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, also known as phylogenetic systematics, is a relatively new way of doing systematics. It works by analysing different taxa to find objective similarities and differences between them, and using those similarities and differences to derive a hierarchical structure showing which taxa are most similar to others.