Which scientific investigation does not include dependent and independent variable?
1.observing and counting bird populations
2.studying the effect of temperature on bacterial reproduction rates
3.investigating the effect of mass on the speed at which an object falls
4.testing a model car's air flow resistance at different wind speeds in a wind tunnel

Factors that can increase mutation rates a. high temps b. low temps c. food additives d. uv rays

Aresearcher designed an investigation to test what effect eating different types of food would have on blood insulin levels. she selected 10 male subjects who were all 25 years of age and in good health. the experiment took place over 3 days. at 8: 00 a. m. on each day, the subjects ate a meal consisting of only 1 type of food. they had their blood insulin levels measured after consuming the meal. on day 1 they ate a high fat diet, on day 2 they ate a high protein diet, and on day 3 they ate a high sugar diel what is the independent variable in this experiment? a the age of the subjects b the blood insulin level c the type of food consumed d the time of day the meal was consumed

9. the history of life on earth is recorded in