Analogy + Homology

The connection between species throughout the world is inevitable- we're related. Whether it's through similar structures in the body, or functions they serve, the network exist. Specifically, homology links the world's species genetically.

Examples of Homology in Nature:

Humans and whales are connected through a few distinguishable traits. They both are mammals, one of land, one of the sea. Not only do they share similar attributes, such as nursing their young and socializing patterns, but they share bone structure.

Human 

Whale

It's easy to see the connection of the front limbs of these species. The bone structures are very similar, but have adapted to serve unique purposes. The human humerus and radius/ulna are longer in relation to their other bones to aid in lifting objects and reaching, as well as the development of an extra, quite useful phalanx, the thumb! The whale has much longer phalanges, to provide better movement and speed for swimming in the water. Both of these species have adapted to conform to the environment they are in for the purposes and duties they require to serve accordingly.

It's likely that both of these species adapted from a common ancestor of a placental mammal. We know this trait exists because other species the come from this ancestor also contain these structures within.

Though some structures may serve the same function, doesn't always mean that they are connected. Some species adapt similar characteristics to best serve their environment and not because they're related- making them analogous.

Examples of Analogy in Nature:

Two species that have analogous connections are dolphins and sharks. Though they live in similar environments and both use swimming as their source of movement, they have very different anatomical features. For example, dolphins breathe through their lungs, because they are mammals, where sharks breathe through gills, because they are fish. An easy way to recognize their differences is through the make up of the mammal "flipper" and the fish "fin". 

Fin

Convergence occurred because of these species need to evolve to the means of their environments. Though the internal structures may be different, their purpose and "look" are quite similar. For example, flippers and fins do not contain "fingers", (though flippers have phalanges) which wouldn't aid them in aquatic movement. Both of these structures help with their agility and, in  a sense, mode of transportation.

Flipper

Though sharks and dolphins share some kind of common vertebrate ancestor, WAY up the lineage line, these traits were not passed down via evolution. These traits were developed via a need for their function.