Final answer:
A clade consists of an ancestor and all its descendants. In a cladogram showing the evolutionary relationships, mammals like rabbits and humans, along with lizards, are part of the clade Amniota, with mammals forming a more specific clade due to the presence of hair. Vertebrata represents a larger clade, inclusive of both Amniota and aquatic species.
Step-by-step explanation:
A clade is a group of organisms that includes an ancestor and all of its descendants, representing a single branch on the tree of life, based on shared evolutionary history. When we analyze a cladogram, such as Figure 20.10, we see that lizards, rabbits, and humans all descend from a common ancestor with an amniotic egg, therefore they are all part of the clade Amniota. Additionally, the presence of hair in mammals indicates they form a more specific clade within Amniota. As hair is a characteristic unique to mammals, and since they are included in Amniota, we can determine that hair evolved after the amniotic egg.
When looking at the largest clade in a cladogram, we refer to the most inclusive group stemming from a single point in the tree. This brings our attention to Vertebrata, which is a larger clade that includes fish, lamprey in addition to the Amniota group. Phylogenetic relationships, such as these, help us understand the complexity of evolutionary history and how current species are related back to their common ancestors.