<span>The structure of the feet and legs varies greatly among frog species, depending in part on whether they live primarily on the ground, in water, in trees or in burrows. Frogs must be able to move quickly through their environment to catch prey and escape predators, and numerous adaptations help them to do so. Most frogs are either proficient at jumping or are descended from ancestors that were, with much of the musculoskeletal morphology modified for this purpose. The tibia, fibula, and tarsals have been fused into a single, strong bone, as have the radius and ulna in the fore limbs (which must absorb the impact on landing). The metatarsals have become elongated to add to the leg length and allow the frog to push against the ground for a longer period on take-off. The illium has elongated and formed a mobile joint with the sacrum which, in specialist jumpers such as ranids and hylids, functions as an additional limb joint to further power the leaps. The tail vertebrae have fused into a urostyle which is retracted inside the pelvis. This enables the force to be transferred from the legs to the body during a leap </span>
<span>The muscular system has been similarly modified. The hind limbs of ancestral frogs presumably contained pairs of muscles which would act in opposition (one muscle to flex the knee, a different muscle to extend it), as is seen in most other limbed animals. However, in modern frogs, almost all muscles have been modified to contribute to the action of jumping, with only a few small muscles remaining to bring the limb back to the starting position and maintain posture. The muscles have also been greatly enlarged, with the main leg muscles accounting for over 17% of the total mass of the frog.</span>
Answer:
I believe you just answered it yourself. they development an immunity to insecticides the more they are exposed to it.
Answer:
This question lacks options, options are:
a) indirect
b) mosaic
c) determinative
d) regulative
e) direct.
The correct answer is d.
Explanation:
The egg (ovum) like the embryo during the first embryonic divisions, do not possess any sign of polarity. This development mechanism can be called regulative development(in contrast to the mosaic model) since the fate of the cells that originate is not fixed and can be modified during development. In regulative embryos, part of the embryo can be removed and the remaining cells can compensate for the loss and give a complete individual as the final product.The strongest evidence that continues to support this regulatory model is based on the plasticity or potential that mammalian cells possess before implantation. It is known that the blastomeres produced by the first divisions can be replaced with each other or even can be eliminated without apparently altering the embryonic development and therefore they are equivalent (without polarity).
Phosphorus. It's not abundant, but it's important. There are traces of it in our bones and in the "phospho-lipid bilayer" of the membrane.
Hope that helps!
