Question

Address the following topic in 100-150 words. Snakes began evolving 100 million years ago as terrestrial, 4-limbed lizards. Hind- and forelimb structures disappeared over millions of years, except for a few python and boa species today that still have vestiges of internal skeletal limb structures but no legs. How would an evolutionary biologist explain how lizards evolved into limbless snakes?

Answer 1

Snakes were actually originated at least 100 million years ago. few experts contend that snakes evolved on land and lost their limbs first the forelimbs, then the hindlimbs as they adapted to a burrowing lifestyle. Others prefer the hypothesis that they evolved from a group of aquatic reptiles, and lost their limbs as they adapted to the sea. Either way, snakes probably descended from a lineage of fully legged lizards based on three general lines of evidence. First, snakes are genetically nested deep within the lizard clade . Second, the fossil record of snakes includes several species that retained hindlimbs , Eupodophis, Pachyrhachis, with a recently discovered putative snake that possessed all four limbs Tetrapodophis. Finally, some of the earlier branches of the snake phylogenetic tree, particularly boas and pythons, include species that possess embryonic hind limb buds that fail to develop into fully formed limbs. natural selection prevents animals from losing the genes that are involved in developing appendages, how is it that species like snakes have lost their limbs One probable pathway is via the disruption of DNA regions known as enhancers. Enhancers are not genes, meaning they do not encode a protein, but they do regulate gene activity. They do this via proteins known as transcription factors, which bind to the enhancers, leading to the transcription of a nearby gene. Multiple enhancers can be associated with a single gene, and different transcription factors bind to distinct enhancers, controlling when and where the gene is turned on. The regulatory effects of transcription factors and enhancers helps to explain how an entire organism can develop from a single, undifferentiated fertilized egg. As sets of regulatory proteins interact with distinct enhancers, they direct different sets of genes to express themselves in various locations. This allows cells to specialize and differentiate, eventually forming tissues and organs.An important challenge in evolutionary biology is to understand how major changes in body form arise. The dramatic transition from a lizard‐like to snake‐like body form in squamate reptiles offers an exciting system for such research because this change is replicated dozens of times. Here, we use morphometric data for 258 species and a time‐calibrated phylogeny to explore rates and patterns of body‐form evolution across squamates. We also demonstrate how time‐calibrated phylogenies may be used to make inferences about the time frame over which major morphological transitions occur. Using the morphometric data, we find that the transition from lizard‐like to snake‐like body form involves concerted evolution of limb reduction, digit loss, and body elongation. These correlations are similar across squamate clades,A major goal of evolutionary biology is to explain the remarkable diversity in morphology among multicellular organisms, and especially the dramatic transitions in body form or body plan that sometimes occur between and within clades