Question

Why would paired external fertilization be preferable to group spawning?

Short answer

Paired external fertilization allows the female to select the male for mating. It also has a greater chance of fertilization taking place.

Step-by-step solution

Step 1. Introduction

External fertilization is a mode of reproduction in which a male organism's sperm fertilizes a female organism's egg outside of the female's body.

Step 2. Explanation

Paired external fertilization be preferable to group spawning because paired external fertilization allows the female to select the male for mating. It also has a greater chance of fertilization taking place, whereas spawning just puts a large number of sperm and eggs together and random interactions result in the fertilization.