<span>there are two types of speciation: allopatric and sympatric. For allopatric speciation there must be a geographical separation between two populations (a mountain for example). For sympatric speciation there are a LOT of possible barriers. Hope this helps! </span>
I think its pulmonary circulation too.
Answer:
<em>Controlled variables</em>
Explanation:
In a controlled experiment, the control group and the experimental groups are the same except for a factor in the experimental groups called a. variable parameter. In a controlled experiment, the factors that are kept the same between groups are called. controlled parameters.