BiblioVault may have an electronic file which would meet your requirements for this title:
Animals Without Backbones: An Introduction to the Invertebrates
Ralph Buchsbaum, Mildred Buchsbaum, John Pearse and Vicki Pearse
Paper: 978-0-226-07874-8
Cloth: 978-0-226-07873-1
Electronic: 978-0-226-07627-0