The circulatory system is similar to a road & highway system because the circulatory system is a way for nutrients and other stuff to flow through to your muscles, brain and organs (The nutrients and stuff are like cars). The blood veins, and vessels are like the roads that direct the stuff to the places they need to be.
Answer:
Phylogenetic trees can be described as diagrams which represents the evolutionary histories of organisms. The organisms that share more common traits or functions are more closer to one another in the diagram.
The phylogenetic tree in the above diagram shows that the ancestors of Danes, Chinese and Tibetans carried the regular EPAS1 alleles.
According to the tree, the Chinese are more closer to the Tibetans as they carry the Tibetan EPAS1 alleles which the Danes do not carry.
Answer: An independent variable is exactly what it sounds like. It is a variable that stands alone and isn't changed by the other variables you are trying to measure.