The diagram shows part of a food web from an estuarine wetland ecosystem.
Mummichog fish are described as both primary consumers and secondary consumers. Explain why.
Herons are described as both predators and competitors of blue crabs. Explain why.
Identify one organism in the food web that occupies the second trophic level.
Marsh snails and grass shrimp are both small estuarine invertebrates. In a habitat restoration project, scientists placed artificial refuge tiles at different tidal elevations (height above the low-tide mark) to provide shelter for these organisms.
The table shows how many tiles at each elevation were occupied by each species.
| Elevation above low-tide mark (m) | Number of tiles occupied by Marsh snails | Number of tiles occupied by Grass shrimp |
|---|---|---|
| 0.2 | 3 | 9 |
| 0.6 | 8 | 10 |
| 1.0 | 15 | 9 |
Describe the key features required to draw a bar chart on graph paper to represent these results.
The food web shows that mummichog fish feed on marsh snails, and blue crabs feed on grass shrimp. Mummichog fish can only hunt in deeper water (lower tidal elevations), whereas blue crabs can hunt across all tidal elevations. How can this be used to explain the results of the scientists' investigation?