A mule is the result of a horse that has been bred with a donkey. Mules are generally sterile, meaning that they cannot be bred with each other in most cases. They also have 63 chromosomes. In appearance, mules may look very similar to donkeys. They also have stiff hair. Much like donkeys, mules are strong animals and tend to have calmer personalities.
Air Embolism. An air embolism is an obstruction in a vein or artery caused by a bubble of gas. Air enters the circulatory system when the pressure gradient favors movement of air or gas from the environment into the blood. A venous air embolism is the most common form of air embolism.
What causes air pollution? Air pollution can result from both human and natural actions. Natural events that pollute the air include forest fires, volcanic eruptions, wind erosion, pollen dispersal, evaporation of organic compounds and natural radioactivity. Pollution from natural occurrences is not very often. Human activities that result in air pollution include: 1. Emissions from industries and manufacturing activities. Consider a typical manufacturing plant: You will notice that there are long tubes (called chimneys) erected high into the air, with lots of smoke and fumes coming out of it.