Population Regulation: Density-Dependent vs. Density-Independent Factors

Biology Grades High School 10:32 Video
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Lesson Description

Explore the factors that regulate population growth, including density-dependent and density-independent factors. Learn about carrying capacity and how these factors influence population size.

Video Resource

Population regulation | Ecology | Khan Academy

Khan Academy

Duration: 10:32
Watch on YouTube

Key Concepts

  • Density-Dependent Regulation
  • Density-Independent Regulation
  • Carrying Capacity
  • Limiting Factors

Learning Objectives

  • Define and differentiate between density-dependent and density-independent factors regulating population growth.
  • Explain how density-dependent factors, such as competition, predation, disease, and waste accumulation, influence population size.
  • Describe how density-independent factors, such as natural disasters, can impact populations regardless of their density.
  • Understand the concept of carrying capacity and its relationship to population regulation.
  • Evaluate the factors influencing carrying capacity for human populations.

Educator Instructions

  • Introduction (5 mins)
    Begin by introducing the concept of population regulation and its importance in ecology. Briefly explain the two main categories: density-dependent and density-independent regulation. Show the video from Khan Academy (Population regulation | Ecology | Khan Academy).
  • Density-Dependent Factors (15 mins)
    Discuss density-dependent factors in detail. Use examples from the video, such as rabbit populations in Australia, to illustrate competition for resources (food, water, shelter, light). Explain how predation, disease, and waste accumulation become more significant as population density increases. Use real-world examples.
  • Density-Independent Factors (10 mins)
    Explain density-independent factors, emphasizing that their impact is not related to population density. Provide examples such as natural disasters (forest fires, floods, tsunamis) and their effects on populations. Discuss how these events can randomly reduce population size.
  • Carrying Capacity and Human Populations (10 mins)
    Define carrying capacity and its role in limiting population growth. Discuss the Malthusian limit and its relevance to human populations. Explore how technological advancements have allowed humans to push the carrying capacity, and discuss the philosophical question of whether there is an ultimate limit for human population growth.
  • Activity and Wrap-Up (10 mins)
    Lead students in the interactive exercise (see below). This could involve working in groups to discuss different limiting factors. End with a brief review of key concepts and assign the quizzes.

Interactive Exercises

  • Limiting Factors Scenario
    Divide the class into small groups. Assign each group a specific organism (e.g., deer, salmon, bacteria) and an environment (e.g., forest, river, petri dish). Have each group brainstorm a list of density-dependent and density-independent factors that could limit the population of their assigned organism in the given environment. Each group presents their findings to the class and discusses the relative importance of each factor.

Discussion Questions

  • How might climate change affect density-dependent and density-independent factors?
  • Can you think of examples of population regulation in your local environment?
  • How do human activities influence the carrying capacity of different ecosystems?
  • What are the ethical considerations of managing populations, especially in the context of endangered species or invasive species?

Skills Developed

  • Critical Thinking
  • Data Analysis
  • Problem-Solving
  • Communication

Multiple Choice Questions

Question 1:

Which of the following is a density-dependent factor that can regulate population growth?

Correct Answer: Competition for food

Question 2:

What term describes the maximum population size an environment can sustain?

Correct Answer: Carrying Capacity

Question 3:

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

Correct Answer: Flood

Question 4:

As a population reaches its carrying capacity, what happens to the birth and death rates?

Correct Answer: Birth rate decreases, death rate increases

Question 5:

Which of the following factors can spread more easily in dense populations?

Correct Answer: Disease

Question 6:

What happens to competition for resources as a population approaches its carrying capacity?

Correct Answer: Competition increases

Question 7:

Which scientist hypothesized about a limit to human population growth due to resource constraints?

Correct Answer: Thomas Malthus

Question 8:

What type of population growth pattern includes a carrying capacity?

Correct Answer: Logistic growth

Question 9:

What is waste accumulation considered as?

Correct Answer: Density-dependent factor

Question 10:

If predators have easier access to their lunch because there is a large dense population, what is that called?

Correct Answer: Predation

Fill in the Blank Questions

Question 1:

Regulation of populations that is dependent on the number of individuals in an area is called __________ regulation.

Correct Answer: density-dependent

Question 2:

The maximum population size that an environment can sustain is known as its __________.

Correct Answer: carrying capacity

Question 3:

__________ for resources, such as food and water, is a density-dependent limiting factor.

Correct Answer: Competition

Question 4:

Natural __________ are examples of density-independent factors that can affect population size.

Correct Answer: disasters

Question 5:

The spread of __________ and parasites is often easier in dense populations due to increased contact.

Correct Answer: disease

Question 6:

__________ accumulation can poison water and food sources, limiting population growth.

Correct Answer: Waste

Question 7:

__________ factors tend to be related to other living things around

Correct Answer: Biotic

Question 8:

__________ factors tend to be non-living.

Correct Answer: Abiotic

Question 9:

If you have a high density population and the waste is just everywhere, it could poison the ____

Correct Answer: water

Question 10:

The deer population may not be close to their carrying capacity, but the _________ can kill off a lot of the deer.

Correct Answer: forest fire

Educational Standards

B.LS2.1:Use mathematical and/or computational representations to support explanations of factors that affect carrying capacities of ecosystems at different scales. B.LS2.6:Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem. B.LS4.2:Construct an explanation based on evidence that biological diversity is influenced by (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment.

Teaching Materials

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