With fossils similar to whales being found it is becoming difficult to distinguish the four legged land mammals from the aquatic whales, making evolution a considerable explanation.
Their flippers are used to stabilize the dolphin as they swim. Whales have similar features with the hippopotamus like the distinct structure of the ancient walking whales ankles, which are found in hippos and in their close relatives. The skulls of these extinct creatures show that their nasil opening was not located at the top of the head like whales of today and were not located in the front like land mammals, instead it was located in the middle.
But the movements of the femur are extremely limited, and in two of these whales the hip-joint as firmly anchylosed, in one of them on one side, in the other on both sides, without trace of disease, showing… [END OF PREVIEW].
They "speak" through a "melon organ" or pad of fat. Recent fossil discoveries in Pakistan have solved this mystery and it is possible to see the stages in the transition of these cetaceans from land to sea.
The earliest archaeocetes had limbs and pelvis attached to the vertebrae by a sacral joint, but later on the limbs and pelvis became detached from the rest of the skeleton, though the bones still remain. 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.
Professor Hans Thewissen explained the differences of earbone fossils, the incus and tympanic, in his web publication, The Thewissen Lab Thewissen, Their teeth, like most land mammals, show several types molars and bicuspids, etc.
These have been studied in greatest detail, but because the sperm whale has the largest brain on earth, has great commercial significance, and has a highly social lifestyle, it has received the most attention.
These include the baleen whale families Balaenopteridae including the blue whale and Balaenidae right whalesand the toothed whale families Delphinidae dolphins and killer whalesPhyseteridae sperm whalesMonodontidae belugas and narwhalsPhocaenidae porpoisesand Ziphiidae beaked whales.
By the Miocene period, whales of both lineages were relatively common and are found as fossils in many marine deposits. The modern-day whale still has the remnants of hind legs in their bones, in the form of an extra, floating bone, the remnant of the thigh bone, in the area of the lower stomach.
These whistles are used to communicate alarm, sexual excitement, and perhaps other emotions.
Gradually their legs grew smaller, as they spent more time in the water, and began to look like sea otters, with abilities to dive for long periods of time, developed longer front legs than hind legs, which shrank, for they still went onto land at times.
Instead of a major blood supply to the brain on the outside of the neck, the dolphins blood flows through an artery in the vertebrae that provides a constant supply of blood, which is most essential when diving into the depths of the ocean.
Fossil records of two species of extinct basilosaurid whales that lived about 34 — 40 million years ago act as a third source of evidence. The DNA of whales has been compared to many other animals like, fish and sea lions but has only been closely matched to the DNA of a hippo. Thewissen which are available on the Web Thewissen.
The skulls of these extinct creatures show that their nasil opening was not located at the top of the head like whales of today and were not located in the front like land mammals, instead it was located in the middle.
The function point-of-view fails to account for the presence of a femur in addition to processes from the pelvic bone.Braided Essay: Blood dolphins and Endangered Species As my cruise ship approached the port we were about to dock at, I stood near the railing looking down into the beautiful water.
Even from fifty feet up, I could see straight to the bottom of the crystal clear water. Penguin Evolution Essay - On our Earth, we are graced with many fantastic life forms. From those gliding through the heavenly skies, to those at the deepest depths of the oceans, there is a plethora of various species.
Evidence of Evolution Essay Sample. Embryology, the study of how creatures develop before being born or hatching, is more evidence of evolution. Dolphins and human embryos look similar at around the same stage of development, they both appear to have arm and leg buds.
Humans later develop legs but in dolphins they grow for a while. Dolphins normal heart rate is BMP, but evolution stepped in and created the retia mirabila which is a dense mass of blood vessels found under the ribcage that acts as a sponge allowing the dolphin to dive to deep depths without passing out.
This essay will explain some features of how dolphins evolved physiologically to become better suited to their environment. How the Dolphin has adapted to its current environment The most common misconception is that dolphins are fish, but they aren’t, they are actually mammal’s called cetaceans.
Evolution involves changes in the genes that are present in a population.” In other words, author says that the same animal is transformed the higher level.
whales and dolphins Essay Mostly whales and.Download