Physiological and Cultural Adaptations to High Solar Radiation.

 Shared Homologous Trait: Moles & Dolphins

The ideal environment for a Mole to thrive would be in wetlands, grasslands, and meadows, consisting of loose, movable soil in which they can tunnel into. They have also adapted to arid climates within deserts, and are known for their poor eyesight and excellent tunneling ability, creating approximately 160 ft. burrows overnight. All this digging requires strong arm and leg structures to push dirt to the sides and then behind them as they burrow. Meanwhile, being cetaceans of aquatic animals, Dolphins choose to inhabit warm coastal bodies of water and can swim up to 62 miles per day at an average of 31 mph. They, too, require strong arm structures to steer themselves and come to a stop while swimming at high speeds. During intense chases from predators, dolphins can easily turn and redirect their movement because of these front fins.

It's easy to write these two species off as entirely unrelated, seeing as moles are from the Eulipotyphla branch of mammals and dolphins stem from the Cetacean branch. However, the homologous forearm structures between the two show the ancestral link between the two, which would be the Eutherian (placental) mammal. This mammal hails from the late cretaceous period and is the ancestral link for a variety of mammals such as seals, beavers, and shrews. Almost all animals in this group have the same or similar forearm structures consisting of phalanges, carpals, metacarpals, etc. While the Cetacean and Eulipotyphla diverged on a grand scale to different environments, we can still see these similarities from their common shared mammalian ancestor to this day.

The anatomy of these two species is quite different, both physically and genetically; however, looking at the range of motion both have in their front limbs, you can see the shared dexterity. While dolphin fins have phalanges, they are covered by a thick layer of flesh with no individual digits, unlike a mole, which has access to each individual digit. Both, however, have phalanges to elongate their limbs and metacarpals for range of motion for precision with swimming and digging. Following this comparison up the limbs, we can see that the carpals are also in similar locations and allow the connecting points of the phalanges and arm bones to rotate, allowing for more control. The arm bones themselves are similarly structured (humans share these structures as well as many other mammals), the radius and ulna being present allows both species to change their direction, shift weight as they crawl or swim, and move water and dirt to travel. Lastly and most powerfully, the humerus of the Dolphin as well as the Mole share similar placement and structure, being the main weight-bearing bone within the front limbs. The combination of these shared arm structures shows the genetic ancestry shared between these species and the fact that, despite their different environments, they have been able to utilize the same features for different evolved traits. 

Shared Analogous Traits: Echidnas & Anteaters

Echidnas can be found throughout Australia and New Guinea, preferring the dry climate, brush, and forests. Their direct diet consists mostly of insects, especially colony insects such as ants and termites, using their long tongue to take hold of their prey and draw it into their long snout. Similarly, the Anteater, which hails from Central and South America, also uses a long, curved, textured tongue to draw ants, beetles, and termites out of colony holes and other hiding spots and into its snout. Both of these species use a long tongue and snout to extend into the recesses of small crevasses and colony holes of termites and ants to find food. This connects them through an Analogous trait, which we will expand upon.

Looking back far enough, the echidna's ancestor, the “Kryoryctes Cadburyi”, does share some common ancestor with the modern anteaters “Pro Tamandua”; however, the similarities in environmentally evolved snouts and tongues are simply survival-linked and do not come from their ancestral lineage. This in itself makes the shared trait analogous rather than homologous, as the monotreme Kryoryctes Cadburyi was more closely compared to an aquatic-dwelling platypus than a land mammal. The egg-laying nature of this species is described as Monotremata and differs greatly from the Xenarthra Placental mammals that the anteater evolved from. While classified as a mammal, it lays its offspring as eggs, while the other gives birth to offspring, much like humans and other placental mammals. 

The formation of the long snout of the anteater came from the evolutionary pressures and natural selection of the individuals within the species, not being limited to large prey crawling on the ground, but rather being able to follow an entire insect colony back to its source, increasing its chances of survival. Much like this, the echidna's evolutionary process took place in far more tropical climates where much of the insect biodiversity on the planet can be found. With this large influx of insects comes a large variety of birds, mammals, and reptiles that will seek them as a food source, making the environment fairly competitive. This competition fueled the genetic preference for a long snout and tongue to find insects in tree logs, ground colonies, rocks, and other crevice-containing vessels that would be difficult with stubby, inflexible snouts and beaks. The flexibility of these snouts is also a very advantageous feature of both the Anteater and the echidna's snouts, which diversifies them from their ancestors. Both adapted to portray this visual and genetic similarity on different continents, and while they eat similar foods and share similar visual traits, they stem from different branches of mammals and did not carry the trait homologous but rather, Analogously.

Research References:

Comparative Anatomy as Evidence for Evaluation. 

www.labxchange.org/library/items/lb:LabXchange:acfccc5f:lx_image:1

“Dolphin Physiology - Dolphin Research Center.” Dolphin Research Center, dolphins.org/physiology.

Echidna | San Diego Zoo Animals and Plants. animals.sandiegozoo.org/animals/echidna.

“Facts About Dolphins.” World Animal Protection Aoteroa New Zealand

www.worldanimalprotection.org.nz/education/animal-facts/dolphins.

Smithsonian’s National Zoo and Conservation Biology Institute. “Giant Anteater.” Smithsonian’s

National Zoo and Conservation Biology Institute, nationalzoo.si.edu/animals/giant-anteater.