Answer:
Mechanical barriers — which include the skin , mucous membranes , and fluids such as tears and urine — physically block pathogens from entering the body. Chemical barriers — such as enzymes in sweat , saliva , and semen — kill pathogens on body surfaces.
Answer:
Anatomy. Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
Molecular biology. DNA and the genetic code reflect the shared ancestry of life ...
Biogeography ...
Fossils ...
Direct observation
Explanation: