Glossary of "Evolution (4th ed.)" by Futuyma & Kirkpatrick (2017)
- The condition of having two types of gametes of different sizes and forms, one large and immobile (the egg), the other small and usually mobile (the sperm).
- Futuyma, D. J. & Kirkpatrick, M. 2017. Evolution, 4th ed. -xviii + 602 pp. Sinauer Associates, Inc., Sunderland.