Author: green grass
Link:/question/26249279/answer/32695198
Source: Zhihu.
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This question, perhaps the following article, which claims to have won the "holy grail" of evolutionary biology, can answer your doubts ~
At present, there are many hypothetical theories (nonsense), and there are not many reliable experiments, which are largely limited to the long life cycle of crocodiles and turtles (I can't afford to run wild, can I talk nonsense about the miserable life of biological farmers, not to mention the long life cycle of these guys ~)
The famous theory is Charnov-Bull model, which holds that temperature-dependent sex determination (TSD) can maximize the fitness of population. However, this theory has not been proved by anyone, and it is even called the "holy grail" in evolutionary biology.
In 2008, D. A. Warner and R. Shine published their research on lizard Jackie Dragon in Nature.
& ltimg src = "/4 f 46 b 7 e 5826 13 1d 1 53876 c 7 a2 D5 aece 9 _ b . jpg " data-raw width = " 550 " data-raw height = " 368 " class = " origin _ image zh-light box-thumb " width = " 550 " d A TA-original = "/4 f 46 b 7 e 5826 13 1d 66
Foreigners seem to have no concept of "dragon".
Specifically, it is known that lizards can develop into females at 23~26 degrees and 30~33 degrees, and the temperature between them develops into males. In addition, the temperature regulation mechanism of lizards is regulated by non-aldosterone aromatase, and the sex differentiation of lizards can be accurately controlled by using the inhibitor of this enzyme.
Since the life cycle of this lizard is generally only four years (short-lived), they can calculate the fitness of a life cycle. Different induction strategies were designed in the experiment, and inhibitors were used to eliminate the influence of temperature. It is found that their results are very consistent with Charnov-Bull model. Experiments show that TSD strategy has different effects on the reproductive success rate of males and females, and can make the population reach the maximum fitness.
Of course, this is raised in the laboratory, not a crocodile (poor students can't afford it ~)
-Add the results, although few people pay attention (depressed ~ ~ whoops ~ ~)
Above, this is the fitting diagram that Jackie Chan got by fitting with Charnov-Bull model in the aforementioned Nature diagram 1.
& ltimg src = "/45 1 ac 2533507d 804d 6 f 77 e 57 e 3c 764 da _ b . jpg " data-raw width = " 600 " data-raw height = " 604 " class = " origin _ image zh-light box-thumb " w idth = " 600 " data-original = "/45 1ac 2533507d 804d 6 f 77 e 57 e 3c 764 da _ r。 Simply put, the abscissa is the different induced temperatures of eggs, the ordinate is the fitness, the black line represents the fitness of offspring males, and the dotted line represents the fitness of females. Figure A shows that offspring can get the highest fitness according to natural adjustment (the temperature on both sides produces females and the temperature in the middle produces males). Figure b shows the fitness of offspring if the sex determination of females is not regulated by temperature, while that of males is regulated by temperature; Fig. c sex determination of male is not regulated by temperature, while that of female is regulated by temperature, which leads to the fitness of offspring; Figure D shows that females and males have the same response to temperature regulation. Simply put, the abscissa is the different induced temperatures of eggs, the ordinate is the fitness, the black line represents the fitness of offspring males, and the dotted line represents the fitness of females. Figure A shows that offspring can get the highest fitness according to natural adjustment (the temperature on both sides produces females and the temperature in the middle produces males). Figure b shows the fitness of offspring if the sex determination of females is not regulated by temperature, while that of males is regulated by temperature; Fig. c sex determination of male is not regulated by temperature, while that of female is regulated by temperature, which leads to the fitness of offspring; Figure D shows that females and males have the same response to temperature regulation.
Next, they did experiments for several years. ...
Look at this photo:
& ltimg src = "/c 372 AE 07 e 4796 ca 1 2c 028 db 5 c 39 EC 965 _ b . jpg " data-raw width = " 800 " data-raw height = " 967 " class = " origin _ image zh-light box-thumb " width = " 800 " da ta-original = "/c 372 AE 07 e 4796 ca 12c 028 db 5 c 39 EC 965 _ r . jpg " >； This picture was made by them from June 2005 to July 2007, and the statistics of the data have been carried out for three years. The chart and A in the above picture are very similar to mine, so I won't go into details. The results are almost perfectly matched with the data fitted by the model, which proves that different temperature determination strategies can maximize the fitness of future generations. The establishment and verification of this model is also very interesting. Let's add it when we have a chance ~ This picture is the data statistics they made from 05-06 to 06-07. The chart and A in the above picture are very similar to mine, so I won't go into details. The results are almost perfectly matched with the data fitted by the model, which proves that different temperature determination strategies can maximize the fitness of future generations. The establishment and verification of this model is also very interesting. Come back and add it when you have a chance ~
Ps: I'm not in the related field. Please correct me if you have any questions in the discussion ~ Meng Mengda ~
Reference: When is gender determined by the environment?
Heredity-Abstract: Changes in the Mechanism of Heterogamy Determined by Sex
/nature/journal/v 45 1/n 7 178/full/nature 065 19 . html
ics .
The specific change mechanism mainly includes the following aspects:
1. Methylation and acetylation modification at chromatin level and DNA molecular level.
The expression of DNA is mainly regulated by the regulatory sequence in the upstream cis-acting element and the methylation modification degree of the downstream sequence. The methylation of DNA molecules is generally affected by the environment.
2.RNA interference
Some small double-stranded RNA(dsRNA) can silence the mRNA of its complementary sequence. These dsRNA can be exogenous or endogenous.
3. Emergency response in extreme environment
For example, HSF heat stress factor induces the expression of HSP heat stress protein, which helps the newborn peptide to fold correctly at high temperature.
For example, the coat color of female Sanhua cat is caused by the random inactivation of one of the X chromosomes. It is called dose compensation effect, and the highly concentrated inactivated X chromosome is called Pasteur's corpuscle, and the inactivation process is called Leonization.
X chromosome carries cat coat color gene, B is black coat color and B is orange coat color. In the process of growth and development, one X chromosome in somatic cells is randomly inactivated, so the coat color alternates between black and orange.