Lesson 23: Introduction - Populations

 

What happens in our world when the population expands? In 1900, there were about two billion people living on the planet. That number has more than tripled in 100 years. Today, more than seven billion live on the earth!

That number raises some questions: Will we continue to have enough resources to feed ourselves? What happens to the environment? Where do we all live? Can everyone be employed?

In this lesson, you will begin thinking about these kinds of questions. First, however, you will look at factors that affect the size of populations, including what can limit a population.

 

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Key terms for this lesson:

• population
• birth rate
• death rate
• immigration
• emigration
• abiotic limiting factors
• biotic limiting factors
• competition
• predation
• parasitism