How do species determine sex?
From humans to animals, there are countless species in nature that have both sexes. But what determines the sex of a species? Is it genetics, the environment, or a combination of both? In fact, there are great differences in how different species determine sex, with some species having only one sex and others potentially having three or more sexes. If you want to learn more about the secrets of sex determination and the mysteries of these mechanisms, read on.
What are the ways sex is determined in the animal world?
Chromosomal sex determination is the most common modality. In most animals, the sex of males and females is determined by chromosomes. A typical example is that in humans and other mammals, males have XY chromosomes, while females have XX chromosomes. Sex-determining genes at specific loci are key to determining sex. In males, sex-determining genes lead to the development of reproductive organs, while in females they play the opposite role.
Environmental sex determination is also a common form of sex determination. In some animals, specific environmental conditions affect an individual's sex. For example, the sex of some reptiles, such as crocodiles and turtles, is affected by the temperature at which they hatch. Incubation areas with high temperatures lead to the appearance of females, while areas with low temperatures produce males. This way of determining gender has a certain degree of flexibility and is subject to environmental influences.
There are also animals that use intersex sex determination. This means that an individual can have both female and male traits throughout his or her lifetime. For example, some fish and invertebrates are hermaphroditic. In this case, the individual can self-fertilize or reproduce with other individuals.
There are also special ways of sex determination that exist in the animal world. In lizards, for example, a gene called "determining-gene" can determine an individual's sex. This gene can be expressed during an individual's development, which in turn determines whether the individual is male or female. In birds, for some species, sex is determined by sex-determining genes for specific chromosomes in eggs.
Which species have sex determined by environmental factors?
Crocodile The crocodile is one of the species that determines sex by temperature. During incubation, temperature affects sex chromosome expression in crocodile embryos. Low temperatures lead to the appearance of more male crocodiles, while high temperatures tend to produce more female crocodiles. This phenomenon is known as temperature sex determination.
Scientists have come up with a possible explanation called the "gender regression theory." According to this theory, female crocodiles can only survive in warm environments. In such an environment, female crocodiles can better provide the stable conditions needed to hatch and care for their young. Conversely, male crocodiles are more adapted to cold environments because lower temperatures allow them to gain more energy to increase the success rate of reproduction.
Some turtle species are also affected by temperature and determine their sex. In many turtle species, low temperatures produce male larvae and high temperatures produce female larvae within a specific temperature range. This is known as temperature sex determination.
The study found that there are physiological reasons behind the sex determination of temperature differences. At low temperatures, the sexual differentiation of turtle larvae is inhibited, resulting in the emergence of more male individuals. At high temperatures, sexual differentiation accelerates, and females become the dominant sex.
In the wild environment, temperature sex also plays an evolutionary advantage. For example, male turtles are more likely to find partners in cold environments, increasing reproductive success. Female turtles, on the other hand, are more likely to find suitable nests to lay eggs in hot environments.
Lizards Lizards are also one of the temperature-regulated sex-determined species. Similar to crocodiles and turtles, sex determination in lizards also depends on the temperature at which they are exposed during the embryo.
For some lizard species, high temperatures lead to more male individuals, while low temperatures tend to produce more female individuals. Temperature determines sex by affecting specific areas of chromosomes.
What are the evolutionary and future trends of gender determination?
In the early biological world, there was a primitive sex determination method, that is, the chromosomal sex determination method. In this way, an individual's sex is not determined by chromosomes, but by other mechanisms. For example, for some invertebrate and plant species, sex can be determined by environmental factors, body chemicals, or other physiological processes.
Evolution of chromosomal sex determination As organisms evolve, chromosomal sex determination patterns gradually form in species. This way means that an individual's sex is determined by chromosomes, usually by the type of sex chromosome. In humans and other mammals, males have XY chromosomes, while females have XX chromosomes. This way of sex determination has gradually become dominant in the process of evolution.
In some species, sex determination is determined by specific sex chromosomes (not necessarily XY or XX) or other sex determinants. For example, the way sex is determined in birds is determined by the ZW chromosome, where females have ZW chromosomes and males have ZZ chromosomes.
In addition to chromosomes determining sex, there are some species whose sex determination is influenced by environmental factors. For example, the sex determination of some species in reptiles is determined by temperature, with individuals hatching at high temperatures tending to be females and individuals hatching at low temperatures being males. This mechanism of environmental sex determination can provide some advantages for adaptation to environmental changes.
Future trends and prospects With the continuous development of science and technology, human research on the way of sex determination is also deepening. Future trends may be more analytical mechanisms of action for sex chromosomes and other determinants of sex. At the same time, the development of gene editing technology may also affect the way species determine sex. This may lead to people being able to choose the sex of the baby, but also face ethical and social issues. Therefore, in future trends, scientists and policymakers need to weigh the balance between ethics and scientific and technological progress.
