Answer:
Hair and nails are mostly made of protein. Your body uses protein to build and repair tissues. You also use protein to make enzymes, hormones, and other body chemicals. Protein is an important building block of bones, muscles, cartilage, skin, and blood.
Explanation:
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in heritable traits of a population over time. The term "natural selection" was popularised by Charles Darwin who compared it with artificial selection, now more commonly referred to as selective breeding.
A theory which is tested again and again and found to fit the facts and from the valid predictions may be made is then known as scientif ic law or priciples..
A) single loop
Fish have a two-chambered heart in which a single-loop circulatory pattern takes blood from the heart to the gills and then to the body.
