Online Resources: Level 2 Biology Learning Workbook (2021 edition and prior)

Level 2 Biology Learning Workbook, ISBN: 9780947504908 (2021 Edition)

Pages 37, 51, 52 and 62: Internal transport and gas exchange

Level 2 Biology Learning Workbook, ISBN: 9781877459078 (2012 Edition)

Page 10: Unicellular organisms the protista