Will the sea lion or the dolphin be more hydrodynamic, based on their body form, external appendages, and body covering?
The dolphin has a higher hydrodynamic coefficient than the sea lion. Sea lions, which are pinnipeds, have feathers and were converted from land mammals, while dolphins are hairless. When swimming, fur can cause drag. Dolphins, which are cetaceans, are propelled by their tail fins. All cetaceans’ primary propulsive motions occur in the vertical plane, and this method of propulsion is shared by other fast-moving fish such as tuna. Sea lions drive themselves into the sea with their long front flippers. Dolphins have a spindly body that is more compact than sea lions’. The more streamlined the body, the lower the pressure drag of the swimmer (Perrin, Würsig & Thewissen 1140).
How does the direction of tail orientation in cetaceans compare with that of fish?
A fish’s tail is vertical and moves side to side. A cetacean’s tail is horizontal and moves up and down (Fish or Cetacean…Can You Tell the Difference?)
How do you think the fact that cetaceans’ flukes are oriented the way they are relates to their air-breathing behavior?
Cetacean’s flat tail fluke, composed of fibrous tissue moves vertically through water. The fluke functions as a dive plane, acting with the cetacean’s flippers to control body orientation (Norris 258). Since cetaceans inhale at the beginning of a dive and their blowhole closes tightly while doing it, the flukes vertical orientation helps cetaceans dive in order to surface and exhale through their blowhole
Because the heat produced by the volume of the muscles and other internal organs of the marine mammal is lost to the water through its surface area, or skin, which whale, a baby or its mother – will have the greater heat loss to the water, pound per pound?
A mother whale will have the greater heat loss to the water because one way of minimizing heat loss is to have a relatively low surface area-to-volume ratio (Ballantyne). The smaller amount of skin of a baby whale generates more heat. Small body size of marine mammals incur additional heat management (Hoelzel 261).
Of a thousand baby whales, which will have a better chance of building those body parts with their mother’s milk, instead of using the energy in her milk just to stay warm, the largest babies or the smallest babies?
The largest baby whales will have a better chance of building body parts with their mother’s milk. Very small marine mammals rely on high metabolic heat production to sustain their body temperature during exposure to cold or in the water. Smaller babies require more energy from their mother’s milk to keep warm in the water, so their mother’s milk is used for both building body parts and keeping warm.
Is the size of a mammal an inherited trait?
There is an inherited genetic make-up that is attributed to size of mammals. However, the size of an animal can also be attributed to its need to adapt to its environment. So the size of a mammal can be attributed to its inherited trait and its need to adapt to its environment.
Use your answer to questions 5 and 6 to help explain the large size of marine mammals.
Marine mammals can’t be too small because the surface area to volume ratio of the body reduces heat loss. They can’t be too small because they will lose heat faster than they produce it. Because water transports heat faster than air, sea-faring mammals have to be much larger to survive—at least 80 pounds. That’s how warm-blooded marine mammals have adapted to their environment.
Once again, remembering how size affects an organism’s surface area-to-volume ratio, will the whale or the dolphin have to put out more energy, pound per pound, to attain the same speed in the water?
The strength of a marine mammal’s muscles that they use for swimming is determined by its volume, but the frictional resistance is related to the animal’s surface area. The fastest marine mammal, the dolphin, has large bodies and small flippers, which reduces the ratio of surface area to overall body mass. The reason why they have a larger body mass is because they must expend more energy to swim fast.
What relationship can you suggest between the presence of blubber layers and homeothermy?
The presence of the blubber layers provides insulation, food reserve, and aids with buoyancy. Blubber is an excellent heat insulator. It has been found that the heat conductivity of blubber is very low and heat transfer occurs at a very slow rate. Only 10 percent of all heat loss of the body takes place here (Hovinen, Faber & Goh).
How might blubber be used by marine mammals to improve their hydrodynamic efficiency?
Blubber affects buoyancy and functions as a body streamliner and elastic spring for efficient hydrodynamic locomotion. Blubber functions to maintain both water balance and energy metabolism (Perrin, Würsig, & Thewissen 118).
Position of nostrils
Middle part of the face, protruding
Protruding in front of its face; four nostrils
Middle part of the face, protruding
Front of the face
General shape of mandibles
Rounded, short muzzle
General shape of maxillary bones
Diamond shaped; vertical
Their eyes and nose are near the top of their head so they can stick them out of the water easily.
The mandibular symphysis is in the anterior region where the two mandibles join. The two mandibles are joined with a bony suture and/or connective tissue that holds the two mandibles together.
Relative size of cranium
What value is it to the pinniped to still have its nostrils on the front of its face, like a terrestrial mammal?
-Since pinnipeds are amphibious mammals, its anatomical structure has a wide range of adaptations for living in land and on water. Once underwater, pinnipeds have no virtually no sense of smell because their nostrils are closed tightly, and they have a limited sense of taste. However, once they are out of the water and on land, they have an acute sense of smell. Their nostrils voluntarily open when they surface out of the water.
Ballantyne, Coco. “How do marine mammals avoid freezing to death?” Scientific
American. 2017. www.scientificamerican.com/article/marine-mammals-cold-avoid-freezing-death/. Web. 17 April 2017.
Barroso, Celia. “Shape Analysis of Odontocete Mandibles: Functional and Evolutionary
Implications. San Diego State University.2010. sdsu-dspace.calstate.edu/bitstream/handle/10211.10/430/Barroso_Celia.pdf?sequence=1. Web. 16 April 2017.
“Fish or Cetacean…Can You Tell the Difference.” www.ccaro.org/c-fish-or-
cetacean.php. Web.17 April 2017.
Hoelzel, A. Rus (ed.) Marine Mammal Biology: An Evolutionary Approach. 2002.
Blackwell Publishing, Oxford. books.google.com.ph/books?id=OwF05MfTagsC&pg=PA261&dq=marine+mammals+body+size&hl=en&sa=X&ved=0ahUKEwi4nufAjcHTAhWBNJQKHSuxCFoQ6AEILTAC#v=onepage&q=marine%20mammals%20body%20size&f=false. Web. 17 April 2017.
Hovinen, Bradford, Faber, Onno, and Goh, Vincent. Dolphins The Oracles of the Sea.
1998schoolnet.org.za/PILAfrica/en/webs/17963/thermoregulation.html.Web. 16 April 2017.
Norris, Kenneth Stafford. Whales, Dolphins, and Porpoises. 1977. University of
California Press, Berkeley.
Perrin, William F., Würsig, Bernd & Thewissen, J.G.M. (eds). Encyclopedia of Marine
Mammals. 2008. Academic Press, Burlington Massachussetts.