-Yes it is possible that a structure as complex as an image-forming eye evolved by natural selection. if the photoreceptor cells and simple eyes that preceded it were useful to the animals in which they arose. Additionally, such photoreceptors and simple eyes can be seen in many living animals.
-According to scientists; the simple light-sensitive spot on the skin of some ancestors gave it some tiny survival advantage. Random changes then created a depression in the light-sensitive patch, a deepening pit that made "vision" a little sharper and also the pit's opening gradually narrowed, so light entered through a small aperture. Then the light-sensitive spot evolved into a retina, the layer of cells and pigment at the back of the human eye and over time a lens formed at the front of the eye.
<span> limiting factor </span> <span>A limiting factor is anything that is in short supply in the environment and therefore limits life processes</span>
That is why cells in normal conditions do not continue to divide uncontrollably like cancer cells. One of the reasons cancer cells continue to divide is their loss of cell cycle control. They can't be put into a G0 phase to wait until the enviornment is favorable for cell division.
