How is sex determined in various organisms? Give the historical background of sex determination.

(N/A) The mechanism of sex determination has always been a puzzle for geneticists.
The initial clue regarding the genetic/chromosomal mechanism of sex determination can be traced back to experiments conducted on insects.
Cytological observations in several insects led to the development of the concept of the genetic/chromosomal basis of sex determination.
Henking $(1891)$ traced a specific nuclear structure throughout spermatogenesis in a few insects and observed that $50\%$ of the sperm received this structure,while the other $50\%$ did not.
Henking named this structure the $X$-body but could not explain its significance.
Further investigations by other scientists concluded that the $X$-body was actually a chromosome,hence it was named the $X$-chromosome.
It was observed that in many insects,the mechanism is of the $XO$ type,where all eggs bear an additional $X$-chromosome along with autosomes.
Some sperm bear the $X$-chromosome,while others do not.
Eggs fertilized by sperm with an $X$-chromosome become female,and those fertilized by sperm without an $X$-chromosome become male.
Due to the involvement of the $X$-chromosome in sex determination,it was designated as a sex chromosome,and the rest were named autosomes.
Grasshoppers are an example of $XO$ type sex determination,where males have only one $X$-chromosome besides autosomes,while females have a pair of $X$-chromosomes.
In many other insects and mammals,including humans,$XY$ type sex determination is seen,where both sexes have the same number of chromosomes.
Males have an $X$-chromosome,but its counterpart is distinctly smaller and called the $Y$-chromosome.
Females have a pair of $X$-chromosomes.
Thus,both males and females bear the same number of autosomes. Males have autosomes plus $XY$,while females have autosomes plus $XX$.