Final answer:
To classify an unknown animal, you would first inspect its body plan, particularly its symmetry, then analyze anatomical and developmental characteristics such as tissue layers and internal body cavity. Genetic data can also be important for classification. For phylogeny based on circulatory systems, organisms are ordered from the most primitive to the most advanced systems.
Step-by-step explanation:
Discovering and Classifying a New Species
When classifying an unknown animal, the first characteristic to look for is its body plan, specifically its symmetry. Symmetrical animals can be divided into roughly equivalent halves along at least one axis. After establishing symmetry, further classification can involve looking into the animal's morphology, which includes the number of tissue layers formed during development, the presence or absence of an internal body cavity, and features of embryological development like the origin of the mouth and anus or molting patterns. These anatomical and developmental traits aid in placing the organism into a particular domain and provide insight into its evolutionary history.
Another approach could involve examining genetic makeup, which can offer more concrete information for classifying the species, especially when the physical characteristics do not clearly indicate a relationship.
To construct a phylogeny of organisms based on circulatory system characteristics, the student would order the organisms in a way that reflects their evolutionary relationships, starting with the most primitive circulatory system to the most advanced. This ordering helps in understanding the evolutionary history of these species and their classification.