Which of the following statements are part of Koch’s Postulates? Check all that apply. A - The disease-causing microorganism must be present in at least half of the cases of disease.

B -The microorganism can be isolated and grown in a pure culture.

C - The microorganism from the pure culture will cause the disease in at least 80% of healthy organisms.

D - A re-isolated microorganism may evolve into a different species than the original.

Are substances released into the environment that in excess amounts cause damage

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Aresearcher has developed two stains for use with seed plants. one stains sporophyte tissue blue; the other stains gametophyte tissue red. if the researcher exposes pollen grains to both stains, and then rinses away the excess stain, what should occur? a) the pollen grains will be pure red.b) the pollen grains will be pure blue.c) the pollen grains will have red interiors and blue exteriors.d) the pollen grains will have blue interiors and red exteriors.