What is the mechanism of sex determination in some reptiles?
Temperature-dependent sex determination
Hormone-dependent sex determination
Presence or absence of the Y chromosome
Combination of sex chromosomes
Explanation: The temperature at which the eggs are incubated during a crucial time of development determines the sex of the progeny in various reptiles, including turtles, crocodiles, and some lizards. The phrase "temperature-dependent sex determination" (TSD) applies to this.
For instance, only male offspring are produced when incubation temperatures fall below a particular threshold while only female offspring are produced when incubation temperatures rise above the threshold. Both male and female offspring can be produced at intermediate temperatures. Each species may have a different temperature threshold and range.
As opposed to mammals and birds, TSD is not affected by the presence or absence of sex chromosomes. It is believed to have originated as an ancestral characteristic instead, prior to the development of sex chromosomes. The regulation of genes involved in sex determination and differentiation is believed to be the exact process by which temperature affects sex determination, albeit this is not entirely understood.
Option 1 is the correct answer.