Why are the guard cells so important in a leaf?

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.

As a small change in a person's dna can cause a genetic disorder

Mineral rich water heated by newly found oceanic crust escapes through cracks in the ocean floor called