Analysis of their degrees of similarity reveals clear time-progressive evolutionary patterns within the suborders. By the end of the Permian three of the six were extinct and by the end of the Triassic five were; they failed to evolve further and failed to live on unchanged.
Science Reports term papers Disclaimer: Free essays on Science Reports posted on this site were donated by anonymous users and are provided for informational use only.
The free Science Reports research paper Transitions of Reptiles to Mammals essay presented on this page should not be viewed as a sample of our on-line writing service. Transitions of Reptiles to Mammals A long long time ago, in a galaxy not too far away, was a little blue planet called Earth, and on this world not a single mammal lived.
However a lot of time has past since then and we now have lots of furry creatures that are collectively called mammals. How did they get their? Where did they come from? These are the kinds of questions that led me to my subject of choice.
I will endeavor to provide examples, using specific transitional fossils, to show that mammals have evolved from a group of reptiles and were simply not placed here by unknown forces. Before I begin, I would like to define some terms so that nobody gets left in the dust. The term transitional fossil can be used in conjunction with the term general lineage, together they help explain the how one species became another.
This is a sequence of similar genera or families, linking an older to a very different younger group.
Each step in the sequence consists of some fossils that represent certain genus or family, and the whole sequence often covers a span of tens of millions of years.
A lineage like this shows obvious intermediates for every major structural change, and the fossils occur roughly but often not exactly in the expected order.
However, usually there are still gaps between each of the groups. Sometimes the individual specimens are not thought to be directly ancestral to the next-youngest fossils e.
However they are assumed to be closely related to the actual ancestor, since the have similar intermediate characteristics. Where Does It All Begin?
Mammals were derived during the Triassic Period from to million years ago It began with relatively warm and wet conditions, but as it progressed conditions became increasingly hot and dry. The therapsids, members of the subclass Synapsida sometimes called the mammal-like reptiles ,generally were unimpressive in relation to other reptiles of their time.
Synapsids were present in the Carboniferous Period about to million years ago and are one of the earliest known reptilian groups.
Although therapsids were primarily predators by nature, some adaptations included a herbivorous species as well, they were generally small active carnivores. Primitive therapsids are present as fossils in certain Middle Permian deposits; later forms are known from every continent except Australia but are most common in the Late Permian and Early Triassic of South Africa.
The several features that separate modern reptiles from modern mammals doubtlessly evolved at different rates. Many attributes of mammals are correlated with their highly active lifestyle; for example, efficient double circulation of blood with a completely four-chambered heart, anucleate and biconcave erythrocytes blood cellsthe diaphragm, and the secondary palate which separates passages of food and air and allows breathing during mastication chewing or suckling.
Hair for insulation correlates with endothermy being warm-bloodedthe physiological maintenance of individual temperature independent of the environmental temperature, and endothermy allows high levels of sustained activity. Transitions to New Higher Taxa Transitions often result in a new "higher taxon" a new genus, family, order, etc.
There is nothing magical about this.Transition from synapsid reptiles to mammals. This is the best-documented transition between vertebrate classes. So far this series is known only as a series of genera or families; the transitions from species to species are .
Transitions Of Reptiles To Mammals Essay Words | 12 Pages. Transitions of Reptiles to Mammals A long long time ago, in a galaxy not too far away, was a little blue planet called Earth, and on this world not a single mammal lived. Transition from amphibians to amniotes (first reptiles) and apparently produced the mammals.
Some transitions among reptiles. I will review just a couple of the reptile phylogenies, since there are so many. Early reptiles to turtles: (Also see Gaffney & Meylan, in Benton ). The several features that separate modern reptiles from modern mammals doubtless evolved at different rates.
Such a pattern of evolution is termed mosaic and is a common phenomenon in those transitions marking the origin of major new adaptive types.
Transitions of Reptiles to Mammals A long long time ago, in a galaxy not too far away, was a little blue planet called Earth, and on this world not a single mammal lived. However a lot of time has past since then and we now have lots of furry creatures that are collectively called mammals. This is a tentative partial list of transitional fossils (fossil remains of groups that exhibits both "primitive" and derived traits).
The fossils are listed in series, showing the transition from one group to another, representing significant steps in the evolution of major features in various lineages.