Which of the following was a dependent variable in Experiment 1?
","rationale_html":null,"correct_answer":["B"],"equiv_key":null,"has_media":true,"has_mathml":false,"has_table":false,"section_label":"Science","options":[{"label":"A","content_html":"percula
","ord":0},{"label":"B","content_html":"Specific growth rate
","ord":1},{"label":"C","content_html":"Diet fed to the
","ord":2},{"label":"D","content_html":"Stocking density of the
","ord":3}],"passage":{"id":"act_practice_pdf:pt1:science:p3","source_id":"act_practice_pdf","form_id":"act_practice_pdf:pt1","section":"science","number":"III","kind":null,"title":null,"content_html":"Amphiprion percula, a species of clownfish, are kept in many home aquariums. Two experiments were conducted to determine how diet and stocking density (number of fish per liter of seawater, fish/L) affect the specific growth rate (SGR; percent increase in length per day, percent/day) in A. percula. Experiment 1 Each of 12 identical 15 L tanks received 10 L of seawater having a salinity of 33 parts per thousand (ppt), a temperature of 27°C, and a pH of 8.2. Salinity, temperature, and pH were kept constant over the course of the experiment. A. percula of similar lengths were selected, and their lengths were measured, in cm, with a ruler. Then they were equally distributed among the tanks at a stocking density of 1 fish/L. The tanks were then divided equally into 4 groups. For 4 months, each group was fed a different diet (Diets Q−T). Each group was fed the same mass of food 3 times daily. At the end of 4 months, the length of each fish was measured, in cm, with a ruler, and the SGR of each fish was calculated. The average SGR was then determined for each group (see Table 1). Table 1 Average SGR Diet (percent/day) Q 0.30 R 0.40 S 0.50 T 0.35 Experiment 2 The procedures for Experiment 1 were repeated except that each group was kept at a different stocking density, 0.5 fish/L, 1 fish/L, 2 fish/L, or 3 fish/L, and all fish were fed Diet T. At the end of 4 months, the average SGR was determined for each group (see Table 2). Table 2 Stocking density Average SGR (fish/L) (percent/day) 0.5 0.50 1 0.35 2 0.25 3 0.20 Tables adapted from João Chambel et al., “Effect of Stocking Density and Different Diets on Growth of Percula Clownfish, Amphiprion percula (Lacepede, 1802).” ©2015 by Springer.
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