⏳ Estimated Reading/Watching Time: 10 - 12 minutes

Calculate population growth rate.

Immigration vs. Emigration

Immigration is when organisms migrate to a new area, causing the population in the new area to increase, and emigration is when organisms migrate from an area, causing the source population size to decrease.

A way to remember which is which is the following: Immigration is when individuals are moving INTO a population. Emigration is when individuals are EXITING the population.

emigration and immigration using ducks. In the Emigration section, a duck flies away from the pond, while in the Immigration section, more ducks are in the pond, suggesting immigration. An arrow indicates movement from left to right, demonstrating how these processes impact population size and composition. — ***Immigration is when organisms migrate TO a new area and emigration is when organisms migrate FROM an area.***

The image illustrates population dynamics using ducks. Four groups symbolize births (yellow ducklings), immigration (white ducks), deaths (crossed-out duck), and emigration (white ducks). Arrows indicate how these factors influence population size, with a pond in the center representing the population. It simplifies the fundamental concepts of population dynamics. — ***Births and immigration to the area where a population lives cause a population to grow. Deaths and emigration away from the area where the population lives cause a population to shrink.***

If an individual moves from the United States to Germany, the population of the United States will decrease by 1 and the population of Germany will increase by 1. This individual emigrated from the United States and immigrated to Germany.

Emigration and immigration are important when we are trying to calculate population size (Note: if you are trying to calculate the global population, you do not need to consider emigration or immigration; you only need to consider births and deaths.)

If the births and immigration cancel out the deaths and emigration, the population size will remain steady.

Resource availability will also affect the population growth rate because an area with few resources will have a lower birth rate and higher death rate. If an area has few resources, individuals will emigrate away from the area to an area with more resources. If an area has abundant resources, individuals will immigrate to the area.

Births and immigration to the area cause populations to grow. Deaths and emigration away from the area cause populations to shrink. If the crude birth rate (CBR) and immigration cancel out the crude death rate (CDR) and emigration, the population size will remain steady.

Population Growth Rate Calculations

You can calculate the change in population size using the following formula:

LaTeX: (CBR+Immigration)–(CDR+Emigration)=PopulationGrowthRate

A positive growth rate means the population size is growing, a negative growth rate means the population size is decreasing, and a zero-growth rate means that the population size is stable.

Let's try our hand at calculating growth rates using the formula given above.

📈 Example 1 - Positive Growth Rate (click to reveal)

Watch the video below to learn how to calculate growth rate in a population whose growth rate is positive (the population size is increasing).

🟨 Example 2 - Steady Growth Rate (click to reveal)

Watch the video below to learn how to calculate growth rate in a population whose growth rate is zero (the population size is steady).

📉 Example 3 - Negative Growth Rate (click to reveal)

Watch the video below to learn how to calculate growth rate in a population whose growth rate is negative (the population size is shrinking).

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AP Exam Tip

With Immigration, individuals are moving INTO the population, increasing population size. With Emigration, individuals are EXITING the population, reducing the population size.

Memorize the population growth rate formula above. You cannot guarantee that it will be given to you on the AP exam.

You should know how to calculate growth rate and be able to interpret your answer.

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