Analogy/Homology

Dolphin Flipper vs. Human Arm/ Hand

a. Two different species that posses the homologous trait are dolphins and humans. The dolphin flipper and the human arm/hand have similar structures.

b. The dolphin flippers act as stabilisers and are used for steering, while swimming, and can act as brakes, along with the tail. They are made of collagen- rich connective tissue, that are very similar to the bones inside a humans arm and hand. The joint that is comparable to the elbow is located at the body surface. The humerus has a large- globular head where it meets the scapula in the shoulder joint. Arteries in the flipers are surrounded by veins. So, some heat from the blood traveling through the arteries is transferred to the venous blood. This countercurrent heat exchange aids dolphins in conserving body heat. To shed excess body heat, circulation increases in veins near the surface of the flippers and decreases in veins returning to the body core.

The humerus articulates with the scapula at the shoulder and with the radius and ulna at the elbow. It is a long bone that is essential for movement and support of the arm. The brachial artery travels most of the bones length. The brachial artery branches into several arteries, distributing oxygenated blood from the lungs and heart. The hand exhibits great mobility and flexibility in the digits and in the whole organ. The complex abilities of the hand are part of what makes humans unique. The hand gives us a forceful grip and we use our hands the most out of anything else on our body.  The structures are different between dolphins and humans because the human’s arms are much longer than a dolphin’s flipper. Also, humans a more vertical and dolphins swim more horizontal.

c. The common ancestor of dolphins are Pakicetus. We know this because its legs are shorter, and its hands and feet are enlarged like paddles. Its tail is longer and more muscular, too. The ear region of the skull resembles fossil and modern whales, and the teeth and other features are similar to those of some fossil whales. Whales and dolphins come from the same common ancestor. The common ancestor of humans is the Chimpanzee. Shoulder shape tracks changes in early human behavior such as reduced climbing and increased tool use. Chimpanzees are the closest living relatives to humans.

d.               

Bird Wing vs. Bat Wing

a. Two different species that posses the analogous trait are birds and bats. I chose the wings on a bird versus the wings on a bat.

b. Bird and bat wings are analogous because they have separate evolutionary origins, but are superficially similar because they evolved to serve the same function. Bird wings and bat wings are analogous as flight structures: their structure and function have evolved by different routes from a flightless reptilian ancestor. A good portion of the flight surface in bats consists of a membrane stretched between the extended digits in the hand, whereas the digits of the bird are relatively small and do not support the flight surface. Birds have the same arm bones as humans and bats, but the bones are arranged in their wings very differently than the bones in bat wings. Bird and bat bones look small and delicate. This was thought to make both bird and bat bones lighter so they can fly.

c. The discovery that birds evolved from small carnivorous dinosaurs of the Late Jurassic.  The common ancestor of bats Laurasiatheria; which is a superorder of placental mammals. Because Laurasiatheria is defined by DNA sequence analysis, the group does not share any obvious anatomical features. So, this branches into categories. Bats are mammals in the order Chiroptera. They are the only mammals that can fly. In these categories also include carnivores. Bats and birds are not genetically related because the structure in their wings and the way they fly are fairly different. Birds have more gaps and feathers in their wings to help them glide through the air whereas bat wings don’t, so it seems as they are swimming through air.

d.