If you test more than one variable in an experiment at a time than you wouldn't know what variable caused the change in the end.
Answer:
The immune system responds to antigens by producing cells that directly attack the pathogen, or by producing special proteins called antibodies.
Explanation:
Specific immune responses are triggered by antigens. Antigens are usually found on the surface of pathogens and are unique to that particular pathogen. The immune system responds to antigens by producing cells that directly attack the pathogen, or by producing special proteins called antibodies.
The immune system review (article) | Khan Academy
Acquired immunity is the type of immunity that exists when a person is exposed to an antigen and subsequently makes antibodies against the antigen.
Immunity is the defense mechanism of the nervous system to avoid pathogens affecting the body and making it sick. There are two major types of immunity: innate and acquired. Innate immunity is the kind of immunity present in the human body by birth. Whereas, acquired immunity is gained over time.
Acquired immunity specifically promotes the antibodies or lymphocytes to inhibit the action of pathogens when it encounters one. It is further categorized into two types: active and passive immunity.
Active immunity indulges in the primary response to a pathogen. It produces antibodies to fight against it and preserves some to fight against the same pathogen encountered for the second time. Passive immunity, in addition, involves the medications prescribed to enhance immunity.
To know more about acquired immunity, refer to the following link:
brainly.com/question/26864713
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Answer:
Natural selection is the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable, meaning that they are all different in some ways. ... Individuals with adaptive traits—traits that give them some advantage—are more likely to survive and reproduce.
