Answer: Antigens
Explanation: The ABO system of blood grouping is based on the basis of the type of antigens that are present in the red blood cells. Erythrocytes is another name for the red blood cells. Antigens are molecules that are capable of eliciting immune response. There are two types of antigens: antigen A and B. Blood type A has only antigen A, blood type B has only antigen B, blood type AB has both antigen A and B while blood type O has no antigen (neither A nor B antigen).
Similarly, Rh trait is determined by the presence or absence of rhesus antigen in the erythrocytes. Rhesus antigen is an antigen first discovered in rhesus monkey. Rh+ indicates the presence of rhesus antigen in the red blood cells while Rh- indicates the absence of rhesus antigen in the red blood cells.
The biologist is the person who would be interested in determining the existence of any pattern or characteristics with in a species and relate it to the characteristics possessed earlier by the species.
Answer:
C. the medulla oblongata, which is in contact with cerebrospinal fluid, monitors pH and uses this measure to control breathing.
Explanation:
The central chemoreceptors are located near the medulla inside the blood-brain barrier. When CO2 in cerebrospinal fluid increases, pH of the fluid lower (because CO2 becomes hydrated to carbonic acid). Change in pH stimulates the central chemoreceptors to activate respiratory centers which will increase the respiratory rate and depth of breathing.
