9. A class wanted to test the effect of increasing CO2 concentration on the amount of oxygen produced by photosynthesis. They placed elodea plants in 4 test tubes containing water at 25°C. They filled each tube with fresh
water. Test tube 1 received 0.6g of baking soda to supply CO2. Test tube 2 received 0.4g of baking soda Test tube
3 received 0.2g of baking soda. Test tube 4 received 0.0g of baking soda. A collection tube was placed over each
test tube to collect the oxygen gas. The light source was placed 30 cm away from the test tube.
a. What is the independent variable?
b. What is the dependent variable?
c. What is the control?
d. What are 2 constants?
e. If photosynthesis is occurring, should the amount of oxygen be increasing or decreasing? Explain.
3

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

answer: the correct option is d. enzyme

lactase and carbonic anhydrase are the examples of enzymes.

lactase is an enzyme, which is present in the small intestine of mammals. it in the digestion of the disaccharide, lactose ( milk sugar) by converting it into two monosachharide, which are glucose and galactose.

carbonic anhydrase is present in the red blood cells. this enzyme plays significant role in the transport of co₂. it in the conversion of co₂ and h₂o into carbonic acid, which is then dissociated into bicarbonate ions and hydrogen ions.