The double helix is a description of the molecular shape of a double-stranded DNA molecule. In 1953, Francis Crick and James Watson first described the molecular structure of DNA, which they called a "double helix," in the journal Nature.
Worldwide, there are 107 boy babies born for every 100 girl babies. This skewed ratio is partly due to sex-selective abortion and "gendercide," the killing of female infants, in countries such as China and India where males are more desired. But even discounting those factors, the completely natural male-to-female sex ratio still hovers around 105:100, meaning that women are inherently more likely to give birth to boys. Why?
Several factors influence whether a sperm containing a Y sex chromosome or one containing an X chromosome will be first to fertilize an egg, including parental ages, their environmental exposure, stress, the stage in the mother's ovulation cycle and even whether she has had children previously; all these forces combine to set the average sex ratio at fertilization at 105:100.
C. A slow gradual change over time
Algal blooms can result in creating low oxygen zones, referred to as the dead zones in aquatic ecosystems. This happens because the algae overall consume more oxygen than they produce and when they die even more oxygen is removed from the ecosystem in the process of their decomposition. This leaves the ecosystem depleted of oxygen and aggravate the living conditions in the ecosystems,