Ecosystems and Ecological Relationships MCQs

More than two of the listed groups contain parasitoid species. Parasitoid wasps, parasitoid flies, and certain carabid beetles all exhibit parasitoid behaviour.

Centipedes are predators, not parasitoids, and termites are social detritivores. Only three of the five groups contain parasitoid species.

Neither centipedes nor termites have parasitoid species. Centipedes are free-living predators and termites are colonial detritivores.

While weathering of silicate rocks does slowly draw down atmospheric CO2, the main inputs to the carbon cycle are volcanic outgassing, respiration, and decomposition rather than rock weathering.

The nitrogen cycle is driven primarily by atmospheric nitrogen fixation (biological and lightning-mediated), not by rock weathering.

Though sulphur is present in rocks, the sulphur cycle receives major inputs from volcanic emissions and decomposition of organic matter in addition to weathering.

Copepods are zooplankton that graze on phytoplankton; they are primary consumers, not producers. Cyanobacteria are indeed primary producers.

Foraminifera are heterotrophic protists that feed on organic matter and small organisms; they are not primary producers. Diatoms are primary producers.

Both copepods and foraminifera are consumers. Copepods are crustacean zooplankton and foraminifera are heterotrophic protists.

Crustaceans are consumers and cannot be the starting point of a food chain. Primary producers (diatoms) must come first.

Herrings do not typically feed directly on diatoms; they consume zooplankton such as crustaceans. The trophic order is producers then primary consumers then secondary consumers.

This reverses the energy flow. In a food chain, energy moves from producers to consumers, not from crustaceans to herrings to diatoms.

While some lichens contain cyanobacteria as photobionts, the classic and most common lichen association is between algae and fungi, not algae and bacteria alone.

The fungal component is correct, but the photosynthetic partner in most lichens is a green alga, not a bacterium. Some lichens do contain cyanobacteria, but the standard description is algae and fungi.

Mosses are not a component of lichens. Mosses are bryophytes that may colonise rocks after lichens in the successional sequence but are not symbionts within lichens.

Viruses are obligate intracellular parasites that cannot independently decompose organic matter. They lack metabolic machinery for decomposition.

Viruses are not decomposers. While bacteria are major decomposers, viruses require living host cells to replicate and do not break down dead organic matter.

Viruses lack the enzymes and metabolic pathways needed for decomposition. Only fungi and bacteria function as decomposers in ecosystem food chains.

Statement 2 is incorrect. Food chains involve different species across trophic levels, not individuals within a single species population.

Statements 2 and 3 are both incorrect. A food chain links different species, not members of one population, and it does not quantify how many organisms are consumed.

Statement 1 is a correct and standard definition of a food chain, so 'none' is wrong.

While insects and fungi affect plant health, they are not the primary factors preventing tree establishment in grasslands. The dominant constraints are abiotic.

Grasslands typically receive ample sunlight. Nutrient levels in grassland soils are often high. The real limiting factors are moisture deficit and periodic fires.

Water limitation and fire are well-established ecological factors that maintain grassland ecosystems and prevent succession to forest.

Statement 2 is incorrect. Primary succession is actually much slower than secondary succession because the substrate lacks soil, organic matter, and seed banks.

Statement 2 is wrong. Primary succession is slower because the pioneer community must build soil from scratch, while secondary succession benefits from residual soil and seed banks.

Statement 2 is factually incorrect. Primary succession takes centuries to millennia precisely because soil must develop from scratch without pre-existing organic matter.

Obligate mutualism is a different concept. Protocooperation specifically involves a non-obligate, facultative mutualism.

A competitive interaction where both are harmed is interspecific competition, not protocooperation.

Predator-prey dynamics are a separate ecological interaction from mutualistic cooperation.

High species diversity and complex food webs are indeed characteristic of climax communities with well-developed ecological niches.

Climax communities have large standing biomass accumulated over the successional process.

Stability and self-sustaining nature are defining characteristics of a climax community.

Pairs 3 and 4 are also correct in the typical grassland food chain: grass - grasshopper - frog - snake - hawk.

Pair 4 is also correct. In the chain grass-grasshopper-frog-snake-hawk, the hawk eating the snake is at the fourth consumer (quaternary) level.

All four pairs are correctly matched within the standard grassland food chain example used in ecology textbooks.