Answer:
Shape of Red Blood Cells Erythrocytes are biconcave discs with very shallow centers. This shape optimizes the ratio of surface area to volume, facilitating gas exchange. It also enables them to fold up as they move through narrow blood vessels.
Explanation:
Melanin is the pigment which absorbs UV light and it is present in skin and gives black colour to it.As we can see africans usually have black skin as they have to face direct uv light.
Muscle contraction that results in a change in joint angle is called <span>concentric contraction.
This contraction occurs when enough force that can overcome the resistance applied is developed by the muscle where this force developed is larger than the force of the resistance applied.</span>
Answer:
Petiole
Explanation:
The petiole is the part of the leaf that attaches the leaf to the main stem of the plant. Depending on the leaf structure of the plant, some leaves may be devoid of a petiole, and be regarded as apetiolate.
