Ecology Quiz
Questions: 16 · 10 minutes
1. Several bird species live in the same trees but feed at different heights and on different parts of the branches. What is the most likely ecological effect?
The birds become members of the same population
The trees reach carrying capacity more quickly
Predation increases because each species occupies a separate niche
Resource partitioning reduces direct competition among the species
2. An isolated population contains very few individuals and little genetic variation. Why can this increase its vulnerability to environmental change?
Every individual will respond identically to all predators
The population will necessarily exceed its carrying capacity
Fewer genetic differences may limit the population's capacity to adapt to new conditions
Low variation prevents any individual from reproducing
3. Fertilizer runoff enters a lake, followed by rapid algal growth and a decline in dissolved oxygen. Which process best explains this sequence?
Eutrophication promotes algal growth, followed by decomposition that consumes oxygen
Ecological succession replaces aquatic species with terrestrial species
Biomagnification increases the concentration of toxins at higher trophic levels
Nitrogen fixation removes oxygen as bacteria convert nitrates into nitrogen gas
4. Which description best defines an ecosystem?
All members of one species living in the same area
A community of organisms together with the nonliving environment they interact with
Every region on Earth that supports living organisms
A group of different species occupying the same area, excluding nonliving factors
5. Adding nitrogen to a pond produces little change in algal growth, but adding phosphorus causes a large algal bloom. What is the best inference?
Nitrogen is toxic to the pond's algae
Phosphorus converted the algae into primary consumers
Phosphorus was a limiting nutrient for algal growth
Nitrogen was already preventing photosynthesis
6. Which interaction is the clearest example of mutualism?
Two plant species compete for the same soil nutrients
A tick feeds on the blood of a deer
A hawk captures and eats a mouse
A bee receives nectar while transferring pollen between flowers
7. What is the main ecological role of primary producers in most ecosystems?
They recycle nutrients by breaking down dead material
They convert light or chemical energy into energy-rich organic matter
They control herbivore populations through predation
They obtain energy by consuming other organisms
8. A wildfire removes most vegetation from a grassland, but the soil and some seeds remain. What type of ecological recovery is most likely to follow?
Primary succession, because all previous organisms were disturbed
Competitive exclusion, because surviving species must share resources
Secondary succession, because an established soil layer remains
Biological magnification, because materials persist after the fire
9. Which factor is most likely to become stronger as a population grows more crowded?
A volcanic eruption
A sudden seasonal frost
Transmission of an infectious disease
A hurricane crossing the habitat
10. A large forest is cleared and much of its vegetation is burned. What is the most likely immediate effect on the carbon cycle?
Atmospheric carbon dioxide increases because stored carbon is released and plant uptake is reduced
Carbon fixation increases because fewer plants compete for sunlight
Atmospheric carbon dioxide decreases because exposed soil absorbs more carbon
Carbon stops moving through the ecosystem until new trees mature
11. A cool-adapted mountain species already lives near the warm edge of its temperature tolerance. If local temperatures rise over many years, which response is most plausible when suitable habitat is available?
Its range shifts toward higher, cooler elevations
It immediately changes into a warm-adapted species
Its trophic level increases as temperatures rise
Its range shifts downhill toward warmer elevations
12. What distinguishes a keystone species from most other species in a community?
It always occupies the highest trophic level in a food web
It has a disproportionately large effect on community structure relative to its abundance
It is the most numerous species in the ecosystem
It can survive without interacting with other species
13. A deer population grows rapidly, then levels off as food and habitat become limited. What does the stable population level most closely represent?
The population's minimum viable size
The ecosystem's trophic level
The population's geographic range
The environment's carrying capacity
14. During one month, a population has 30 births, 20 deaths, 5 immigrants, and 10 emigrants. How does the population size change?
It increases by 5 individuals
It remains unchanged
It decreases by 15 individuals
It increases by 25 individuals
15. Researchers mark 40 turtles, release them, and later capture 50 turtles, including 10 marked individuals. Assuming the samples mixed well and marking did not affect capture, what population estimate does the mark-recapture method give?
100 turtles
200 turtles
500 turtles
2,000 turtles
16. Why is less energy generally available to organisms at higher trophic levels?
Consumers cannot digest any material produced at lower trophic levels
Producers use nearly all available energy to absorb soil nutrients
Energy is destroyed whenever one organism consumes another
Organisms use much of the energy they obtain for metabolism, with some lost as heat