<u>Answer and Explanation</u>:
In reptiles, there are two mechanisms of sex determination:
-Genetic mechanisms, determined at the fertilization moment
-Environmental mechanisms, which are temperature-dependent.
Temperature is an environmental factor that affects different processes in organisms at a molecular level, biochemical level, or physiological level. In reptiles such as lizards, snakes, turtles, crocodiles, among other, temperature influences their embryonary development, their growth, daily activities, reproduction rate, sex determination, and etc.
In lizards, it occurs that whenever eggs are incubated at low temperatures, between 22 º and 27ºC, they produce a higher percentage of males, while eggs exposed to higher temperatures, 30ºC and above, produce more females. There are only a few degrees of temperature at which exposed eggs produce males and females equally.
The importance of knowing the mechanism of organisms´ sex determination lies in how climate change may be affecting wild populations due to fluctuations in temperature.
In the exposed example, the first cross between ZZ males and ZW females, genetics is the mechanism that determines the sex of progeny produced from eggs incubated at 24 and 35 degrees celsius. While in the second cross between ZZmales and ZZ females, temperature determines the sex of progeny produced from eggs incubated at 24 and 35 degrees celsius. This is, eggs exposed to temperatures below 28ºC will produce only males, so there won't be any female in the progeny. But eggs incubated at 30ºC and over will produce females, as shown in the table.
