Question

1. a student sets up the following materials, places them in a window, and observes them for two weeks. the name of the plant is elodea. a snail placed in a closed test - tube will survive longer with elodea than without elodea. a snail and elodea, placed in a closed test - tube, need air to survive. if elodea is put into a closed test - tube, the level of carbon dioxide in the water will increase. if a snail is put into a closed test - tube, the level of carbon dioxide in the water will decrease.

Explanation:

Step1: Recall photosynthesis and respiration concepts

Elodea is a plant that can perform photosynthesis. Snails perform respiration. During photosynthesis, plants take in carbon - dioxide and release oxygen. During respiration, animals take in oxygen and release carbon - dioxide.

Step2: Analyze each option

• Option 1: In a closed test - tube, the elodea can produce oxygen through photosynthesis during the day. So a snail placed in a closed test tube will survive longer with elodea than without elodea as it has a source of oxygen. This is correct.
• Option 2: While it is true that both a snail and elodea need air (oxygen for respiration and carbon - dioxide for photosynthesis respectively), this is a very general statement and does not specifically address the relationship between them in the context of the experiment.
• Option 3: If elodea is put into a closed test tube, it will take in carbon - dioxide for photosynthesis, so the level of carbon - dioxide in the water will decrease, not increase.
• Option 4: When a snail is put into a closed test tube, it respires and releases carbon - dioxide, so the level of carbon - dioxide in the water will increase, not decrease.

Answer:

A snail placed in a closed test tube will survive longer with elodea than without elodea.