Organ system is the answer
Genetic variation<span> occurs </span>mainly<span> through DNA mutation, gene flow (movement of genes from one population to another) and sexual reproduction</span>
Answer:
electrons
Explanation:
Electrical energy is caused by moving particles that have a negative or positive charge. These particles are called electrons
<h2>Urea </h2>
Explanation:
Urea is a small nitrogenous compound which is the main end product of protein catabolism in mammals
- Urea is a nitrogen-containing substance normally cleared from the blood by the kidney into the urine
- It is made predominantly in the liver from ammonia and bicarbonate and is one of the main components of urine
- The rate of synthesis varies from 300 to 600 mmol/day depending on the protein intake
- All of this urea eventually finds its way into the urine
- Because urea makes up a large part of the obligatory solute excretion, its osmotic pressure requires significant volumes of water to carry the urea
- Urea passively crosses biological membranes, but its permeability is low because of its low solubility in the lipid bilayer
- Some cells speed up this process through urea transporters, which move urea by facilitated diffusion
- Urea is passively reabsorbed in the proximal tubule, but its route of transport is not clear
- Urea transporters have not yet been identified for the proximal tubule
