BIOLOGY 160 question on phylogenetic trees. Help!! Please?

the tree is organized into lineages. There is a common ancestor and the branches that stem from that ancestor are the descendants. The way the biologists are able to place species on a tree and draw these lineages is by the use of qualitative traits and and quantitative traits. Qualitative traits, like the fur are used to group species. For example, after a certain time, fur became evident in the fossil record. Using this information, scientists can then say that any species in this lineage after this time has fur. The quantitative traits like genes are used to group species. If they found 5 unknown animals, they could test for the same gene in each animal to determine if each animal was a member of the same species. They could then use this trait like the fur. I hope this explanation helps...Its really hard to explain this without drawing it. just search "phylogenetic trees" online and you will get textbook pictures that may make more sense