Cavity and solid walls. 1  A cavity wall is made up of two walls with a gap in between, known as the cavity; the outer leaf is usually made of brick, and the inner layer of brick or concrete block.  A solid wall has no cavity; each wall is a single solid wall, usually made of brick or stone.
A cladogram (from Greek clados branch and gramma character) is a diagram used in cladistics which shows relations among organisms.
Cladistics is a powerful modern tool for studying and understanding evolution. Cladistics attempts to do for the entire history of life what genealogy does for the history of human families: to disentangle the relationships between all living beings. But while genealogy focuses on detailed lineages of ancestry and descent, cladograms focus on identifying the common ancestry of related groups. This cladogram represents the archosaurs, the common ancestors of crocodilians, birds, and all their descendants.