Which macromolecule forms a double layer as the primary structure of cell membranes?

Competition occurs between species when

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

Which best describes a gene? a. a sister chromatid b. a chromosome c. a tetrad d. a piece of a chromosome