Dragonfly
The dragonfly is an insect with two pairs of transparent wings and an enlongated body with three distinct parts. They have six legs but most dragonflies can not walk well on them. They feed on mosquitos and other tiny insects. Dragonflies come from the order of Odonata. Their wings make them one of the fastest insects in the world.
Butterfly
The butterfly, like the dragonfly, also has two pairs of wings but instead of being transparent, they are covered in colorful scales. They have an elongated body with three parts, six legs, and they sip on nectar with their long tongue for food. Butterflies come from the order Lepidoptera. They are good fliers but can only fly if the temperature is above 86 degrees.
What is the Homologous trait?
In this example, the homologous trait would be the wings of both the dragonfly and the butterfly. Even though they serve the same purpose, they have completely different structures. A dragonfly's wing is transparent. There are very few veins in the wings as well. They are straight out and do not move well, meaning not flexible. But, because of their wings, they are able to fly sideways, backwards, make sharp turns, and even hover with ease. A butterfly's wings on the other hand are completely different. Their wings possess scales which give it their vibrant colors. Their wings have many veins and that is what keeps them warm enough to fly. Unlike the dragonfly, a butterly has a pair of forewings and hindwings. These do not stick straight out, they are attached to the thorax segment of their body and are flexible. So, the anatomy of both insect's wings are completely different yet provide the same service and purpose. This is a homologous trait.
Who is the common ancestor?
The common ancestor between the dragonfly and butterfly would be the insect. Even though a dragonfly is in the Odonata order and the butterfly is from the Lepidoptera order, they both are derived from arthropods which eventually evolved into insects. Not all insects have wings, but all insects have an exoskeleton, 3 part body, jointed legs, and antennae. So dragonflies and butterflies have evolved from the same common ancestor.
Analogous Trait: Dorsal Fins
Shark
A shark is a big fish with no bones in it's body. It only has cartilage. It lives in the ocean and has up to 3,000 teeth at one time, replacing themselves if lost. A shark has 8 fins, are cold blooded, and are covered in scales that point towards the tail. They breathe through their gills by inhaling water. Sharks can't chew their food so they have to rip the flesh and swallow whole, which is why sharks do not have to eat as often as other animals. They can smell blood from miles and miles away which gives them a huge advantage since they mostly live in open water.
Dolphin
The dolphin is a marine mammal. This means that dolphins are warm blooded and breathe air through a blowhole located on the top of their head. They possess 2 pectoral fins, a dorsal fin, and a fluke (tail). These are used for fast swimming. Dolphins do not have any hair, unlike other mammals. They are known for being extremely intelligent animals and live in large pods together. They communicate by very loud frequency calls that are unique to each dolphin.
What is the analogous trait?
The analogous trait shared by the shark and dolphin would be the dorsal fin. Both the shark and the dolphin possess dorasal fins. They are both made of cartilage and not bones. The structure is the same and they are both used for the same thing which is to stablize the animal in water while it swims along with assisting turns. Although the shark is a member of the fish family and the dolphin is a mammal, they both have a common analogous trait of a dorsal fin even though they have not evolved from the same common ancestor.
Did the common ancestor possess this analogous trait?
It does not seem that the common ancestor of a dolphin and a shark shared this analgous trait. It is hard to determine if dolphins simply stayed in the water while other mammals eventually migrated out of the water or if dolphins and whales migrated to the water away from land. Since the shark has evolved from a fish which has always had dorsal fins and dolphins are from the mammal family which are not normally in teh water, it is safe to say that the common ancestor of sharks and dolphins did not possess this analogous trait.
This was an interesting set of homologs. My only concern is that I'm not sure that they are homologous because you didn't confirm that their ancestor had wings and passed the trait onto both organisms. If they arose independently of the common ancestor, that would make these traits analogs. It would be interesting to confirm this one way or the other.
ReplyDeleteGood work on the analogous trait. You are correct that these traits arose independently from each other, though to answer your question, dolphins and whales started as land animals and made their way into the water. Nice work on this section.