Sir Isaac Newton, held the theory that light<span> was </span>made<span> up of tiny particles. In 1678, </span>Dutch<span> physicist, </span>Christiaan Huygens<span>, believed that </span>light<span> was </span>made<span> up of waves vibrating up and down perpendicular to the direction of the </span>light<span> travels, and therefore formulated a way of visualizing wave propagation.</span>
        
                    
             
        
        
        
Answer:
Explanation: It is a region of the earth that is extremely biological diverse and also 
Under many threat due to habitat loss , clamate change or extensive species for guarding these region is important because host animals are there which is not found anywhere on earth 
 
        
             
        
        
        
The most powerful approach to isolating a single mutant from a population of billions is positive selection.
 
        
                    
             
        
        
        
A constant factor could be the dose of the drugs  and the species of the rats used.
<h3>What is a constant factor?</h3>
In an experiment, a constant factor is one that is not allowed to change al through the experiment. This one must be held as the same and not allowed to vary. A constant factor could be the dose of the drugs  and the species of the rats used.
The factor that would be different for the experimental group and the control group  the administration of the new drug.
Learn more about experiment:brainly.com/question/11256472
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