Nitrogen fixing bacteria living in the roots of legumes to absorb sugars from them is an example of: A. Commensalism
B. Predation
C. Parasitism
D. Mutualism

Hemoglobin is the compound in red blood cells that carries oxygen to the body. the distribution of hemoglobin in women in g/dl of blood is approximately normally distributed with mean 14 and standard deviation 1. too little hemoglobin, and you're anemic. 2. too much, and (unless you live at high altitudes), you can have other problems.

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.