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#predators

3 public questions tagged with this topic.

Controls Ecosystem

Removal of top predators leads to:

“Increased prey populations” for removal of top predators leads to. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Coexistence requires stabilizing differences that make each species limit itself more strongly than it limits its competitor, or an equalizing process that keeps fitness differences small. Without such mechanisms, persistent competitive asymmetry tends toward exclusion. The remaining alternatives—“Decreased prey populations”, “Increased stability”, “No ecosystem impact”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Evidence should connect encounter rates or resource use to survival, growth, or reproduction. The ecological label follows that causal effect rather than superficial proximity between organisms. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.

Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 4

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Controls Ecosystem

Predators influence lower trophic levels through:

“Predation” for predators influence lower trophic levels through. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Evidence should connect encounter rates or resource use to survival, growth, or reproduction. The ecological label follows that causal effect rather than superficial proximity between organisms. The remaining alternatives—“Competition”, “Nutrient cycling”, “Mutualism”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Species interactions are classified by their net effects on the fitness of each participant, but those effects can change with density, resource supply, life stage, and environmental stress. Competition reduces access to shared limiting factors, whereas predation and parasitism transfer resources from victim to consumer. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.

Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 4

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SPECIES INTERACTION

Grazers differ from predators because:

Grazers typically consume parts of many prey individuals during their lifetime and usually do not kill each individual outright. A cow removes grass leaves, or a caterpillar eats portions of several plants, leaving the resource organism capable of survival and regrowth. A true predator also commonly attacks multiple prey, but it normally kills each prey individual during a discrete feeding event. Thus, feeding on multiple “hosts” is not by itself unique to grazers; the item’s intended contrast is that grazers repeatedly exploit multiple living organisms rather than maintaining a prolonged association with one host. Parasites generally live in or on one or a few hosts, derive resources over an extended period, and ordinarily avoid rapid host death. Symbiosis is also not required for grazing. The keyed statement is acceptable only in this comparative sense and is imprecisely worded because predators also consume multiple prey. The stronger biological distinction is partial consumption without immediate death, together with movement among many resource individuals.

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 8-13

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