Today, eutherians have effectively outcompeted its fellow mammals marsupials and monotremes for ecological niches. They are found in virtually every part of the world native to Europe, Africa, Asia and America, including oceans. Monotremes and marsupials are mostly found in Australia and New Guinea only (Archibald, 2001). The ability to outcompete fellow mammals is characterised by their method of gestation where they foster their young within the mother’s body by the placenta, allowing nutrients, oxygen and excretory exchanges between young and mother with the help of umbilical cord (Smith, 2015).This enables greater maturity and development of the young when born, increasing their chances of survival. Furthermore, eutherians lack epipubic bones (which are present in monotremes and marsupials), which allows prolonged expansion of the abdomen during pregnancy (Tarver, 2016). On the …show more content…
However, they began to go extinct when North America merged lands with the Southern counterparts, allowing placentals to move into South America and largely outcompete them (Moskowitz ,2010). Placentals now occupy one of the widest range of environments from marine to terrestrial. In order to thrive in the environments they are subjected to, eutherians have evolved various structural adaptations. They vary in size from shrews to whales. Being housed largely in tropical Asia, shrews (Eulipotyphla) are terrestrially adapted to dig burrows to hide from predators and forage for food with their reduced body size. In contrast, whales (cetacea) are the largest creatures dominating deep oceans. With its enlarged body size, its stomach is able to contain one tonne of krill for feeding (WWF, 2016). Contrastingly, the marsupials like kangaroos and koalas, as well as monotremes including the duck billed platypus and spiny anteater, all remained and possesses similar body sizes, completely lacking diversity compared to the
3 Apr. 2014. The 'Standard' of the 'Standard'. http://eol.org/pages/323582/details>. Evans, Arthur V., Rosser W. Garrison, Neil Schlager, and Michael Hutchins. Grzimeks' Animal Life Encyclopedia.
Lerner, E. and Lerner, B., 2008. Giraffes and okapi. The Gale Encyclopedia of Science 4
Manatees, commonly called Sea Cow, are large aquatic mammals that are found in warm coastal areas, rivers and warm water springs in the Amazon Basin, West Africa, the Gulf of Mexico, the Caribbean Sea and the Southeastern United States. Manatees can be found in salt water, fresh water and brackish water. They spend most of their time eating aquatic plants, resting, migrating and nurturing their young. The manatee species has evolved over the last 45 million years. The adult manatee evolved into an average of approximately 10 feet long and weighs between 800 and 1,200 pounds (Site This).
Today, we see much less of an obvious relationship of the cetaceans to the terrestrial mammals.
Community ecology Sea otters predate many herbivorous invertebrates, including sea urchins. Sea urchins feed on kelp forests, which are an important habitat for fish and other marine organisms. A high population of sea urchins has an adverse effect on kelp forests. Since sea otters predate sea urchins, their populations are kept in check.... ...
Orcas, or killer whales are majestic giants of the sea. They are actually the largest type of dolphin. They have long black bodies with distinct white patches near their eyes. A killer whale can be up to 32 feet or more in length, and weigh up to 12,000 pounds. Females are a bit smaller, but live longer (Gorman). The name “killer whale” apparently came not because it is a vicious whale, but because it preys on whales. They do not have any natural predators, and they are considered the “top dog” of the ocean. Not even the great white shark stands a chance against these superb killers. “Unlike sharks, killer whales are cautious hunters, sometimes spending hours harassing a 1,000-pound sea lion so it can easily be drowned” (Francis). Orcas use many hunting tactics that are unique to their species, which is what makes them invincible.
Jefferson, T. A, M. A. Webber, and R. L. Pitman. (2008). Marine Mammals of the World, A Comprehensive Guide to their Identification. Amsterdam, Elsevier. p. 241-244.
David Attenborough’s The Life of Mammals: Meat Eaters and Steve Irwin’s Africa’s Deadliest Snakes are wildlife documentaries that have similar yet different purposes. Attenborough’s has a script that is rehearsed and the natural environment is followed. Irwin’s does not have a script and the animals are picked up. However, both hosts inform the audience of the animal and how they function. Attenborough achieves this through the use of language and Irwin achieves this by being a presenter. Purpose, audience, context, language and form will be compared between the two texts.
The Platypus (Ornithorhynchus anatinus) is a unique animal that is found only in Australia. It is in the class Mammalia and the order Monotrema. Monotremes are phylogenetically the oldest of the mammals and can only be found naturally in Australia and in nearby New Guinea. They are quite different from placentals and marsupials and are believed to be the link between the reptiles and the other mammals. This is most noticeable though their means of reproduction and waste elimination. Montremes have a cloaca, which is a single opening for passage of solid and liquid waste, where the transfer of sperm takes place, and in females, the laying of eggs. This feature is shared only with birds and reptiles.
The Humpback Whale, Megaptera novaeangliae, is part of the marine mammals group. They are found in oceans all over the world, they live in open waters. Even though they are mammals, they do not live on land (Monterey Bay Aquarium). Humpback whales are known for their magical song that can travel great distances. These gentle giants are omnivores, their main diet is krill. They are mostly found near coastlines feeding on tiny shrimp-like krill, plankton and small fish. Humpbacks migrate annually from summer feeding grounds near the poles to warmer winter breeding water closer to the Equator. Humpback whales are powerful swimmers, and they use their massive tail fin, called a fluke to propel themselves through or even out of the water! Mothers and their young swim close together, often touching one another with their flippers with what appears to be gestures of affection. Even though it takes more than one year for a humpback whale to grow fully, mother whales leave them after one year (National Geographic).
The defenition of a monotreme is an unusual mammal that lays eggs instead of giving birth to live babies. A few examples are the echidna and the platypus. Their skulls have certain features that resemble reptiles. They have three bodily systems, they have the digestive system, urinary system, and reproductive system. These systems all end up in the same chamber for monotremes called the cloaca. Cloaca means “one hole’’ so it fits perfectly with the monotremes situation. After monotremes give birth they suckle their young after hey hatch out of their eggs. They also have bones like the marsupials called eupubic bones that are connected to the pelvis. The baby monotremes have teeth but they do not go through their gums and real functional teeth are not shown in the adult monotremes.
The fossil record of horses extends back to an odd-toed ungulate mammal belonging to the taxonomic family Equidae, a dog-like ancestor 55 to 42 million years ago in the genus Hyracotherium in North America. Hyracotherium had a primitively little face , four-toed forefeet, three-toed hind feet, an arched back, small brain, and higher hindquarters than forehand. Later genus has increased in body size, brain complexity, the size of cheek teeth, lengthening of the face, and reduction of toe number. However, even though horses got larger over time but these trends are not seen in all of the horse lines. Genus such as Hipparion existed from 23 to 2 million years ago, showed gains in size, But some later genus such as Archeohippus, and Calippus got smaller again (Boundless, 2016),(Encyclopedia of Life,2015), (equineworld.co.uk, 2014), (Molen, M.
The first hypothesis proposed that “mammal abundances are negatively correlated with levels of radioactive contamination at Chernobyl” (Deryabina et al., 2015). To test this hypothesis, the researchers conducted censuses of the large mammal populations by observing tracks in fresh snow along walking routes. The track surveys were conducted shortly after snowfall on a single day in February with only fresh tracks counted, counting the number of tracks of each species on each route with a total distance of 315 kilometers and an average track length of nine kilometers. This method of data collecting did not provide absolute density information of the mammal populations, but provided data on relative mammal activity. The researchers compared average track counts per ten kilometers to compare different routes within the reserve in terms of animal activity.
On this endanger earth, there are numerous of endangered species. Blue whale are specified as the largest animal that lived on earth. It is one of the endanger species listed on the Wildlife Services website. Their size are around 82 to 105 feet long. To further discuss about this typical endangered species I will research and analyze on this paper.
Sikes, Roberts. and William L. Gannon. "Guidelines of the American Society of Mammalogists for the Use of Wild Mammals in Research." Journal of Mammalogy 92.1 (Feb. 2011): 235-253. Academic Search Premier. EBSCO. Web. 5 Oct. 2011.