Statement Analysis

1. Herbivores Enhance the Productivity of a Productive Ecosystem and Reduce the Productivity of an Unproductive Ecosystem

This statement is nuanced but not strictly incorrect. In some productive ecosystems, herbivores can stimulate plant growth through grazing, which promotes regrowth and nutrient cycling, thereby enhancing overall productivity. In contrast, in unproductive ecosystems with limited plant biomass, herbivores may further reduce productivity by consuming the scarce resources. While this is a generalization, it is supported by some ecological studies and is not considered incorrect.

2. Detritus-Based Food Chains Are Longer in More Productive Ecosystems

There is no clear evidence to support this statement. The length of detritus-based food chains is influenced by factors such as resource quality, decomposition rates, and the diversity of decomposers and detritivores, rather than overall ecosystem productivity35. Detritus food chains can be found in both productive and unproductive environments, and their length is not necessarily greater in more productive ecosystems.

3. Consumption Efficiency of Herbivores Is Higher in Grasslands Than Ocean

This statement is incorrect and contradicts established ecological understanding. Consumption efficiency refers to the proportion of primary production consumed by herbivores. In aquatic (ocean) ecosystems, phytoplankton are small, highly digestible, and rapidly consumed by zooplankton, resulting in high consumption efficiency. In contrast, in terrestrial (grassland) ecosystems, a lower proportion of plant biomass is consumed by herbivores due to structural defenses and lower digestibility. Therefore, consumption efficiency is generally much higher in ocean herbivores than in grassland herbivores.

4. Production Efficiency of Carnivores Is Higher Than Herbivores

This statement is oversimplified and not universally correct. Production efficiency is the proportion of assimilated energy converted into new biomass. Among vertebrates, ectothermic carnivores (like snakes or spiders) may have higher production efficiencies than herbivores (often endotherms like mammals), but this is not a standard ecological generalization. In general, production efficiency depends on the organism’s thermal strategy and metabolic rate, and is not simply higher for carnivores than for herbivores.

Summary Table

Conclusion

The most clearly incorrect statement is:

(3) Consumption efficiency of herbivores is higher in grasslands than ocean

This directly contradicts established ecological knowledge that consumption efficiency is higher in aquatic (ocean) herbivores than in terrestrial (grassland) herbivores.