To prevent blood flowing back after each heartbeat. They ensure that the blood flows only in one direction (back to the heart).
Answer:
Polarity is the distribution of electric charge over the atoms joined by the bond.
Answer:Changes that affect the structure of chromosomes can cause problems with growth, development, and function of the body's systems. These changes can affect many genes along the chromosome and disrupt the proteins made from those genes.
Structural changes can occur during the formation of egg or sperm cells, in early fetal development, or in any cell after birth. Pieces of DNA can be rearranged within one chromosome or transferred between two or more chromosomes. The effects of structural changes depend on their size and location, whether gene function is interrupted, and whether any genetic material is gained or lost. Some changes cause health problems, while others may have no effect on a person's health.
Explanation: took the test
The west Nile Virus is pathogen which caused the West Nile fever and encephalitis. The pathogen was introduced in 1999 in the Western Hemisphere and infected a major population in new york. It then expanded to 12 states and district of columbia. The major carrier of the pathogen was Avian and Mosquitoes species. In between 1999 to 2008, nearly 2500000 people were infected and nearly 1500 people died. Also there were thousands of cases of encephalitis or meningitis.
They both can be traced back millions of years ago
