Hello
When populations have differences in rituals or behaviors. When populations are separated by rivers, mountains, r bodies of water.
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The controlled experiments are performed by the scientists, when they want to study the changes in the sample on changing a single variable. So, the correct answer is option (b).
In case, all variables are kept same, no changes would be observed in the experiment sample. A controlled experiment can be performed on living thing as well as non living. But, controlled experiment cannot be performed on the things which are influenced by a lot of variables, as they cannot create realistic results. So, the option (a), (c), and (d) are incorrect.
ANSWER:⇒ cork
People struggled to believe that some of Hooke's images were real because they were so strange and remarkable! Hooke noticed tiny boxlike spaces in cork under his microscope, which he depicted and characterized as cells. Plant cells have been discovered by him!