What is meant by the term gas exchange?
Trout rely on gills as their gas exchange surface. Describe three anatomical adaptations of fish gills that facilitate rapid and efficient gas exchange.
A group of marine biology students investigated how water temperature affects the opercular beat rate (OBR)—a measure of ventilation rate—in juvenile rainbow trout (Oncorhynchus mykiss). They placed individual fish of the same mass in tanks of water maintained at different constant temperatures. The ventilation rate was determined by counting the number of opercular movements per minute.
The results of the investigation are shown in the table below:
| Water temperature (∘C^{\circ}\text{C}∘C) | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Average |
|---|---|---|---|---|---|
| 4 | 15 | 13 | 14 | 14 | 14 |
| 8 | 28 | 31 | 30 | 27 | 29 |
| 12 | 49 | 52 | 50 | 53 | Y |
| 16 | 76 | 73 | 75 | 76 | 75 |
| 20 | 104 | 101 | 103 | 104 | 103 |
Calculate the missing average, YYY, for a water temperature of 12 ∘C12\text{ }^{\circ}\text{C}12 ∘C.
Explain how these experimental results support the physiological theory that the concentration of dissolved oxygen in water decreases as the water temperature increases.
The students controlled the mass of the juvenile trout. Explain why this is necessary to ensure a valid investigation.
State two other variables, other than the mass of the fish, that the students should have controlled during this investigation.
