Compare enough force that is required to

Compare and contrast the adaptations within amphibians and
reptiles that help with climbing.


Locomotion within reptiles and amphibians has expanded into
many forms, but one of the most commonly seen in both classes is the use of
climbing. Both reptiles and amphibians have developed substantially different
ways of overcoming this form of locomotion, comparing geckos to tree frogs
shows how they have accomplished the same goal but using drastically different
methods. Geckos adhesive abilities come from the function of their feet and the
use of hundreds of thousands of spatulae, that create the force needed to allow
them to climb (Russell, 2002). whereas frogs use large pads that are covered in
microscopic channels that lead to a mucous gland that helps them stick to
surfaces, which acts as their adhesive mechanism.

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Geckos adhesive capabilities come directly from the function
and structure of their feet (Russell 2002). On the underside of their toes are
adhesive pads, made up of hundreds of thousands of microscopic setae. Each seta
splits into hundreds of spatulae tips. When the gecko places his foot down the
said spatulae spread out maximizing their surface area. a single toe can
generate enough force that is required to hold the animal’s body weight (Autumn
and Peattie, 2002). The adhesive properties of geckos could come from van der
Waals interaction which is when atoms or molecules come so close that they are
able to form a very weak bond, However, with a lot of Van der Waals forces
interacting between two objects, the interaction can be very strong, creating
enough force to hold the gecko to the substrate. To break these bonds geckos,
use Macroscale detachment of the adhesive pads, this happens through digital hyperextension in both geckos (Autumn and
Peattie, 2002; Russell, 2002) and frogs (Hanna and Barnes, 1991). The peeling
motion of digital hyperextension may minimise the force needed to overcome the
adhesion produced by the foot. Removal of a small region of the pad at a time
by pealing is easier as only a small area is being separated from the substrate
at any given time.



Frogs possess large pads at the tip of each toe that provide
adhesion while climbing. these enlarged toe pads have evolved in multiple
different frogs. Generally, the toe is constructed of a pad with a specialized
epidermal layer, the epidermal cells are shaped into peg-like structures,
between these structures there are spaces that have channels coming from mucous
glands. These mucous glands supply the fluid that then forms part of the
adhesive mechanism. frogs toe pads allow them to adhere to surfaces through wet
adhesion. Wet adhesion is when surface tension and viscous forces keeps the
animal attached using a fluid filled joint that resists cavitation, how strong
the force is, is directly dependent on the size of the toe pad. frogs must also
be able to detach their toe pads, Frogs detach their toe pads by peeling, depending
on the direction of locomotion changes how the pads are going to be detached,
when the frog is moving in a forward direction up a vertical surface the pads are
being peeled off from the rear forwards. When walking backwards down a vertical
substrate peeling of the toe happens starting at the front of the pad and then
ending at the back. (HANNA, G., Jon, W. and
BARNES, 1991)






Other examples of reptiles that have special adaptations for
vertical locomotion would be chameleons, Chamaeleon’s are highly adapted arboreal
lizards with a laterally compressed body, zygodactylus feet and a prehensile
tail. While traveling along branches chameleons have a more upright limb
posture and walk in a more mammal-like way. Traveling between branches is not done by jumping or by the use of
sticky pads but by reaching
with their forelimbs and supporting themselves by their hindlimbs and tail
until a new perch is grasped. (Peterson, J.A.,
1984) the bones in the feet are developed differently to form limbs that
allow chameleons to hold on to narrow substrates (Peterson, 1984). arboreal
species usually have longer tails on average than that of terrestrial reptiles,
this is particularly showing in chameleons who possess long prehensile tails
that help with their locomotion and balance. Although chameleons have adapted
to be able to live within the trees they have had to compromise on their
running ability. Moreover, it was suggested that the majority of arboreal
species possessed a greater number of slow, strong, muscles fibres within its
limbs (Peterson, J.A., 1984).


In conclusion the differences between reptiles and
amphibians is substantial in the way they tackle the same obstacles, the use of
microscopic setae that form bonds that use van der Waals interactions, or the use
of specially developed limbs that allow easier gripping onto branches as well
as the use of prehensile tails that help with balance, in comparison to the use
of wet adhesion and toe pads covered in mucous glands.



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