Minnows are mainly carnivorous, eating insects and other small animals. However, herbivory has evolved independently in minnows several times. What changes in digestive structure and function are associated with the evolution of herbivory? Which minnows, herbivorous or carnivorous, should exhibit higher cellulase activity in the gut? Explain.

Verified step by step guidance

1. Step 1: Understand the dietary habits of minnows. Carnivorous minnows primarily consume insects and other small animals, while herbivorous minnows have evolved to eat plant matter. This difference in diet will necessitate different digestive structures and functions.
2. Step 2: Recognize the changes in digestive structure and function associated with herbivory. Herbivorous minnows would need a longer gut to increase the time for digestion and absorption of nutrients from plant matter, which is harder to break down than animal matter. They would also need specialized gut bacteria to help break down cellulose, a complex carbohydrate found in plant cell walls.
3. Step 3: Understand the role of cellulase. Cellulase is an enzyme that breaks down cellulose into simpler sugars. It is produced by certain bacteria in the gut.
4. Step 4: Determine which type of minnow should exhibit higher cellulase activity. Given that cellulase is needed to break down plant matter, herbivorous minnows should exhibit higher cellulase activity in the gut than carnivorous minnows.
5. Step 5: Explain the reasoning. Herbivorous minnows consume a diet rich in plant matter, which contains cellulose. To digest this cellulose, they rely on gut bacteria that produce cellulase. Therefore, herbivorous minnows should have higher cellulase activity in their gut compared to carnivorous minnows, who consume a diet primarily of insects and other small animals, which do not contain cellulose.