<span>Controlled variable is a variable that was made constant in the research. That was because the controlled variables can influence the dependent or independent variable. If the variables is not made constant, it can alter the research result and made it invalid.
In this case, </span>the caffeine and alcohol intake might alter the physical activity or the blood glucose so it should be controlled.
Answer:
In animal field studies, why do scientists usually try to work without making the animals aware that the humans are present? It is necessary to observe the animals without disturbing them. When a controlled experiment is not possible, why do scientists try to identify as many relevant variables as possible?
The answer is False.
Although, there are some evidence that suggests that species from million years ago possessed both gills and lungs. For example is the Acanthostega Gunnari, one of the oldest species discovered with four limbs. The creature is a salamander-like creature found in Greenland hundreds of million years ago. Although the specie can walk on land but the finding characterized the creature primarily as a fish.
