Evolutionary tree

The Evolutionary Tree

1

2

3

4

The evolutionary tree above represents the relationships between lobsters, fish, humans, birds, and lizards. All the organisms share a common ancestor and belong to the kingdom Animalia. The branches were numbered for explanation purposes. Different animal characteristics, such as skeletal structures and other physical properties, were considered.

From the common ancestor, the organisms branched into two broad groups based on a backbone’s presence. At this stage, lobster, which is the only invertebrate among the organisms separated from the other group constituting birds, fish, lizards, and humans, which are vertebrates. In addition to this, their entire skeletal system was considered. While lobsters lacked bones, all the other organs had a well-developed skeletal system consisting of bones. The skeletal system of lobsters consists of an external exoskeleton. The other factor considered in the first branch is the existence of a developed nervous system. All the organisms except the lobster have a good network of nerves that make up the nervous system.

In the second branch, different factors were considered. One, all the animals except fish are terrestrial. This difference in habitat resulted in a difference in their respiratory systems. Fish, which is aquatic, uses gills for gaseous exchange while humans, birds, and lizards have well-developedrespiratory systems consisting of lungs, airways and blood vessels. Besides, humans, birds, and lizards have limbs with digits (fingers and toes) while fish does not. Fish uses fins to swim while humans, birds, and lizards have developed limbs for locomotion. The other difference considered in the second branch is the mode of fertilization. In humans, birds, and lizards, reproduction of the female gametes occurs inside the body of the organism, while fertilization in fish is external. In fish, the female lays unfertilized eggs inside the water, and the male fish of the same species fertilizes them. However, some fish species exhibit internal fertilization giving birth to young fish. In the other organisms, the males mate with the females, leading to the female gametes’ internal fertilization without an option for external reproduction. The other factor considered was the nature of cells that lead to the production of scales, skin fur, and feathers. In fish, the cells that produce scales are completely different from the rest of the animals. The cells responsible for the development of scales, fur and feathers are similar in humans, birds, and lizards.

In the third branch, several characteristics were considered. The main one was the presence of scales in both lizards and birds. In humans, the body is covered with skin and fur. The other difference arises in their mode of reproduction. All the animals except humans reproduce by laying eggs, which undergo incubation before they hatch into young ones. Humans, unlike lizards and birds, have mammalian glands. They breastfeed their young ones while lizards and birds do not. Finally, while humans have large developed brains, birds and lizards’ brains are inferior. The final branch (4) arises from the physical differences between birds and lizards. While both have scales, birds have their bodies covered with feathers while lizards do not. The other striking difference between birds and lizards is that lizards are poikilothermic, while birds are homoeothermic. From the above evolutionary tree, lizards and birds are more related to humans than fish and lobsters because they share a common ancestor at branch 3. Finally, the most related organisms are birds and lizards because they share the latest ancestor.