Final answer:
Filtration is the microbial control method that physically removes microbes from samples without killing them or inhibiting their growth. Experimental controls are essential for scientific studies to compare outcomes between different groups. ALCOA's control over bauxite exemplifies economic control over a physical resource.
Step-by-step explanation:
An example of a physical control that does not kill microbes or inhibit their growth but instead physically removes them from samples is filtration. This method is very effective in clearing samples of microbial presence without affecting the microorganisms themselves. Other control methods like desiccation and lyophilization are designed to either remove water from the microorganisms or freeze-dry them, which can inhibit their growth or kill them. Nonionizing radiation is also a microbial control method, but it works by altering the DNA of microbes and therefore has a different mechanism of action compared to filtration.
Experimental controls are crucial in research because they allow scientists to compare between test groups and control groups that differ only in the one variable being tested. For instance, in a study where an experimental group learns algebra using a computer program and a control group learns through traditional classroom teaching, it allows researchers to isolate the effects of using technology on learning outcomes.
Physical resources can also be controlled in a non-microbial context, such as ALCOA’s historical control over bauxite, which gave them a natural monopoly. This is a control over a physical resource that gives an entity economic power rather than control over biological entities.