1. which characteristic of potassium makes it useful for dating rocks?

it has a long half-life.
it decays at an unknown rate.
it produces lead as it breaks down.
it can be used to date all types of rock.

2. which statement describes the law of superposition?

sedimentary rocks were originally in horizontal layers.
in horizontal rock layers, each layer is younger than the one below it.
rock layers must be in existence before something can happen to them.
rocks that are not in horizontal layers were shifted by some geologic event.

Mouse liver cells were homogenized and the homogenate subjected to equilibrium density-gradient centrifugation with sucrose gradients. fractions obtained from these gradients were assayed for marker molecules (i. e., molecules that are limited to specific organelles). the results of these assays are shown in the figure. the marker molecules have the following functions: cytochrome oxidase is an enzyme involved in the process by which atp is formed in the complete aerobic degradation of glucose or fatty acids; ribosomal rna forms part of the protein-synthesizing ribosomes; catalase catalyzes decomposition of hydrogen peroxide; acid phosphatase hydrolysis monophosphoric esters at acid ph; cytidylyltransferase is involved in phospholipid biosynthesis; and amino acid permease aids in transport of amino acids across membranes. a) name the marker molecule and give the number of the fraction that is most enriched for each of the following cell components: lysosomes; peroxisomes; mitochondria; plasma membrane; rough endoplasmic reticulum; smooth endoplasmic reticulum.

Apaleontologist finds a plant fossil that shows that the plant had seeds. what can the paleontologist conclude?

Which member of the following food chain will be least affected by ddt, a pesticide water pollutant, if bio-magnification is occurring? algae> zooplankton> crayfish> leopard frog> large mouth bass