What are the mechanisms or methods of sex determination in different organisms?

Different organisms use different mechanism of sex determination. In some species it is genetic and in a few cases, sex is determined by environmental factors, such as temperature. The temperature at which fertilized eggs are kept determines the sex of the organism developing inside it. In snails, sex is not determined genetically. Snails practice sex change. Adults start out as male, and then they become female. However, in human beings, birds and some reptiles, sex is determined genetically. The genetic constitution of the zygote formed after fertilization decides the sex of the offspring.