from water to land
The early tetrapods were the first vertebrates to actually walk the solid earth. They began their conquest of land in the Paleozoic era around 360 million years ago. The question many paleontologists have been asking for a long period of time is whether the anatomy for locomotion on land was developed in water for swimming purposes, or if it was adapted after the creatures became terrestrial. Recent findings of fossils indicate that the transformations of the aquatic creatures happened underwater in order to help them survive in the changing world. When looking for answers, they had to examine forearm, hip, wrist, finger, and other bones, as well as the lungs or gills of the early tetrapod fossils. This information is critical in understanding the history and the process of growth and change. It aids in learning about human evolution. Tetrapods are creatures with four limbs, hips, shoulders, fingers, and toes, which developed sometime after lobe-finned fish, and before the first fully terrestrial vertebrates. The earliest tetrapod known is Acanthostega. It is also considered the most primitive tetrapod. It is very close to its fish ancestry, but still anatomically far from
its terrestrial relatives. These creatures still lived in water, but they had a lot of the terrestrial tetrapod anatomical characteristics. Zimmer, Carl. (June, 1995). Coming onto the land. Discover v16, n6 , 118 To summarize all of the findings stated above we must refer to the most logical explanation of all. Jenny Clarck proposed that fish must have evolved into tetrapods for life underwater. The lagoons were a new ecosystem in the Devonian period, but bacteria used up too much of oxygen. This was hard for the tetrapods that lived in water. Therefore they evolved lungs to help them survive. The limbs and hips aided the creatures to walk on the bottom of the wetlands. According to Zimmer the fish had to keep its fins in motion in order to remain motionless and unnoticed by the predators and the prey. The first tetrapods however, could grab rocks while waiting for prey to swim by. This shows that the tetrapods first evolved their limbs underwater, and later they started to use them on land, but for completely different reasons. 1998). Evolution of vertebrate limbs: robust morphology and flexible The next question is whether the hips developed to aid the creature in traveling distances on land or for some other reasons. According to Carl Zimmer, a walking animal's hips have to be attached to its spine in order to support it against gravity. The hips of the early tetrapods did not have the attachment of strong ligaments. Their hips were loosely attached to their spines. If the tetrapods tried to walk, they probably would have flopped around defenseless on the ground. Therefore the rear limbs were not designed for locomotion on land. The creatures' wrists were very weak, but surprisingly they had eight fully developed tetrapod fingers. These fingers were multij
Some common words found in the essay are:
Romer Harvard, Background Tetrapods, Carl Zimmer, According Zimmer, Revision Abstract, Jenny Clarck, Kathleen McAuliffe, Kathleen August, Carl June, Susan September, lived water, help survive, aquatic creatures, tetrapods lived, happened underwater help, fish developed, transformations aquatic, creatures happened, underwater help, tetrapods lived water, water land, underwater help survive, tetrapods evolved, creatures happened underwater, aquatic creatures happened,
Approximate Word count = 1200
Approximate Pages = 5 (250 words per page double spaced)
|
