While humans have chromosomal sex determination, some organisms exhibit environmental sex determination. Give an example of an organism where sex is determined by environmental factors and briefly explain how it works.

An example of an organism where sex is determined by environmental factors is the green sea turtle (and many other reptile species like crocodiles and alligators). In green sea turtles, the sex of the hatchlings is determined by the temperature at which the eggs are incubated during a critical period of embryonic development. This phenomenon is known as Temperature-Dependent Sex Determination (TSD). 

High Incubation Temperatures: Typically produce female offspring. 

Low Incubation Temperatures: Typically produce male offspring. 

Intermediate Temperatures: Can produce a mix of both sexes. This means that the same genetic makeup can lead to either a male or a female, depending on the external environmental conditions experienced by the embryo. 

This is a significant contrast to chromosomal sex determination where sex is fixed at fertilization.