Natural barriers include the skin, mucous membranes, tears, earwax, mucus, and stomach acid. Also, the normal flow of urine washes out microorganisms that enter the urinary tract. The immune system uses white blood cells and antibodies to identify and eliminate organisms that get through the body's natural barriers.
Typically, a cell electric potential across the cell membrane varies between -40mV and -80mV. The electric potential in cells such as the neuron enable the cells to transduce the electric signal from stimuli across the nervous system. In other cells, the electric potential powers the running of molecular devices such as the flagella motor in sperm cells
Lichens are widely used as environmental indicators or bio-indicators. If air is very badly polluted with sulphur dioxide there may be no lichens present, just green algae may be found. Therefore the answer is the air quality is good because of no lichens present
Feature B is an End Moraine
