Marine Biology: Trophic Cascades Quiz

All members of a food web are equal in abundance and on their relative effects on one another.

Explain the reasoning to why 'all members of a food web are equal in abundance and on their relative effects on one another' is false.

Every member of a food web is the prey of another member of the food web.

Why are the mussels in Mukkaw Bay able to quickly cover the rockface in Paine's experiment?

How did the green world hypothesis differ from the 'bottom-up' view?

Imagine a simple food chain: Grass -> Grasshoppers -> Mice. If snakes that eat mice are added to this ecosystem, how would you redraw the food chain to represent this change?

After the snakes are added, would you expect the amount of grass to increase or decrease? Explain your reasoning.

In 1997, which species is the apex predator in the food chain?

Draw two diagrams that show the food chains for the control and experimental plots. Include interactions among predatory beetles (if present), ants, caterpillars, and piper plants.

What statement do Letourneau and Dyer's results support?

Do the results of the Letourneau and Dyer experiment support or refute the green world hypothesis? Explain your answer.

Food Web Dynamics

Not all members of a food web have equal effects on one another; some species can significantly influence ecosystem structure despite lower abundance.
Apex predators are positioned at the top of food webs and typically do not have predators themselves.

Keystone Species

Removal of keystone species (e.g., starfish) can lead to dramatic declines in biodiversity; mussels proliferated when their predator was removed in Paine's experiment.
After the starfish removal, species diversity in the ecosystem decreased from 15 to nearly all mussels, indicating the crucial role of keystone species in maintaining ecological balance.

Green World Hypothesis vs. Bottom-Up View

The green world hypothesis posits that herbivore populations are regulated by predation, challenging the bottom-up perspective that emphasizes resource availability as the main control factor.

Food Chain Dynamics

Introducing snakes to a simple food chain (Grass -> Grasshoppers -> Mice) modifies it to Grass -> Grasshoppers -> Mice -> Snakes, illustrating the impact of predators.
The presence of snakes would likely lead to a decrease in mouse populations, resulting in an increase in grasshoppers, which would then consume more grass.

Apex Predators

In the 1997 ecosystem scenario, killer whales were recognized as apex predators, playing a significant role in controlling other population sizes in marine food webs.

Trophic Cascades

Adding predatory beetles to food chains resulted in reduced ant populations, triggering cascades affecting plant health by decreasing leaf area.
The experiment conducted by Letourneau and Dyer supports the green world hypothesis, demonstrating that top-down predation by beetles impacts herbivore (caterpillar) populations and subsequently plant health.

Summary of Experimental Results

Control plots showed stability with no significant changes in species diversity, contrasting with experimental plots where the removal of predators led to ecological imbalances.
Key interactions among species, including predatory relationships, highlight the interconnectedness of food web dynamics.

Test your knowledge about trophic cascades and the role of keystone species in marine ecosystems. This quiz will challenge your understanding of food webs and the relative impacts of different species on their environment. Get ready to delve into the intricacies of marine biology!