What are the explanations for the emergence of bipedalism? how can it be identified in the fossil record?

Explanation:

The evolution of bipedalism (walking upright) signals the origin of hominid evolution, although no one is positively sure why bipedalism developed. The reason why bipedalism evolved in hominids remains a matter of discussion. No tools emerged until 2.5 million years ago, so toolmaking seems an improbable cause. Alternative ideas suggest that walking upright is more agile and uses less energy than walking on four legs; an upright posture allows hominids to pick fruit from trees and see over tall grass; upright reduces the body surface exposed to the sun’s rays; an upright stance aided the wading of aquatic hominids, and that bipedalism frees the forelimbs of males to carry food back to females, encouraging pair-bonding. All of these suggestions have their proponents, and none are universally accepted.

Fossils demonstrate that bipedalism extended back 4 million years ago; knee joints, pelvis, and leg bones all exhibit the signs of an upright stance. Remarkable evidence that early hominids were bipedal is a set of some 69 hominid footprints found at Laetoli, East Africa. Their footprints preserved in 3.7-million-year-old volcanic ash.  

prokaryotic cells do not have a nucleus in which the dna is stored in, it floats freely inside the cell.

eukaryote cells do have a nucleus in which the dna is stored in.

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.