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.
<span>If the black horse is homozygous, what is its genotype?
BB
If the black horse is heterozygous, what is its genotype?
Bb
Hope this helps!
-Payshence xoxo</span>