Ecology and Ecosystems Quiz

What is the primary difference between a habitat and a niche?

• A habitat is where an organism lives, while a niche is what it eats

• A habitat includes both biotic and abiotic factors where an organism lives, while a niche is its role and interactions in the ecosystem

• A habitat is only the physical space, while a niche is only the food source

• A habitat and niche are the same thing

Answer explanation

The correct choice highlights that a habitat encompasses both biotic and abiotic factors where an organism lives, while a niche refers to its specific role and interactions within the ecosystem.

Which type of symbiotic relationship describes a situation where one organism benefits while the other is unaffected?

• Mutualism

• Parasitism

• Commensalism

• Competition

Answer explanation

Commensalism is the type of symbiotic relationship where one organism benefits while the other is neither helped nor harmed. This distinguishes it from mutualism, where both benefit, and parasitism, where one benefits at the other's expense.

What determines the number of predators in an ecosystem?

• The amount of sunlight available

• The availability of prey

• The temperature of the environment

• The size of the ecosystem

Answer explanation

The number of predators in an ecosystem is primarily determined by the availability of prey. More prey supports a larger predator population, while limited prey restricts predator numbers.

How is population density calculated?

• Total area divided by number of organisms

• Number of organisms multiplied by area

• Number of organisms divided by total area

• Number of deaths minus number of births

Answer explanation

Population density is calculated by dividing the number of organisms by the total area they occupy. This gives a measure of how many individuals live in a specific unit of area, making the correct choice: 'Number of organisms divided by total area'.

What characterizes clumped dispersion in a population?

• Organisms are evenly spaced throughout the habitat

• Organisms are randomly scattered in the environment

• Organisms gather in groups for protection or resources

• Organisms maintain equal distances from each other

Answer explanation

Clumped dispersion occurs when organisms gather in groups, often for protection or to access resources more effectively. This behavior contrasts with even spacing or random distribution, making the correct choice the one that highlights grouping.

What is a keystone species?

• The most numerous species in an ecosystem

• A species that has a disproportionately large effect on its ecosystem

• The largest predator in an ecosystem

• Any species that produces its own food

Answer explanation

A keystone species is one that has a disproportionately large effect on its ecosystem, meaning its presence or absence significantly impacts the structure and function of the environment, unlike the most numerous or largest species.

In a food chain, what percentage of energy is typically transferred to the next trophic level?

• 1%

• 10%

• 50%

• 90%

Answer explanation

In a food chain, only about 10% of the energy from one trophic level is transferred to the next. This is known as the 10% rule, as energy is lost at each level due to metabolic processes and heat.

What is an autotroph?

• An organism that eats only plants

• An organism that eats only animals

• An organism that produces its own nutrients

• An organism that decomposes dead matter

Answer explanation

An autotroph is an organism that produces its own nutrients, typically through photosynthesis or chemosynthesis, rather than consuming other organisms. This distinguishes them from those that eat plants or animals.

What process is primarily responsible for removing CO2 from the atmosphere?

• Cellular respiration

• Decomposition

• Photosynthesis

• Evaporation

Answer explanation

Photosynthesis is the process by which plants, algae, and some bacteria convert carbon dioxide (CO2) and sunlight into glucose and oxygen, effectively removing CO2 from the atmosphere.

What is biomagnification?

• The increase in population size over time

• The accumulation of toxins up the food chain

• The growth of plants in response to sunlight

• The process of making microscopic organisms visible

Answer explanation

Biomagnification refers to the accumulation of toxins in organisms as they move up the food chain. This means that predators at higher levels can have much higher concentrations of harmful substances than those at lower levels.