Hi, need to submit a 500 words essay on the topic Phylogenetic relationships of a group of organisms.
Phylogenetic analysis by means of cladistics uses shared and derived characteristics as the only criteria for grouping within a genus or species. A shared character is the common feature for all the species being evaluated and a derived character is a feature that evolved only within the group being studied.
The hypothetical cladistic analysis will include an organism which is distantly related to the organisms within the group being studied. In the example, this organism is known as the out-group and serves as the starting point for comparison with the other organisms being evaluated. In our example, the earthworm represents this out-group. The other organisms in the group are an eel, a salmon fish, a Lizard, a Turtle and a Lion. In the character table, the organisms are placed sequentially in a row and their characteristics are listed in a column on the left (Table). A character lacking in an organism is scored as ‘0’ and the presence of a particular trait is scored as ‘1’ as shown in the Table.
When the characters or traits are displayed in the form of a tree, it represents the cladistic hypothesis of the evolutionary relationship between the organisms under study. The tree showing the above cladistic analysis is as follows:
Although a cladogram does not indicate the strength of a derived character or even its evolutionary importance, it does emphasize the sequence in which the derived characters arise from a central phylogenetic tree. In the above example, the earthworm lacks all the listed characteristics while the lion which is at the top of the evolutionary ladder in this analysis possesses