Population Density
What is population density?
How concentrated or close together individuals are within a given area.
It is calculated by dividing the total number of individuals in a population by the total area.
The answer is always individuals per unit of area
Which of the following best describes uniform dispersion?
a. Organisms clustered in groups
b. Organisms scattered randomly
c. Organisms evenly spaced
d. Organisms moving constantly
c. Organisms evenly spaced
What is the term for individuals physically entering a population?
a. Emigration
b. Immigration
c. Birth rate
d. Population flux
b. Immigration
In the equation r = (b + i) - (d + e), what does 'e' represent?
a. Environment
b. Evolution
c. Emigration
d. Elevation
c. Emigration
Population density is calculated by dividing the number of individuals by the total area they occupy.
True
➤ Population density = number of individuals ÷ area.
Interpret whether this population is very dense, or not dense: There are 2 chickens per square foot.
This is a dense population. It means you will see that there are two chickens every square foot, which is a very small space for two chickens.
What causes clumped dispersion in animal populations?
a. Competition for resources
b. Equal distribution of resources
c. Territorial behavior
d. Social behavior and safety in groups
d. Social behavior and safety in groups
In a predator-prey relationship, what typically happens to prey population when predator population increases?
a. Prey population increases
b. Prey population decreases
c. Prey population stays the same
d. Prey population becomes extinct
b. Prey population decreases
What does a negative growth rate indicate about a population?
a. The population is increasing
b. The population is decreasing
c. The population is stable
d. The population is migrating
b. The population is decreasing
Random dispersion means individuals are evenly spaced due to limited resources.
False
➤ Random dispersion occurs when individuals are spread unpredictably; uniform dispersion means evenly spaced.
If the population decreases, but the area stays the same, what happens to population density? (stays same, increases, or decreases)?
the population density decreases
Which dispersion pattern would you expect to see in territorial birds during nesting season?
a. Random
b. Clumped
c. Uniform
d. Variable
c. uniform
Which factor would most likely lead to emigration?
a. Abundant resources
b. Low population density
c. Resource competition
d. High birth rate
c. Resource competition
19. What does a population growth rate of zero indicate?
a. The population is extinct
b. The population is stable
c. The population is increasing
d. The population has no births or deaths
b. The population is stable
Births and immigration both contribute to a population’s decrease.
False
➤ Births and immigration increase population; deaths and emigration decrease it.
Which of these would cause population density to increase?
a. Larger habitat area
b. Higher death rate
c. Increased immigration
d. Increased emigration
c. Increased immigration
How do cacti typically disperse in their habitat?
a. Randomly
b. In clusters
c. Uniformly
d. In pairs
c. Uniformly
What are the four main factors that cause a population to change in size over time?
➤ Births, deaths, immigration, and emigration.
(These determine whether the population grows, declines, or stays stable.)
Which factor is NOT included in calculating population growth rate?
a. Births
b. Deaths
c. Population density
d. Immigration
c. Population density
Environmental changes, such as wildfires or habitat loss, can lead to negative population growth.
True
➤ Environmental changes like fires or habitat destruction can reduce population growth (negative growth rate).
If you have 500 rabbits in 20 square kilometers, what would be the population density?
Divide 500 rabbits by 20 square kilometers. You get 25 rabbits per square kilometers
Why do organisms engage in uniform dispersion?
Resource competition
Explain how immigration and emigration affect population size. (Hint: think of decreases and increases in size)
➤ Immigration (organisms entering an area) increases population size.
Emigration (organisms leaving an area) decreases population size.
If the immigration rate=5, deaths=10, and births=20, what is the population growth rate?
r=(b+i)-(d+e)
(20+5)-(10+0)
25-10
=15
Population density and dispersion can help scientists monitor the health of a species or habitat.
True
➤ Scientists use density and dispersion to assess ecosystem health and population stability.
What are the units when you calculate population density?
Hint: _______ per ________
individuals per unit squared
What is the primary reason for wolves displaying clumped dispersion?
Social hunting behavior
How does the availability of resources influence birth and death rates in a population?
➤ When resources are plentiful, birth rates tend to rise and death rates drop.
When resources are scarce, birth rates fall and death rates increase.
What does a population growth of -15 mean?
It means that the population is decreasing at a rate of -15 per year (or other unit of time if indicated).