Factors that Lead to Population Change & Density

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• 0:02 Oil, Food, Water
• 0:37 Density Factors
• 1:38 Density-Dependent Factors
• 4:24 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
Can a population keep growing forever and ever? The answer is no. But do you know why that's the case? Here you'll learn the many factors at play in population changes stemming from population density.

Oil, Food, Water

Oil, food, water - what do they all have in common? They are all limited resources. We only have so much of each. What happens if we run out of enough oil, food and water in this world for all of its people? We will suffer massive consequences, all of which will result in population decline. Population change is governed by density-dependent and density-independent factors. This lesson's focus is on the different types of density-dependent factors related to population change.

Density Factors

But at first, let's have a quick look at what I mean when I say density-independent and density-dependent.

If a birth rate or death rate does not change with a population's density it is said to be density-independent. Similarly any factor that limits a population's size without depending on the population density is known as a density-independent factor. An example of this would be something like a volcanic eruption that kills off an entire city regardless of how sparsely or densely populated the city is.

The flipside to density independent factors are density-dependent factors, factors that limit a population's size based on the density of the population. Meaning, the birth rate, death rate or both, may change as a result of a change in the population's density. Let's take a look at many of the factors that are density-dependent.

Density-Dependent Factors

In the intro, I mentioned oil, food and water. What are these? These are resources. One factor that is density-dependent is competition for resources. For example, as a population of deer grows within a limited area, the amount of food the deer have to eat will decrease per individual deer, thereby reducing birth rates, increasing death rates or both.

Territoriality is a factor that is very similar to competition for resources because territory is itself a resource or at the minimum provides resources. If there isn't enough room to go around for everyone, then members of some species may become nonbreeding individuals within a population, thereby dropping birth rates. Or, members of a species may fight over space and increase death rates.

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