Ecology Test Questions

Please know

What is the main difference between how energy and nutrients move through ecosystems?

Energy flows through ecosystems (lost as heat), while nutrients cycle between abiotic and biotic components.

What is the difference between an ecosystem and an ecological community?

An ecosystem includes both the biotic community and the abiotic environment; a community is just the biotic part.

What term applies to the fixation of light energy into chemical energy by autotrophs?

Primary production.

What does NPP stand for?

Net Primary Productivity.

What does GPP stand for?

Gross Primary Productivity.

What is the difference between NPP and GPP?

GPP is total energy captured; NPP is GPP minus respiration (NPP = GPP – R).

NPP can be quantified by the following methods except…

(Options not given) – In general, not by measuring sunlight directly; NPP is measured by biomass changes or CO₂ uptake​.

What is the effect of temperature, precipitation, and nutrients on NPP?

NPP increases with higher temperature (because warmer conditions boost photosynthetic rates).

• NPP increases with more nutrient availability (especially nitrogen and phosphorus).

• NPP increases with moderate precipitation, but too much precipitation can cause NPP to decline because excessive water can limit oxygen availability in the soil.

Which ecosystems tend to have the greatest primary productivity?

Tropical rainforests and marshy/shallow aquatic ecosystems.

What is Net Secondary Productivity (NSP)?

The rate of consumer biomass accumulation from ingesting primary producers.

In net secondary production, where does the rest of the ingested matter and energy go besides biomass?

It’s lost through respiration/metabolism and egestion (undigested waste).

Due to ecological efficiency, what happens to the total amount of energy as you move up a food chain?

It decreases significantly—only about 10% of energy transfers to the next level.

Why is there a limit to the number of trophic levels possible in any given ecosystem?

Energy loss limits the number of higher trophic levels that can be supported.

Since the early 20th century, humans have used what strategies to boost gross primary production (GPP) in crops?

Selective breeding, genetic modification, irrigation, fertilization, and pesticide use​.

Since the early 20th century, humans have used what strategies to boost net primary production (NPP) in agricultural crops?

Fertilizers, irrigation, selective breeding, and pesticides​.

How does agriculture impact ecological systems?

It uses large amounts of land, water, chemicals, and fossil fuels, leading to habitat loss, pollution, and climate change.

If someone wants to reduce their ecological impact by changing their diet, what would you recommend?

Eat lower on the food chain — shift toward more plant-based foods (because producing meat requires more energy input).

What is the difference between grazing and detrital food chains?

Grazing food chains are based on living plant biomass (NPP), detrital food chains are based on dead organic matter.

The hydrologic cycle is driven by what processes?

Evapotranspiration, percolation, condensation and precipitation.

The carbon cycle involves which of the following processes?

Photosynthesis, respiration, decomposition, and combustion​.

Which nitrogen cycle process involves conversion of atmospheric nitrogen gas into biologically available forms? (Plus name all the processes)

Nitrogen fixation.

Fixation of N₂

biological: into ammonia (NH₃)

atmospheric: into nitrate (NO₃^-

Mineralization

decomposers convert

organic N to inorganic N (NH₄⁺)

Nitrification

bacteria convert inorganic N

ammonium to nitrite to nitrate

Denitrification

Anaerobic conditions: bacteria convert nitrate into N₂

Assimilation

Producers take up either ammonium or nitrate. Consumers take up nitrogen through eating producers.

How does the phosphorus cycle differ from other main nutrient cycles?

It has no gaseous phase — phosphorus cycles locally through land and water​.

Phosphorus is NOT a major nutrient needed by plants. (True or False?)

False — plants need phosphorus for DNA, ATP, and membranes.

Name one of the major nutrient cycles.

carbon cycle, nitrogen cycle, or phosphorus cycle.

Briefly discuss how human activities have affected one major nutrient cycle — positive and negative.

(Example: Nitrogen cycle) Humans increase nitrogen availability through fertilizers (positive: boosts crop yields; negative: causes pollution, algal blooms, and loss of biodiversity).

In terms of Earth's biodiversity, what levels of diversity were discussed?

Genetic diversity, species diversity, and ecological diversity.

Approximately what percent of total mammal biomass on Earth consists of wild terrestrial and marine mammals?

About 4% — humans and livestock make up the rest​.

The instrumental value of ecosystems, also known as ecosystem services, includes all of the following types of services except…?

(Trick: Intrinsic value is not an ecosystem service — it's separate.) The ones that count are regulatory, provisional, cultural, and supporting

Describe one explanation for why biodiversity tends to be higher near the tropics and decreases toward the poles.

The tropics have more stable climates, more sunlight, and higher energy input (higher productivity supports more species). Habitat heterogeneity.

What are the five main categories of human impacts on biodiversity?

Habitat loss, Invasive species, Pollution, Overharvesting, and Climate change (remember: HIPOC​).

Which of the five human impacts is the largest cause of biodiversity decline worldwide?

Habitat loss.

What are the three main ways habitat can be lost?

Destruction, fragmentation, and degradation.

What is the difference between bioaccumulation and biomagnification?

Bioaccumulation = buildup of toxins in an individual over time; Biomagnification = increase of toxin concentration as you move up trophic levels.

What is the difference between background extinction and mass extinction?

Background extinction = natural, low rate of species loss; Mass extinction = when >75% of species go extinct within a 2-million-year period.

How many times higher is the current extinction rate compared to background rates?

About 1,000 times higher​.

Are we currently experiencing another mass extinction event? Explain.

Yes, human activities have accelerated extinction rates so dramatically that we may be triggering the 6th mass extinction​.

What is the term for releasing captive-bred or wild-collected individuals onto part of their historic range where the species no longer exists?

Species reintroduction.

What term describes efforts to recreate, initiate, or accelerate the recovery of an ecosystem that has been disturbed?

Ecological restoration.

Over the last 50+ years, what trend has the percentage of legally protected habitats followed?

It has increased steadily​.

Why are ecology and evolution part of the biology curriculum?

They are major unifying concepts — populations evolve in response to ecological challenges, helping explain why organisms are the way they are​.

Natural selection acts at the level of the , whereas evolution acts at the level of the .

Natural selection acts at the level of the individual, evolution acts at the level of the population.

What is the original source of all genetic variation in a population?

Mutation.

Which of these statements best describes a biome?

A geographic region characterized by a distinct set of climate conditions and major plant forms.

Aquatic biomes are most frequently characterized by what factors?

Salinity, flow (lentic vs lotic), and depth.

What is a heritable trait of an organism that has evolved by natural selection called?

An adaptation.

What is the definition of a population?

A group of individuals of the same species living in the same area at the same time.

What is the definition of a community?

A group of interacting species living together in the same area.

What is the definition of an ecosystem?

A community of organisms and their abiotic environment interacting together.

In logistic growth, what is the maximum number of individuals that can be supported long-term in the environment called?

Carrying capacity (K).

In logistic growth, at what population size does the population experience the highest growth rate?

At half the carrying capacity (K/2).

In logistic growth, at what population size is the per capita growth rate closest to the intrinsic growth rate?

When the population size is very small (near 0).

In the logistic growth model, what is the parameter referred to in question 45 (maximum population size)?

Carrying capacity (K).

In the logistic growth model, what is the parameter referred to in question 46 (per capita growth rate)?

Intrinsic growth rate (r).