• The internal fertilization process occurs within the body of female whereas, in external fertilization, fusion of sperm and egg occurs externally of the female body.
• After the internal fertilization, egg will come out of the body having a thick shell whereas, in external fertilization, eggs are produced with thin tertiary membrane or without membrane.
• External fertilization needs water, whereas internal fertilization does not need water to fertilize.
• Organisms involved in external fertilization have mobile male gametes with flagella, whereas organisms involved in internal fertilization has immobile male gametes.
• In internal fertilization, wastage of gametes is lower, whereas wastage of gametes is higher in external fertilization.
• Organisms that involved in internal fertilization produce lower number of gametes, whereas organisms involved in external fertilization produce a large number of gametes.
• Survival of organisms that involved in internal fertilization is higher than the survival of organisms involved in external fertilization.