What portion of the cell membrane is responsible for preventing unwanted materials from entering the cell?

Witch type of microscope is used to view very small cell components like proteins and dna?

Molecular models of two different substances are shown below. in the molecule on the left, the oxygen atom pulls on electrons more strongly than the hydrogen atoms. in the molecule on the right, the two oxygen atoms pull on the shared electrons with the same strength. water molecule, h, o oxygen molecule, oz when the two substances are put in the same container, they do not attract each other. why does this happen? a. they both contain oxygen. b. one is polar and one is nonpolar. c . they are both polar. d. they contain different elements.

Compare and contrast cladistics and phylogeny. what are their advantages and disadvantages? which is the most useful in understanding how an organism developed into its current form? which concept most strongly supports your opinion about the origin of any given organism?