Ecology Quiz

What causes trophic cascades?

• Increasing the number of producers

• Pollution

• The removal of a keystone species

• Introducing a new species to an ecosystem

Answer explanation

Trophic cascades occur when a keystone species is removed, disrupting the balance of the ecosystem. This can lead to overpopulation of prey species and a decline in plant life, affecting the entire food web.

What types of organisms are producers?

• autotrophs

• apex predators

• heterotrophs

• keystone species

Answer explanation

Producers are organisms that can make their own food through photosynthesis or chemosynthesis. Autotrophs, such as plants and some bacteria, are the primary producers in ecosystems, while apex predators and heterotrophs rely on others for energy.

What are limiting factors?

• The maximum number of organisms an area can sustain

• Scarce resources that limit the size of a population

• Conditions that limit how much energy flows to the next trophic level

• How diverse the populations of a community are

Answer explanation

Limiting factors are scarce resources that restrict the growth of a population. They can include food, water, and space, which directly affect how many organisms an area can support.

If the producer level of an ecosystem has 750,000 J of energy, how much energy would be passed on to the secondary consumers?

• 75,000 J

• 7,500 J

• 750 J

• 75 J

Answer explanation

In an ecosystem, only about 10% of energy is transferred to the next trophic level. Therefore, 10% of 750,000 J is 75,000 J for primary consumers, and 10% of that (for secondary consumers) is 7,500 J.

What does carrying capacity mean?

• The amount of abiotic factors present in the environment

• The total number of species living in an ecosystem

• The number of offspring one mother can have in a year

• The number of organisms an ecosystem can sustain

Answer explanation

Carrying capacity refers to the maximum number of organisms an ecosystem can sustain without degrading the environment. This choice accurately defines the concept, unlike the other options which focus on different ecological aspects.

Which of the following would be a density independent limiting factor?

• A virus spreading through a population

• A forest fire burning down a forest

• Birds competing for a limited amount of seeds

• A new predator moving to an area

Answer explanation

A forest fire is a density independent limiting factor because it affects the population regardless of its density, unlike a virus or competition for resources, which depend on population size.

Which of the following would be a density-dependent limiting factor?

• Two wolf packs having overlapping territories

• Pollution

• A flood

• Deforestation

Answer explanation

Density-dependent limiting factors are influenced by population density. Two wolf packs overlapping territories can lead to competition for resources, affecting their survival. In contrast, pollution, floods, and deforestation are density-independent.

Which of these describes a mutualistic relationship?

• When one organism is harmed, but the other is benefitted

• When one organism is unaffected, and the other is harmed

• When one organism benefits, and the other is unaffected

• When both organisms involved benefit

Answer explanation

A mutualistic relationship is defined as one where both organisms involved benefit from the interaction. This distinguishes it from other types of relationships where one may be harmed or unaffected.

What is a niche?

• A species that outcompetes others in an area

• The level on a food chain an organism occupies

• An organisms role in an ecosystem and the resources they obtain

• A species that disproportionately affects an ecosystem

Answer explanation

A niche refers to an organism's role in an ecosystem, including how it interacts with other species and the resources it utilizes. This definition captures the essence of how organisms fit into their environment.

What will happen if two species occupy the same niche in an ecosystem?

• The ecosystem will be stressed and could collapse

• One species will either alter their niche or be eliminated

• The niche will expand to accommodate both species

• The species will share the niche

Answer explanation

When two species occupy the same niche, competition arises. Typically, one species will adapt by altering its niche or face elimination, as resources are limited and cannot support both species equally.