Question

What determines which sex will result in offspring of birds and mammals?

Short answer

In mammals, sperm from the male determines the sex of the offspring. In birds, however, it is the female's sex chromosome that determines offspring sex.

Step-by-step solution

Step 1. Introduction

A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes.

Step 2. Explanation

• The presence of the W chromosome in birds determines femaleness
• The presence of the Y chromosome in mammals determines maleness.
• The absence of those chromosomes and the homogeneity of the offspring (ZZ or XX) leads to the development of the other sex.