Photoreceptors are distributed over the entire neural retina, except where the optic nerve leaves the eyeball. This site is called the .
optic disc
macula
lutea

Natalie had random hand movements when she was two months old. when she was six months old, she used to grab a block with her whole hand. now at the age of ten months, she can grasp the same block with her thumb and forefinger. this sequence of growth in her hand and finger movements is according to the pattern.

Number and variety of living organisms includes genetic, species, and ecological types

Nucleic acids offer variability because they contain alternate forms of genes called .