Environmental-Dependent Sex Determination in Reptilians
When we think of sex determination in organisms, we most often think of mitosis and the process of randomly receiving X and Y chromosomes from parent cells. This type of sex determination is known as genotypic sex determination (GSD), and it’s the most commonly found method of sex determination. However, this isn’t the only type of sex determination available to organisms. Some reptilians, for example, use environmental-dependent sex determination to determine the sex of newborns! At first, it may not make sense how environmental-dependent sex determination (ESD) can successfully work – after all, sex is determined by X and Y chromosomes and the process of mitosis that randomly determines …show more content…
For instance, temperature changes (such as those caused by the heating and cooling of the Earth) will select for the gender that relates to those temperatures. So, if the Earth were to suddenly cool down, then the gender that is associated with the cold (male, for example) would be selected for and the opposite gender would be selected against. This natural selection would occur during embryonic development instead of later in life. However, changes in temperature are not just limited to selection of gender – they can also influence the selection of traits. Although this isn’t as well known, and it’s still being researched, some studies have shown that some traits will be common in individuals raised in the same temperature. This raises the possibility that some other chemicals are also being affected by the temperature. If you think about it, this is very unique to TSD organisms. In organisms utilizing GSD, natural selection for or against traits occur immediately after birth and usually results in the death of an individual (and, if death does not occur, that individual may not be able to reproduce, which is very bad in evolutionary terms). However, in ESD organisms, selection of some traits can occur before the organisms is even fully developed! Furthermore, the natural selection of these temperature-dependent traits will not normally result in the death of the embryo. In fact, you could even say that this looks more like natural repression than natural
When we think of sex determination in organisms, we most often think of mitosis and the process of randomly receiving X and Y chromosomes from parent cells. This type of sex determination is known as genotypic sex determination (GSD), and it’s the most commonly found method of sex determination. However, this isn’t the only type of sex determination available to organisms. Some reptilians, for example, use environmental-dependent sex determination to determine the sex of newborns! At first, it may not make sense how environmental-dependent sex determination (ESD) can successfully work – after all, sex is determined by X and Y chromosomes and the process of mitosis that randomly determines …show more content…
For instance, temperature changes (such as those caused by the heating and cooling of the Earth) will select for the gender that relates to those temperatures. So, if the Earth were to suddenly cool down, then the gender that is associated with the cold (male, for example) would be selected for and the opposite gender would be selected against. This natural selection would occur during embryonic development instead of later in life. However, changes in temperature are not just limited to selection of gender – they can also influence the selection of traits. Although this isn’t as well known, and it’s still being researched, some studies have shown that some traits will be common in individuals raised in the same temperature. This raises the possibility that some other chemicals are also being affected by the temperature. If you think about it, this is very unique to TSD organisms. In organisms utilizing GSD, natural selection for or against traits occur immediately after birth and usually results in the death of an individual (and, if death does not occur, that individual may not be able to reproduce, which is very bad in evolutionary terms). However, in ESD organisms, selection of some traits can occur before the organisms is even fully developed! Furthermore, the natural selection of these temperature-dependent traits will not normally result in the death of the embryo. In fact, you could even say that this looks more like natural repression than natural