to a suitable altitude that it can freefall to a speed at which the ramjet can be ignited. Rocket propulsion is also a solution, since the creature could avoid the need for freefall, but internal oxidizer would also need to be stored, so it would be a tradeoff.
Alright guys, let's deal with it:
it's impossible for an animal to break it on it's own, so let's first get a normal bird. It can't go really fast. Honestly, I don't even think that they can reach 60 km/h on their own without wind, but probably they wouldn't be capable to reach this even with wind.
- feathering - Bird's most important thing
- light bones - the only reason they can fly... I mean... just glue feathers on your arms and try to fly
- They are aerodynamic- the only way to go in the air.
So, Let's try to make the best flying creature.
- Bones - Light, same as the bird ones
- Organs - similar to the bird ones, but of course with bigger lungs so it's organs can't overheat
- Weight - let's say about ton...
- Height - around one meter and half
- Length - about 17m from the tail to the top if its head
- Wings - around 5m ↔ 7,5m ↕
- Musculature - its musculature must be hundred times stronger that the strongest bird we know
It still won't be capable to break the sound barrier
ALL evolution proceeds via the removal from the gene pool those members which are not so much "barely fit" (since some of them do reproduce), but those variations which are actually unfit to meet the changing challenges imposed regardless what those challenges are specifically. In order to decide if any conjectured evolutionary path is plausible (in this case the evolution of something that could propel itself at greater than Mach 1), would require many iterations of elimination of the slowest members of each population (more specifically it would require some factor that would act to that effect that did not place excessive demand on the rate of change). It also has to be not only physically possible, but it needs to adhere to the significant restrictions inherent with "descent with modification" which is to basically rule out radical changes from one generation to the next. Given the later factor I'd say that the speed challenge would have more possibility of producing a result if it applied to a wide range of species rather than just one.