From simplest to most complex the four levels of organization of the human body are
a. tissues, cells, organs and organ systems.
b. cells, tissues, organs and organ systems.
c. organ systems, tissues, cells and organs.
d. cells, organs, tissues and organ systems.

Enzyme speed up chemical reaction are which type of marcomolecule? a.carbohhydrates b.protiens c.lipids d.nucleic acids

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.

Food webs - transferring energy and matter from one level to another. here you see four food webs. one or more are incorrect. which food web(s) show the correct sequence of organisms, from start to top level consumer? a) a b) d c) c d) a and d