How do surface barriers work to prevent infection?
What will be an ideal response?
Physical barriers like skin and mucus membranes block pathogens from entering underlying tissue. Chemical barriers may trap pathogens, as does mucus, or may destroy pathogens, as do lysozymes, stomach acids, and bile salts. Resident bacteria also are a barrier since they can out-compete pathogens.
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A plant systematist studies the physiological systems of plants
a. True b. False
Which of the following is a possible advantage for the environment of having farmers use plants that genetically produce Bt toxin?
A) Plants with genes for the toxin are eaten less often by insects, and therefore less insecticide is needed. B) Plants that produce Bt toxin must be grown from new seeds each season, and therefore fewer of them are planted. C) Bt toxin is advantageous to many species of invertebrates that grow in the same fields. D) Harvesting plants with these genes is less disturbing to the soil layers where they are planted. E) Plants with these genes must be sprayed with the organism, but need much less than other plants.
Members of which group have formed deposits of chalk, as seen in the white cliffs of Dover?
a. euglenoids b. choanoflagellates c. diplomonads d. foraminiferans e. actinopods
A researcher suspects that the food in an ecosystem has been contaminated with radioactive phosphates over a period of months. Which of the following substances could be examined for radioactive phosphate to test the hypothesis?
A) the amino acids within proteins produced by organisms living in the area B) the starch produced by plants in the area C) the DNA of the organisms in the area D) All of the above are true.