Are sand dunes constructive and destructive

Why is it important to reduce the number of chromosomes in half when forming gametes for sexual reproduction?

What is the function of the somatic nervous system? connects the brain and the spinal cord to the rest of the body carry signals to the muscles and glands includes all nerves controlling the muscular system and external sensory receptors controls internal organs like the heart and bladder

Individuals do not compete directly for resources, but are prey for the same predator