The difference between porpoises and dolphins has led to considerable confusion, as it can be called by both names. There is, however, a technical difference: This is now widely accepted, though it has received little attention in the controversies that may concern the evolution of whales except from a few cetologists. Science is day by day adding to our knowledge about animal social systems and behavior.
Download this Term Paper in word format. The function point-of-view fails to account for the presence of a femur in addition to processes from the pelvic bone. Altogether, these hind legs in this whale present for contemplation a most interesting instance of those significant parts in an animal -- rudimentary structures.
Today it is just a double or single blowhole, and the ears are closed and internal, detecting only vibrations from the lower jaw. They "speak" through a "melon organ" or pad of fat. Milinkovitch used results from molecular studies to determine that sperm whales were more closely related to the baleen whales mysticeti than to toothed whales Odontoceti Milinkovitch.
But his conclusion was not well accepted, as sperm whales have substantial teeth and a single, rather than double nostrilled blowhole.
More recently, scientists came back to the traditional arrangement, that the sperm whale is an odontocete. The evidence and recent molecular analyses strongly indicate the mystecetes and all other extant cetaceans is the oldest division in the ancestral tree.
The pygmy sperm whale Kogia beviceps and dwarf sperm whale Kogia simusare much smaller. The kogiids seem to have separated from the lineage that led to the sperm whale at least 9 millions years ago, making the sperm whale the myse phylogenetically distinct of all the seventy-five-odd species of living odontocetes.
There are photographs of hind limb buds on a five-week-old Pantropical Spotted Dolphin embryo, and 1. Thewissen which are available on the Web Thewissen.
Sirenians and elephants are evolved from a common ancestor. Like whales, sirenians returned to the water. Though hind limbs on whales may be hard to find, many sirenians Manatees still retain vestigial toenails like their elephant cousins, and share other traits in common with modern elephants.
There seems to be a controversy over the origins of modern whales which retain vestigial hind limb rudiments. Creationists call this vestige bone disease and say these remnants were designed for copulation only which they are used forbut science says this is how evolution works --finding new purpose for old structures.
On questions on the dating of varied early whales one might suggest further reading on whale evolution, the evolution of eco-location, the nursing of the young suggesting common ancestry with land mammalsand the brain of humans vs.
The transitional inner ear of whales evolved from land to sea mammals.
Professor Hans Thewissen explained the differences of earbone fossils, the incus and tympanic, in his web publication, The Thewissen Lab Thewissen, Even better, ina historical record and photos of a female humpback with protruded hind limbs including femur, tibia and tarsus was made.
Inthere was a study of protruded limbs on whale and dolphin embryos. A female sperm whale was caught in Upon examining the interior of the limb, partially cartilaginous bones were found, corresponding to the pelvis, femur, and possibly to the tibia.
As there are numerous examples of this feature, a list of catches between and of whales caught and discovery of hind limb protrusions, including the approximate percentage of whales with this feature may be found on the web.
These include the appearance of the first elephants with trunks, early horses, and the appearance of many grass plants that would eventually produce vast tracts of grasslands in Mongolia and North America for these animals to eat in the following epoch, the Miocene.
Two modern lineages of cetaceans had evolved during this epoch from archaeocete ancestors. Interestingly, in the late Oligocene, the whale Aetiocetus, from Oregon, developed skull and jaw features typical of baleen whales, so it is considered to be the earliest mysticete.
Yet it also had a full set of teeth.
By the Miocene period, whales of both lineages were relatively common and are found as fossils in many marine deposits. As a result of the cooling trend prevalent throughout the Oligocene period, the lives and habitats of many organisms were directly affected.
In the oceans, marine biotic provinces became more fragmented as sea dwellers capable of withstanding cooler temperatures congregated to places further from the warmer equator, where other species could better survive.View this term paper on Evolution of Whales and Dolphins.
The dolphins breathe through their nose but whales' nostrils drifted back farther and farther onto Term Paper Evolution of Whales and Dolphins and 90,+ more term papers written by professionals and your peers.
The humpback whale is a large yet beautiful creature of the deep. It’s kingdom is Animalia, Phylum: Chordata, class: mammalia, Order; Cetacea, Family; Balaenopteridae, Genus; Megaptera, Species; Novaeangliae.
|Evolution Of Whales And Dolphins Term Paper - Words||Whale reproduction Breeding behavior is complex and often involves three or more animals.|
|Part 2 Outline||The Environment The humpback whale is a large yet beautiful creature of the deep.|
|Essay, term paper, research paper: Science Reports||A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation for example, the large muscles of a weightlifter. Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment.|
The evolution of the whales is controversial due to it being hard to find a fossil. In their evolution, dolphins and whales began with an animal with a long nose and sleek body, with short legs, like weasels About 60 million years ago, as whales first entered the water, they looked kind of like a crocodile, with their long noses and short legs.
Evolution is change in the heritable characteristics of biological populations over successive generations.
These characteristics are the expressions of genes that are passed on from parent to offspring during timberdesignmag.coment characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation.
Essays in Natural History and Evolution: THE ESSAY in science is an art form as well as a means of communicating ideas.
All scientists publish their findings somewhere, but . The Evolution of Whales The origin of modern day whales, a mystery that has puzzled paleontologists for years, may have just been solved with the discovery of an ankle bone.
This discovery might sound simple and unimportant, but the bones of these ancient animals hold many unanswered questions and provide solid proof of origin and behavior.