Answer:
A callus is a hardening of skin, keratin is the protein which is abundant in callus. Skin is a protective layer against a external environment. Outer layer of skin consist of keratin which is also found in hair. Callus is the accumulation of dead cells result due to friction and pressure exerts on the part in which they are present. The keratin component (keratinocytes) remains undifferentiated in these dead cells which causes hardening in callus.
Answer:
1 living organisms are composed of one or more cells.
2 The cell is the basic unit of structure and organization in organisms.
3 Cells arise from pre-existing cells.
Proteins are polymers, relatively large molecules made form many smaller molecules. Each protein molecules is built up from amino acids, smaller monomer molecules that join end to end to make the protein polymers molecule. <span />
A. Natural Selection. This is because the weeds that are not resistant to it die out before they can reproduce, but the resistant ones grow to maturity and then reproduce, passing down the resistance gene. Over time, the resistance gene would become a normal thing in weeds, while the non-resistant gene would not exist anyone, since the gene could not be passed on.
Answer:
B. Asexual reproduction involves one parent, and sexual reproduction involves two.
