You are experimenting with cell division on the root cells in an allium cepa plant in your lab. before they can divide the dna must be copied, but the cells seem to only be copying part of the dna and stopping. which material might the cell not have enough of to replicate its dna?
a. uracil
b. ribosomes
c. cytosine
d. triglycerides

Why is excretion necessary to maintain homeostasis?

Which of the following is the best definition of aerobic respiration? o a. the cellular process that releases energy by breaking down glucose o b. physical activity that involves the repeated motion of large muscle groups o c. physical activity that increases heart rate and breathing rate o d. the cellular process that converts solar energy to chemical energy

Some birds look for food near cattle and other livestock. the movement of the cattle churns up the ground, making insects available to the birds. the cattle appear to be unaffected by the presence of the birds. what kind of relationship exists between the birds and the cattle? o a. parasitism o b. commensalism o c. predation o d. mutualism