How would a biologist explain the presence of palm lines and their relevance?
All answer given so far are totally right!Let us summarize it:"The lines on a palm, or palmar flexion creases, help the hand's skin stretch and squeeze."by Ariel LedermanBut there is another important point: Grip.Did you ever ask yourself, why you get these wizenly hands and feet after bathing? Well it is actually for your better grip so that you don't slip too easily.We don't know it for certain, but we think that shrivel the skin is a result of evolution. It facilitated the ancestors of man, to collect food in the water and on a wet floor as well granted a better grip on wet stones like in caves. Perhaps the effect was already there in primates, which move on hands and feet. This may explain why both, fingers and toes are wrinkled in the water.Update:Even outside the water and not wizened the structure gives us a better grip e.g. for climbing a tree (advances for fleeing from predators or collection food). There are animals which perfected this strategy, they can with their specialized toe pads climb over smooth and vertical surfaces as glass, and even cross indoor ceilings with ease.Gecko foot on a vertical glassExcursus Geckos:They use fine adhesive hairs on the soles. There are some of the finest hairs that are found in nature which are about 500 times thinner than a human hair. No surface is smooth so they stick because an electrical attraction between the molecules of the wall and the hairs (van der Waals forces).So this is probably also the trick Spiderman uses to climb skyscrapers (...).
How can ants climb walls vertically? Doesn't gravity act against them?
Gravity excludes none. It certainly act on all that creatures climbing on the walls!Well, lots of insects have little pads, called arolia, between the hooked claws on the tips of their legs. They can stick to smooth surfaces with these pads using the same principle as those pieces of plastic, which use the same basic principle as a suction cup--a vacuum.When climbing on rough surfaces, such as a wall or ceiling, a vacuum can't be formed, so they use those tiny little claws. If you could see the surface of your walls and ceilings through a microscope, you'd see there are plenty of places for tiny things to put their hooks and climb away.Ants can generate more than enough force to keep their tiny, air-filled bodies from falling, generally speaking. Sometimes they do fall, though; you just need to watch them often enough, and on the right kind of surface. Most insects have two sets of climbing tools on their feet, one for smooth surfaces and one for rough surfaces.Some insects have the additional capacity of being able to secrete a thin film of oil on the pads, which gives them even greater sticking power, mostly because it gives an even better vacuum, and also has surface tension effects. Just try taking a square millimeter of thin plastic with a micro-drop of corn oil on it, and see if it won't stick to your ceiling or any other surface.For us, wall looks smooth, but for tiny creatures, there are lot of steps.Structure of ant leg:Source: How can ants walk on walls and ceilings?
How can a lizard run on ceiling without falling down?
Only certain lizards can climb and cling to surfaces, notably geckos (which is an entire infraorder of lizard). They are able to do so because of tiny hairs on their feet call setae.
Is it possible to climb on walls?
Don’t ask ‘if’?, learn to ask ‘how?’.Basic answer is yes.The basic techniques depend on the surface material properties (surface roughness) and the geometry.Geometry: you have another answer which shows chimneying. A basic climbing technique.Surface roughness: suction is shown in media with suction cups. In climbing, we can drill holes into rock and place expansion or contraction bolts, or in rock exploit crack weaknesses for pins or hooks, etc. The first of the most experienced climbers, Messner, in his first English translated book has a short chapter on how he chanced on a town square where they had a greased pole climbing contest. He won. Find his book to learn how.
What maximum weight would an animal have to have to be assured of surviving a fall from 5000 metres onto a horizontal concrete surface?
Terminal velocityAnts can fall from this far because their terminal velocity is very low. That’s because they have a high projected area to mass ratio. A is large compared to m.But large animals have small A’s compared to their m’s. That’s thanks to the square-cube law:Square-cube lawIn English, this means that your mass increases with the cube of your radius, but your surface area only increases with the square. So double your radius, and you quadruple your area…but you octuple (multiply by 8) your mass.Get big enough (say elephant sized) and you plummet to Earth at hundreds and hundreds of meters per second.And since kinetic energy is related to velocity:[math]ke = \frac{1}{2}mv^2[/math]the faster you go, the harder you thump.So what maximum mass could an animal have in order to not die when dropped from this height? It’s hard to say - animal projection areas vary. But frogs regularly survive this - they are picked up by tornadoes from time to time and dropped (safely) back to Earth from high altitudes. Birds also survive falls when they hit high windows.But cats don’t survive very long falls.So my guess is that the maximum mass is somewhere in the 1kg neck of the woods. My dogs are about 5 kg, and I have little doubt that a 5km drop would kill them instantly. Large birds would fare better - their wings increase their projection area. So maybe a 2kg duck might survive a free fall. But for an average animal, I’d think you’d have to come down to 1kg or less to guarantee survival.
Why do lizards not fall from the wall?
There is so simple reason behind this.Have you ever seen the leg of lizard from below.If not then try to (if you have no fear of them)look of a baby lizard (it is very difficult to catch a big one).You will notice that they have a pad like structure on each finger . Those are the secret behind there special power.Actually those pads have very very very very small hair like structures.So when a lizard walk,run or remain sill on the walls those hairs get inside the irregularities of wall(that are extremely small)and produce friction due to which the lizard remain on wall .