Whale Evolution
Ailyng1118Whale Evolution
"Blue whales are the largest animals ever known to have lived on Earth. These magnificent marine mammals rule the oceans at up to 100 feet (30 meters) long and upwards of 200 tons (181 metric tons). Their tongues alone can weigh as much as an elephant. Their hearts, as much as an automobile.
Blue whales look true blue underwater, but on the surface their coloring is more a mottled blue-gray. Their underbellies take on a yellowish hue from the millions of microorganisms that take up residence in their skin. The blue whale has a broad, flat head and a long, tapered body that ends in wide, triangular flukes." -National Geographic
Ailyn Guanajuato & Isabel Hammer
Pakicetus
One of the first whales were the Pakicetus. Pakicetus were land animals, with a long skull & large carnivorous teeth.
Another early ancestor of the whales is Indohyus.
Ambulocetus
With it's hands & feet enlarged like paddles, legs are shorter and tail longer
Early Aquatic Whale
Ambulocetus fossils prove that the whale lived the aquatic life, from the isotopes of oxygen in it's bones. The isotope show from the whale it was most likely that they drank salt & fresh water.
Whales evolving after Ambulocetus such as Kutchicetus, Rodhocetuss, Dorudon, and many more. All show higher levels of saltwater oxygen isotopes
With the whales evolving so much into the aquatic life, they evolved blow-holes (nostrils) further back on their skulls
Ambulocetus Natans in action.
More aquatic whales showed other changes relating to whales today. For example the Pelvis; reducing in size and separating from the backbone. With the whales evolving from land animals to aquatic, they're backbones didn't naturally bend side to side instead going up and down.
Similar to mammals such as seals and dogs. With dog's spines moving the same way as whales.
More ancestors
Dorudon & Basilosaurus
With them beginning to swim, other changes started happening to their skeletons. In which their limbs were used for steering not padding.
"The sequence of the whales' tail vertebrae matches those of living dolphins and whales, it suggests that early whales, like Dorudon & Basilosaurus, did have tailfins."-Philip Gingerich
40 millions years ago these ancient whales evolved.
Dorudon (left)
Basilosaurus (top)
Skeletons of whale ancestors (bottom)
Hind-limbs of these whales were about non-existent. Scientists believe that the hindlimbs have been internal to the body wall.
Timeline
The Hippo
The Hippo, relative of Whales.
Some of a Hippo's adaptations are that they either live in as solitary animals or in groups of a hundred or more called "schools". In these schools there is one overly territorial bull that is dominant, which is the only male with the ability to reproduce.
Hippo's spends majority of it's time in water to keep self cool. It has the ability to walk on the bottom of lakes, rivers & streams due to its weight. During the day it spends its time sleeping mainly near water or in, and night time it comes out and grazing.
Hippos can stay underwater for 3-5 minutes, they can submerge themselves underwater by closing eyes, nose and ears.
Modern whale adaptations
Local or regional
The mammals that roamed the land & diversified greatly after Dinosaurs were Condylarths. They are considered a common ancestor of modern day whales. Mesonychidaes (Middle Claws) then developed from Condylarths, they are large bodied animals. They live in or near rivers & lagoons. They lived during the Paleocene period, they adapted for the capture of fast-swimming fish.
When they went into the seas, they became the oldest now extinct group of whales. The Archaeoceti, (Ancient Whales) They still had most of the things the same as land mammals but their limbs reduced in size and front limbs were paddle shaped.
The oldest member of the group Archaeocetes (Ancient Whales) was the Pakicetus.
Modern Whale Adaptations
The skeletons of both land animals and whales were clear, with the hind limbs basically disappeared. The pelvic bone is not attached to any bone. The front limbs in the whales still contain the bones that are in the front limbs of land mammals.
With whales having no fur at all it helps them with swimming because if they had fur it would drag. Land mammals have a form of fur used as insulation. With the whales loosing the fur they now have this streamlined body, for insulation they have blubber, a thick layer of it to be exact, under their skin. The blubber helps the streamline with holds the energy storage and protects whale from heat loss.
Whales have developed a system to breathe and get enough oxygen, since they spend most of their time in the water. When breathing for humans they exchange more than 12% of lung volume, but land mammals are beaten by whales with them being able to store more oxygen in its muscles. Plus, their blowholes are on top of their head which makes it easier to breathe.
Big Blue Whale Photo
Evolution of whales
The mystery behind their evolution
Nowadays we have the technology to search up the several factors that the ancestors of whales began with, for instance their need to breathe. The designs of their spines were made for running not swimming.
Their fin bones resemble their land ancestors limb bones.
Scuba Diver with a Big Blue Whale
Pakicetus
Basilosaurus
Big Blue Whale
