Use the following resources for background and to dig deeper into cladistics and phylogenetics:

• The Tree Room
  Understanding Evolution’s Tree Room project provides a thorough introduction to the interpretations, methodology, and applications of phylogenetics. You’ll also find a primer, interactive features, and teaching materials.
• The History of Life: Looking at the patterns
  This chapter of Understanding Evolution’s Evo 101 provides an accessible introduction to phylogenetics.
• OneZoom
  This website allows users to explore the Tree of Life clade by clade and branch by branch.
• Evolution, Investigating the Evidence
  Edited by Judy Scotchmoor and Dale Springer, The Paleontological Society, Special Publication, Volume 9, 1999.
  This book is an excellent reference for teachers and includes articles on the origins of life, phylogenetic reconstruction, geologic time and the fossil record, cladistics, evolutionary processes, rates, scales, and diversity, and an exploration of the conflict between modern science and some religious faiths.
• Life: A Natural History of the First Four Billion Years of Life on Earth
  By Richard Fortey, Vintage Books, 1999.
  This book provides a richly detailed and well-written account of the history of life on Earth, concentrating on how plants and animals evolved in their varied forms, their colonization of the land, plate tectonics and continental drift, mass extinctions and the diversification of mammals including the human lineage.
• The Book of Life: An Illustrated History of the Evolution of Life on Earth, Second Edition
  By Stephen Jay Gould (Editor), Peter Andrews, John BarberCon, Jean-Paul Tibbles (Illustrator), and Michael Benton (Contributor), WW Norton & Co., 2001.
  This book covers the breadth and minutia of life’s evolution beginning with origins and concluding with human impacts on the environment. This book will be a valuable addition to any teacher’s reference library.