Earthworm Role in Soil Ecology

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Questions and Answers

Given the role of earthworms in ecosystems, which of the following scenarios would most likely occur if earthworm populations drastically declined in a temperate forest?

An immediate and significant increase in the population sizes of robins and other earthworm predators due to the temporary abundance of their primary food source
A decrease in the overall rate of nutrient cycling, leading to a build-up of undecayed organic matter and a reduction in plant growth due to nutrient unavailability. (correct)
A shift in plant species composition towards those adapted to highly compacted soils with poor aeration, favoring species with shallow root systems.
An increase in the population of animals that primarily consume decaying organic matter other than plants, such as certain types of fungi and bacteria, leading to accelerated decomposition rates.

Considering the ecological functions of earthworms, which long-term effect would their absence most likely have on soil structure and water dynamics?

Increased soil porosity due to other organisms compensating for earthworm activity, leading to enhanced water infiltration and reduced surface runoff.
Decreased soil aeration and increased compaction, resulting in reduced water infiltration and increased risk of surface runoff and erosion. (correct)
A gradual increase in soil pH as undecayed organic matter accumulates, creating alkaline conditions that benefit certain plant species.
Enhanced aggregation of soil particles by fungal hyphae, improving soil stability and compensating for the lack of earthworm burrowing.

If a new pesticide is introduced that is highly toxic to earthworms, but not to other soil organisms, what is the most likely long-term consequence on the local ecosystem's food web?

A trophic cascade leading to a reduction in predator populations that rely on earthworms as a primary food source, such as certain bird and amphibian species. (correct)
A shift in plant community composition towards species that are less dependent on nutrient-rich soils, thus stabilizing the primary producer level.
Enhanced decomposition rates due to the proliferation of pesticide-resistant bacteria and fungi that can more efficiently break down organic matter.
An increase in the biomass of other soil invertebrates that consume decaying organic matter, compensating for the loss of earthworms in the food web.

In an experiment simulating the effects of earthworm disappearance, two identical plots of land are set up: one with earthworms and one without. Which of the following hypotheses would best predict the outcome regarding plant nutrient uptake?

The plot without earthworms will exhibit lower plant nutrient uptake due to reduced availability of nutrients in plant-accessible forms. (D) Signup and view all the answers

Considering the physical characteristics of earthworms, how does their segmented body plan specifically contribute to their ability to thrive in diverse soil environments?

It enables precise control over localized muscle contractions, facilitating movement and burrowing through soils of varying density and composition. (A) Signup and view all the answers

Given that earthworms consume their body weight in organic matter daily, what is the most likely consequence if an invasive plant species with slow decomposition rates becomes dominant in an earthworm habitat?

A decrease in earthworm population due to the low nutritional value and slow breakdown of the invasive plant matter. (D) Signup and view all the answers

How would the introduction of a non-native earthworm species into a previously earthworm-free forest most likely affect the native ecosystem's soil structure and plant community?

Disruption of the native soil structure and a decline in native plant diversity due to altered decomposition rates and nutrient availability. (A) Signup and view all the answers

If a scientist discovers a new species of earthworm that thrives in highly acidic soils, what inference can be made about its potential impact on nutrient availability in such environments?

It would likely increase nutrient availability by enhancing the decomposition of organic matter under acidic conditions. (B) Signup and view all the answers

Flashcards

Earthworm Characteristics

Earthworms are invertebrates with segmented bodies covered in slimy skin, living in temperate and tropical soils.

Earthworm Diet

Earthworms consume decaying plant matter in the soil.

Worm Castings

Earthworms break down organic matter and produce castings, which enrich soil with essential nutrients.