Final answer:
Systematists include multiple characters to create phylogenetic trees that accurately reflect evolutionary relationships, using principles like maximum parsimony to determine the simplest evolutionary pathways. These trees are continually updated with new information, such as molecular data and fossil records, to maintain an accurate representation of the tree of life.
Step-by-step explanation:
Systematists use more than one character when reconstructing trees because phylogenetic trees are based on evolutionary connections, and using multiple characters provides a more robust and accurate representation of these connections. Homologous characteristics, which are traits inherited from a common ancestor, are particularly useful in constructing these trees. However, analogous characteristics, which are similar due to convergent evolution rather than shared ancestry, may also be relevant in some cases.
To ensure the phylogenetic tree reflects the simplest explanation for the observed characteristics, scientists use a principle called maximum parsimony. This principle favors the tree that requires the fewest evolutionary changes. When constructing phylogenetic trees, inconsistencies, such as shared derived characters that do not appear in all members of a clade or characters that appear to have evolved independently in different clades, must be carefully evaluated. Computer programs aid in analyzing complex data to find the tree that best fits the maximum parsimony principle.
Through ongoing research and discovery, the "tree of life" is continually refined. As new information about living things is gathered, from molecular data to fossil records, the phylogenetic tree is updated to best represent the evolutionary histories of organisms. This comprehensive approach helps scientists decipher the complex web of life on Earth, ensuring that the tree of life remains an accurate tool for understanding biological diversity and evolutionary relationships.