Question 1

A researcher wants to test the effect of fertilizer on plant growth. She applies different amounts of fertilizer to separate plots and measures the height of plants after 8 weeks. Which of the following best identifies the independent and dependent variables in this experiment?

Accepted Answer

Independent variable: amount of fertilizer; Dependent variable: plant height

Question 2

A scientist observes the migration patterns of birds over several years without interfering. What type of study is this, and why?

Accepted Answer

Observational study, because the scientist is only recording natural events

Question 3

If the pH of a freshwater lake drops from 7 to 5 due to acid rain, what is the most likely effect on the proteins of aquatic organisms?

Accepted Answer

Proteins may denature, losing their structure and function

Question 4

Why does oil float on water in an ecosystem after a spill?

Accepted Answer

Oil is nonpolar and less dense than water, so it does not mix and floats

Question 5

A drought causes only plants with deep roots to survive in a grassland. Over several generations, what evolutionary change is most likely in the plant population?

Accepted Answer

Plants with deep roots will become more common due to natural selection

Question 6

A river changes course and separates a population of frogs into two groups. Over time, these groups develop different mating calls and can no longer interbreed. What process has occurred?

Accepted Answer

Allopatric speciation

Question 7

A population of rabbits in a field grows rapidly at first, then levels off as food becomes scarce. Which equation best describes the population's growth as it approaches carrying capacity $$K$$?

Accepted Answer

$$\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$$

Question 8

Which of the following is an example of mutualism?

Accepted Answer

Bees pollinating flowers while collecting nectar

Question 9

When two species compete for the same limited resource and one is eliminated from the habitat, what principle is illustrated?

Accepted Answer

Competitive exclusion

Question 10

In a kelp forest, sea otters are removed by hunting. As a result, sea urchin populations explode and kelp forests decline. What is this an example of?

Accepted Answer

Trophic cascade

Question 11

After a volcanic eruption covers land with lava, what is the first stage of ecological recovery called?

Accepted Answer

Primary succession

Question 12

A government imposes a tax on companies for each ton of carbon dioxide they emit. What type of policy tool is this?

Accepted Answer

Green tax

Question 13

A factory pollutes a river, causing health problems for people downstream who do not benefit from the factory's products. What economic concept does this illustrate?

Accepted Answer

Externality

Question 14

A country has an age-structure diagram shaped like a pyramid, with a broad base and narrow top. What does this indicate about its population?

Accepted Answer

The population is rapidly growing, with many young people

Question 15

A farmer irrigates his fields heavily, leading to a buildup of salts in the soil. What is this process called, and what is a likely consequence?

Accepted Answer

Salinization; reduced soil fertility

Question 16

Which of the following is a tradeoff associated with using feedlots for meat production?

Accepted Answer

Feedlots increase energy efficiency but can lead to concentrated waste and water pollution

Question 17

A scientist wants to test if a new pesticide affects bee populations. She sprays some fields with the pesticide and leaves others untreated, then counts bee numbers in both. Which field is the control group?

Accepted Answer

The untreated fields

Question 18

Which scenario best illustrates resource partitioning?

Accepted Answer

Two bird species feed at different heights in the same tree to avoid competition

Question 19

Which of the following best describes the main difference between primary and secondary succession?

Accepted Answer

Primary succession starts with bare rock and no soil; secondary succession starts where soil is already present

Question 20

Which of the following is a likely outcome if a keystone predator is reintroduced to an ecosystem?

Accepted Answer

Consumer populations may decrease, and producer populations may recover

Core Study Topics for College Biology: Exam-Ready Guide

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