7-Community Ecology 2

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Questions and Answers

How does the introduction of large top predator fishes affect the abundance of the aquatic plant community in a system with strong top-down control?

Increase nutrient levels, thus promoting aquatic plants

Decrease the abundance of aquatic plants (correct)

Increase the abundance of aquatic plants

Have no effect on aquatic plants

What is a common challenge faced by restoration projects aimed at recovering ecological communities?

They have no impact on the ecosystem

They often lead to species invasions

They are always successful with enough funding

They are expensive and many fail (correct)

Why might fox-free islands appear greener in the Aleutian Islands case study?

Reduced soil erosion

Increased water availability

Less competition among plant species

Higher populations of flora without herbivory (correct)

What concept describes the phenomenon where indirect effects create misleading ecological patterns?

Apparent Competition Signup and view all the answers

In the context of biomanipulation, what type of control involves altering the abundance of top consumers to influence lower trophic levels?

Top-down Control Signup and view all the answers

What kind of ecological change can species invasions lead to?

Increase in species extinction rates Signup and view all the answers

What might happen to vegetation if a new squirrel species, which shares a predator, is introduced into the ecosystem?

No change in vegetation levels as they eat different plants Signup and view all the answers

What are the direct effects in a trophic cascade?

Impact of predators on their prey Signup and view all the answers

What is a key characteristic of a trophic cascade?

Changes in one trophic level can significantly impact others. Signup and view all the answers

In a food web, which of the following describes direct effects?

The immediate impact of one species' behavior on another. Signup and view all the answers

Which model suggests that populations are regulated by the availability of energy and nutrients?

Bottom-up regulation Signup and view all the answers

What does the term 'apparent competition' refer to?

Indirect competition caused by shared predation threats. Signup and view all the answers

How do arrows in food webs function?

To indicate the direction of energy flow. Signup and view all the answers

Why might an increase in zebra food be a viable option for managing zebra populations?

It facilitates bottom-up regulation of the ecosystem. Signup and view all the answers

What is indicated by 'top-down' population regulation?

Predators limit the population size of their prey. Signup and view all the answers

What is described by the term 'trophic structure'?

The interactions between various trophic levels based on feeding relationships. Signup and view all the answers

Study Notes

Community Ecology II: Direct and Indirect Effects in Food Webs

Food webs depict complex feeding relationships within an ecosystem
Trophic structure describes who eats whom, transferring energy and nutrients
Direct effects – immediate effects between two species in a food web
Indirect effects – delayed impacts between two species in a food web
Apparent competition – a phenomenon where two species are seemingly competing for resources but are indirectly affected through a predator-prey relationship
Top-down control – the abundance of species in a food web regulated by higher trophic levels (e.g., predators); predators control prey populations
Bottom-up control – the abundance of species in a food web regulated by lower trophic levels (e.g., producers); producers control populations at higher trophic levels
Restoration projects aim to recover ecological communities and their functions by methods like planting seeds or saplings.
Restoration projects are often expensive and can fail; this highlights the complexity of food webs
Real-world food webs often change due to species introductions, invasions, extinctions, and nutrient/resource level shifts.
Introduced species, like foxes in the Aleutian Islands, may lead to changes in abundance of other species (e.g., seabirds and vegetation).
The removal of top-level predators, can have a positive effect on vegetation abundance in some systems, like in the Yellowstone National Park with the reintroduction of wolves increasing the populations of other species.

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