Which of the following is an example of how a scientist might use a model?

marbles placed inside a hollow sphere are used to describe protons in a nucleus.

microscopes are used to magnify a group of cells on sets of slides.

a wrench is used to tighten a nut onto a piece of wood.

stopwatches measure the amount of time it takes for runners to complete a mile

How was the climate when the ambulocetus was alive

Ausable water source is one that can be used by humans for drinking or agriculture. identify the water reservoirs as usable or unusable based on their current state. oceans rivers glaciers freshwater lakes groundwater

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.