River dolphins have been an elusive group of cetaceans, taxonomically and biologically, since the time of their first noted observation in the wild. They are proven to have oceanic ancestors which invaded the riverine systems on at least three independent events and hence develop ecological extreme specialization to adapt to the freshwater environment. Although this hypothesis has been challenged, invasion of the freshwater systems might have insured their survival against either competitive exclusion by more recent and better adapted smaller cetaceans or changing physical parameters of the oceanic systems. (Cassens, 2000; Geisler, 2011) (reversal of this may happen due to deteriorating habitat?) Direct habitat sharing combined with the degradation …show more content…
Evidence suggests that early Odontocetes invaded the freshwater river systems at least three times, diverging completely during the late Oligocene to early Miocene period. Although contentious, there is a possibility of Iniidae, Pontoporiidae and Lipotiidae being monophyletic and thus a yet older invasion of the riverine habitat than the very first divergence is suggested. However invasion of the riverine environment by the most recent common ancestor does not correlate the current distribution of species with that of tectonic plate movements. Hence, based on these observations and the phylogenetic analysis a minimum of three independent invasions of the freshwater habitat are suggested (Cassens, 2000). -- Hamilton et al. expanded upon the hypothesis of separate, freshwater invasions by speculating that the ancestors of extant river dolphins remained in river systems after sea level regressed from its middle Miocene highs (Geisler, 2011; Hamilton, 2001) -- it is possible that the intensity of competition, not the simple presence or absence of a single delphinoid species, could explain the absence of close relatives to Lipotes and Platanista in modern marine environments (Geisler, …show more content…
hypothesize that the two species of Platinistidae emerged in the larger Ganges-Brahmaputra River system, moving towards the adjacent Indus River system around 0.5 - 0.6 mya, being reproductively isolated since 0.55 mya when they shared a common ancestor, at a time when the two systems were loosely connected by a few tributaries (Braulik, 2015). This is supported by studies that show from 5 mya to 0.3 mya, major tributaries of Ganges in Punjab were gradually re-routed into the Indus (Clift and Blusztajn, 2005). Since the populations in these river systems are separated by hundreds of kilometers of landmass, dispersal between the river systems and contemporary genetic exchange is deemed very unlikely and although these dolphins are occasionally sighted in brackish water, their dispersal between river systems through the ocean would involve a highly improbable journey through exposed saline waters, of at least 4,600 km around the Indian peninsula (Braulik,
Martin is confident that the extinctions must have been caused by “something outside the normal experience of mammals.”
The article Poor Teeth was written by Sarah Smarsh with the goal in mind being to shed light on the issue between upper and lower class society in a particularly concrete way. Teeth and dental health are an easy thing for people to imagine in their head because everyone has a set whether they’re white and shiny or black and rotted. This makes it easy to draw a comparison between people that care for their teeth and those who don’t. However, access to dental knowledge and services which the lower class often times doesn’t have is very different between the poor and the rich. While the rich stroll through life showing off their perfect glossy white rows of teeth, there are less privileged people out there with barren mouths whose weak pale gums
Although it is remarkable that these marine mammals are capable of so much, there are things the public does not know. According to classified statistics, twenty-three out of forty-three animals died while being transported from their natural habitat to foreign aquariums for training. Another thing the public does not know is in reference to a similar marine mammal program in the Soviet Union. It has been reported that Soviet dolphins were trained to do "kamikaze" missions. Explosives were supposedly strapped to their backs and they were sent out to destroy enemy submarines. According to statistics, about two thousand dolphins have died on these, and similar, missions.
Cetaceans are thought to be some of the most intelligent species on this planet. Popular culture has embraced the idea of cetacean intelligence with shows such as the 1960s hit TV series Flipper, where a dolphin is used to help fight crime. In his comedic science fiction novels, the Hitchhiker’s Guide to the Galaxy, author Douglas Adams suggests that dolphins are the second most intelligent creatures on Earth, behind mice and above humans. Although most scientists would probably argue that humans are the most intelligent species, the behavior and brain size of dolphins and other cetaceans suggests that they too are intelligent. This paper will briefly describe the reason some scientists believe cetaceans are intelligent species and then give examples of scientific studies, which suggest cetacean intelligence. Since bottlenose dolphins and orcas are the most widely studied cetaceans, the survey of field studies will primarily focus on these two species. At the end, this paper provides an argument of why some scientists discredit the high degree of cetacean intelligence.
In Between all matters of life, communication between organisms of like species has been an important part of survival, for so long, and so perfect, that whales have not substantially evolved for about 33 billion years (Uhen, Mark). For example, dolphins hunt using a technique called ‘herding’,as well as many other techniques, which involves members of a pod circling a group of fish and through a series of yips, chirps, whistles, communicate to each other as they in circle their prey into a tightly packed group, allowing one dolphin at a time to swim through the group of fish while the other members of the pod incircle the fish. It is more efficient for groups of a like species to hunt together than one at a time (Bone, 2014). The herd will continue to do this until all have fed, or until the resourc...
2011 Revisiting Water and Hominun Evolution. In Was Man More Aquatic in the Past? Fifty
The order Lagomorpha consists of two extant families: Leporidae (hares and rabbits) and Ochotonidae (pikas) and several extinct families. The purpose of this paper is to identify the characterize biogeographical migration patterns of Lagomorphs and why. The natural geographical distribution today of the lagomorphs is found throughout Europe, Asia and North America. Figure 1 is an illustration depicting the various time periods as well as the number of million years ago (Mckenna 1997). The sources identified address the distribution throughout the Eocene to the Pliocene (35-5 Ma) (Figure 11). The aims of this paper are to identify the biogeographical distribution of the various families and how that compares to the modern day distribution.
[9] Deep sea and extreme shallow water habitats: affinities and adaptions by Franz Uiblein, Jorg Ott and Michael Stacowitsh 1996
Twenty-six years ago, the Delphinidae invaded planet Alvortia. The arrival of the unannounced visitors was met with a reception more deplorable than that of the death that lingered in the poignant future.
Rowat, D., and K. S. Brooks. 2012. A review of the biology, fisheries and conservation of the whale shark Rhincodon typus. Jour. Of. Fish. Bio. 80:1019-1056. (DOI:10.1111/j.1095-8649.2012.03252.x).
This finding, however, raises many questions about animal’s rights. In order for the scientists to get information on this new species they had to murder nine other whales, one ‘accidentally.’ This finding was a great feat for science because it is important to learn as much as we can about a species before they become extinct. The rate in which large aquatic mammals are reaching extinction has been rising. So although there is much to be found and much that has been found about not only the new species of the baleen whale, but also the other two species that have risen to the surface, it was not done without farthing along the extinction process of another species.
Lotze, Heike K., Marta Coll, Anna M. Magera, Christine Ward-Paige, and Laura Airoldi. "Recovery of Marine Animal Populations and Ecosystems." Trends in Ecology & Evolution 26.11 (2011): 595-605. Print.
...r. Even though they live in the ocean all their life and also amusement parks, dolphins are mammals, not fish. That makes them very intersting animals because of all the charactics that they have that people would have never known about. Dolphins are by far the most intelligant marine mammals in the ocean.
Did you know in the world there are more than 90 species of whales, dolphins, and porpoises? (WDC) The dolphin is a very important animal to the ocean and there are many different types to discover. In order to learn about dolphins, it is important to discuss where they live, their appearance, and what they eat. Some helpful words to understand are “dorsal fin”, a dorsal fin is the top pointed fin on the dolphins back, “flippers”, a flipper is a flat fin that dolphins use to swim, and “echolocation” is a tool dolphins use to find food by sounds bouncing off of objects (dictionary.com).