Answer:
Nucleotides are the subunits of DNA. The four nucleotides are adenine, cytosine, guanine and thymine. Each of the four bases has three components, a phosphate group, a deoxyribose sugar and a nitrogen-containing base.
Answer: B
Explanation:
Ammonia is so toxic that it can be transported and excreted only in large volumes of very dilute solution. As a result most terrestrial animals simply don't have access to sufficient water to routine excrete ammonia.
The main advantage of urea is its very low toxicity. Animals can transport urea in the circulatory system and store it safely in high concentrations. Also much less water is loss when a given quantity of nitrogen is excreted in a concentrated solution of urea than would be in a dilute solution of ammonia.
Evolution is the gradual process resulting in the changes in the genetic material of a population over generations. The mechanism that Darwin proposed for evolution is the process of natural selection. Natural selection is the key mechanism of evolution which increases the frequency of advantageous alleles in a population. Due to the limited resources in nature, organism with heritable traits favoring their survival and reproduction produce more offspring. It causes the population to become adapted to their environment and results in organisms with better survival ability and reproduction. These traits become heritable due to the reproductive advantage and are passed from the parents to the offspring. Over generations, the advantageous heritable trait becomes dominant in the population. It is responsible for the variation in the gene pool of the population which increases their fitness.
Its is to remove liquid waste from the blood in the form of urine, and keep a stable balance of salts and other substances in the blood and produce erythropoietin, hormone that is the formation of ref blood cells. The kidney remove ursa from the blood through this filtering units called nephrons
