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Science

PRACTICE WORKSHEET

Limiting Factors & Population Dynamics

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📋 Instructions

  • This practice test contains 23 multiple-choice questions and 1 extended-response question.
  • Read each passage and data table carefully before answering.
  • Select the best answer for each multiple-choice question. There is only one correct answer per question.
  • For the extended response, write clearly and support your ideas with specific evidence from the passages and the data table.
  • You may use a scientific calculator (such as the TI-30XS) for any calculations.
  • Recommended time: 45–55 minutes.
Remember: Take your time and think like a scientist. Base your answers on evidence from the text and data.

SCIENCE TEST FOCUS

This worksheet emphasizes data interpretation, experimental design (variables, controls), and scientific reasoning about populations and ecosystems. Use evidence from both the passage and the data table in your answers.

PASSAGE 1 Limiting Factors and Carrying Capacity

In any ecosystem, populations of organisms do not grow indefinitely. The maximum number of individuals of a species that an environment can support over time is called the carrying capacity. Several factors limit population growth. These are called limiting factors.

Limiting factors can be density-dependent (their effect increases as population density increases) or density-independent (their effect is unrelated to population density). Examples of density-dependent factors include competition for food or space, predation, and disease. Density-independent factors include natural disasters, extreme weather, and human activities such as habitat destruction or pollution. When a population exceeds its carrying capacity, limiting factors usually cause the population to decline until it returns to a sustainable level.

1

What is the main idea of Passage 1?

2

According to the passage, which of the following is an example of a density-dependent limiting factor?

3

If a deer population greatly exceeds the carrying capacity of its habitat, what is the most likely long-term outcome according to the passage?

4

Which statement best describes the relationship between carrying capacity and limiting factors?

5

According to the passage, which of the following human activities would most likely act as a density-independent limiting factor for a wildlife population?

PASSAGE 2 / EXPERIMENT Investigating Limiting Factors on Fish Population in a Pond

Scientists studied a small pond to understand what limits the population of a certain species of fish. They set up four large experimental tanks with similar conditions to the pond. Each tank started with the same number of fish. Over 12 weeks, they recorded the average number of fish surviving in each tank under different conditions.

Table 1. Average Number of Fish Surviving After 12 Weeks Under Different Conditions
Tank Food Availability Predators Present Avg. Fish at Week 12
Tank 1 (Control)HighNo48
Tank 2LowNo19
Tank 3HighYes27
Tank 4LowYes9

Note: All tanks started with 50 fish. Temperature, water quality, and space were kept the same in all tanks.

6

In this experiment, what is the dependent variable?

7

Which tank serves as the control group?

8

Based on the data in Table 1, which limiting factor appears to have the strongest negative effect on fish survival when acting alone?

9

Which statement is best supported by comparing Tank 1 and Tank 4?

10

The data suggest that low food availability and the presence of predators have which type of combined effect?

11

If the scientists wanted to test whether disease is also a limiting factor, what would be the best improvement to the experiment?

12

Based on the data, which condition would most likely allow a fish population to reach or exceed carrying capacity in a natural pond?

ADDITIONAL QUESTIONS
13

Which of the following is the best example of a density-independent limiting factor?

14

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

15

A scientist is studying how temperature affects the growth rate of bacteria. She sets up three identical cultures at different temperatures while keeping everything else the same. What is the independent variable?

16

Which of the following would most likely increase the carrying capacity of an ecosystem for a herbivore population?

17

In an experiment, a researcher notices that results vary widely between trials even though conditions seem the same. What should the researcher do first?

18

Which of the following best explains why only a small amount of energy is transferred from one trophic level to the next in a food chain?

19

A biologist wants to test the effect of different amounts of fertilizer on plant growth. She sets up four groups of plants and gives each group a different amount of fertilizer while keeping light, water, and soil type the same. What is the dependent variable?

20

Which of the following human activities would most likely decrease the carrying capacity of an area for native wildlife?

21

In a well-designed experiment, why is it important to change only one variable at a time?

22

Which of the following is an example of a density-dependent limiting factor that can affect human populations?

23

According to scientific understanding, which statement about carrying capacity is most accurate?

EXTENDED RESPONSE

Extended Response Question

Prompt: Using specific evidence from Passage 1 and the data in Table 1, explain how limiting factors can affect population size. Then, describe one realistic way humans could manage an ecosystem to help maintain a stable wildlife population. Support your answer with evidence from the test materials.

Write your response below (aim for 5–8 clear sentences):
Reflection & Self-Assessment

How confident do you feel about your performance?

Which skill do you want to review most?

One strategy that helped me (or one I will try next time):

FOR INSTRUCTORS ONLY — DO NOT DISTRIBUTE TO STUDENTS

Quick Answer Key

1. A
2. B
3. D
4. A
5. B
6. C
7. C
8. D
9. A
10. C
11. A
12. B
13. D
14. B
15. C
16. D
17. B
18. C
19. A
20. D
21. B
22. C
23. A

Answer distribution: A=6, B=6, C=6, D=5 (balanced and different from previous tests).

Detailed Answer Explanations

Question 1 — Correct Answer: A

Option A correctly summarizes the main idea: populations are limited by carrying capacity and both types of limiting factors. The other options are either too narrow or incorrect.

Question 2 — Correct Answer: B

Competition for food is a classic density-dependent factor — its impact grows as population density increases. Options A, C, and D are density-independent.

Question 3 — Correct Answer: D

When a population exceeds carrying capacity, limiting factors cause it to decline until it returns to a sustainable level. Option D correctly reflects this outcome described in the passage.

Question 4 — Correct Answer: A

Carrying capacity is determined by the combined effects of limiting factors in the environment. This is directly supported by the passage.

Question 5 — Correct Answer: B

Large-scale deforestation affects habitat regardless of current population size, making it density-independent. The other options are density-dependent.

Question 6 — Correct Answer: C

The dependent variable is what was measured as the result of the experiment: the average number of fish surviving after 12 weeks.

Question 7 — Correct Answer: C

Tank 1 is labeled as the Control and has high food with no predators — the baseline condition.

Question 8 — Correct Answer: D

Low food availability caused the largest single drop in survival when comparing Tank 1 to Tank 2. This makes low food the strongest single limiting factor in this data set.

Question 9 — Correct Answer: A

Tank 4 (low food + predators) had only 9 fish surviving — much lower than either factor alone. This supports a combined negative effect.

Question 10 — Correct Answer: C

Tank 4 had the lowest survival. The data shows that low food combined with predators produced a stronger negative effect than either factor by itself.

Question 11 — Correct Answer: A

Adding a tank with disease while keeping other conditions like Tank 1 would allow the scientists to test disease as an additional limiting factor in a controlled way.

Question 12 — Correct Answer: B

High food and few predators (similar to Tank 1) produced the highest survival. This condition would most likely allow a population to reach or maintain carrying capacity.

Question 13 — Correct Answer: D

A forest fire affects habitat regardless of population size, which is the definition of a density-independent limiting factor.

Question 14 — Correct Answer: B

In most ecosystems, only about 10% of the energy stored at one trophic level is transferred to the next. The rest is lost as heat through metabolism.

Question 15 — Correct Answer: C

The independent variable is the factor the scientist changed on purpose: the temperature of each culture.

Question 16 — Correct Answer: D

Increasing the amount of available plant food would directly increase the carrying capacity for herbivores.

Question 17 — Correct Answer: B

When results are inconsistent, the first step should be to check for errors in procedure or measurement and repeat the trials to improve reliability.

Question 18 — Correct Answer: C

Most of the energy at each trophic level is used for metabolism and lost as heat. Only a small percentage (about 10%) is transferred to the next level.

Question 19 — Correct Answer: A

The dependent variable is what is measured in response to the independent variable. In this case, plant growth (height or mass) is being measured.

Question 20 — Correct Answer: D

Large-scale removal of native vegetation destroys habitat and food sources, directly decreasing the carrying capacity for native wildlife.

Question 21 — Correct Answer: B

Changing only one variable at a time allows the researcher to clearly determine which factor is responsible for any observed changes in results.

Question 22 — Correct Answer: C

The rapid spread of an infectious disease in a crowded city becomes worse as population density increases, which defines a density-dependent limiting factor.

Question 23 — Correct Answer: A

Carrying capacity can change over time if environmental conditions (food supply, habitat quality, climate, etc.) change. This is a key concept from the passage.

Mentor Guide
Practical Guidance for Instructors & Tutors

✓ Effective Grading & Feedback

  • • Begin feedback with genuine praise for what the student did well.
  • • Use simple rubrics focused on 2–3 key skills: identifying limiting factors, interpreting data tables, and using evidence from text + data.
  • • Give credit for strong reasoning even if the final answer choice is incorrect.
  • • Provide specific, actionable comments and allow flexible response formats when writing is difficult.
  • • Focus on growth by comparing current work to the student’s own previous efforts.

📚 Teaching Concepts Students May Have Missed

Limiting Factors vs. Carrying Capacity: Use simple visuals (T-chart or diagram) to show that carrying capacity is the result of limiting factors. Connect to real examples like deer overpopulation or fish in a pond.

Density-Dependent vs. Density-Independent: Teach students to ask: “Does the effect get stronger when there are more individuals?” Practice with examples from the test.

Interpreting Data Tables: Practice comparing rows while holding one variable constant. Highlight key numbers and look for trends.

Experimental Design: Reinforce the three key questions: What was changed on purpose? What was measured? What was kept the same?

Multi-sensory approaches: Draw population graphs, act out “predator vs. prey,” or use sentence starters for the extended response.

💡 General Tips for Mentors

  • • Be patient and encouraging. Celebrate small successes.
  • • Adapt materials when needed (larger font, highlighters, oral responses).
  • • Build self-advocacy and make learning relevant to students’ daily lives and goals.
  • • Review key ideas frequently and create a supportive environment.
Every adult learner brings valuable life experience. Help them connect that experience to scientific concepts and build confidence as capable thinkers.
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