Metabolism is
1. a measure of the hydrogen ion concentration in a solution
2. the energy required to start a chemical reaction
3. all of the chemical reactions in an organism required to sustain life
4. a chemical reaction in which the substrates trade constituent parts

2. if scientists identify an animal with bilateral symmetry and no segmentation, which phylum can it definitely not belong to? a. roundworms b. annelids c. mollusks d. flatworms

How is ribosomal rna useful as a molecular clock? a. a large portion of the dna ring is not vital to structure or function, allowing it to accumulate neutral mutations. b. its rate of mutation increases over time as organisms continue to evolve and differentiate from each other. c. a slow mutation rate makes it useful for determining evolutionary relationships between ancient species. d. it is only found in select organisms, making it easier to compare relationships between species that have it.

Light sensitivity in euglena is provided by the