Zoology, animal biology, ethology studies the Australian central bearded dragon.
The sex of the central bearded dragon hatchlings is determined by the prevailing temperature during incubation. Some females carry male genes and behave like males. They are more confident and active than other females. The "tomboys" also have more offspring.
Of great interest is how genetic and climatic factors affect gender. In lab test incubation, if the temperature was over 32 degrees females with male chromosomes hatched as females. Below 32 degrees the dragon expressed its genetic disposition and hatched as males. High temperature females were larger than males which is normal for the species.
It appears that male type behaviors of these females is genetically determined. Some of the females were even bolder than normal males. Male chromosomes affect the brain which is driven to express male traits. Only one other animal has the feature of environmental and genetic factors determining sex - the skink.
Other animals use either temperature or genes for gender disposition. It is possible that they did have both mechanisms early in evolution. but one was lost. If the climate changes and becomes warmer animals who only use temperature would produce only males and could become extinct. The two remaining animals who use both features would survive whether the climate changed or remained the same.
◆ Zoology by Ty Buchanan ◆
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