<span>Cattle and sheep are exposed to lead and zinc when these poisons are in the grass/soil.
Cattle and sheep graze on the grass, and thus they intake these minerals, such as lead and zinc when they come in contact with grass or earth they may eat along with grass. Thus they are exposed to them via eating.
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If he studied a small sample it wouldn't be a representative sample. since he got such a large sample there is a chance most likely all organisms follow the rules of evolution.
Regarding the order rhizobiales of the class Alphaproteobacteria, the genus that includes human pathogens is Brucella.
Rhizobiales are a type of Alphaproteobacteria, which are a type of Proteobacteria, which are Gram-negative bacteria.
Brucella is also a type of Gram-negative bacteria that can cause brucellosis, which is an infectious disease caused by eating unpasteurized milk or undercooked meat.
