A. <span>Exposure to an antigen
Exposure to viruses and antigens led to the foundation of modern vaccination. Vaccination introduces an antigenic material that helps the ability of the immune system to adapt a specific pathogen, therefore leading to a long-term immunity.</span>
Answer:
Organism D.
Explanation:
Amino acids are the monomers of proteins and are linked together by the peptide bond. The protein is obtained from the RNA molecules by the process known as translation.
The amino acid sequence of the proteins can also be used to study the evolutionary relationship between the organisms and the closeness of teh organisms with each other. In the question it is give that organisms A and D has least difference ( 1 amino acid sequence difference) and more related with each other.
Thus, the answer is organism D.
The phase in the cardiac cycle when the mitral valve is closed and the aortic valve is open is the systolic ejection phase (Option D). It is the second phase of the ventricular systole.
The cardiac cycle is a sequence of contraction and relaxation of the atria and ventricles to pump blood throughout the body.
This cycle (cardiac cycle) can be divided into two major periods: diastole and systole.
The diastole is when the heart relaxes and refills with blood, while the systole is when the heart contracts and pumps blood.
The systolic ejection phase is the second phase of the ventricular systole where blood is pumped from the ventricle.
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Answer:
Producers are the foundation of a food chain.
Explanation:
They provide energy for all of the consumers in an ecosystem.