1) Populations have properties of size, density, and dispersion. Population size can be estimated through sampling if too large to count directly. 2) Population density expresses the number of individuals per unit area or volume. Some areas are densely populated while others are sparsely populated. 3) Dispersion describes how individuals are distributed within an area, which can be clumped, even, or random.

1. Chapter 20 Populations Note-taking Guide
3 Properties of Populations
1.
2.
3.
Population Size
Population-
Population size-
Sometimes there are too many to count so a ______________________is used.
Scientists count a __________________________________ in a certain area and
____________________ the area.
Population Density
Population density-
The number is always expressed as the number of _________________ per unit of
____________ or ___________________
Some areas are _____________ populated and others are _______________ populated

2. Population Dispersion
Dispersion is the ____________________ distribution of individuals within a
__________________.
There are three types of dispersion.
Clumped dispersion
Even dispersion is the result of
Random dispersion results from
Population Dynamics
All populations are ___________________, meaning they ________________ in
________________ and __________________ over ___________________.
Birth rate-
Death rate (mortality rate)-
Life expectancy-

3. Age Structure
Age structure-
Different countries have different age structures.
We can use graphs to compare age structure.
1. Which country shows the most potential for rapid growth? How do you know?
2. Which country has the least amount middle aged people (ages 40-50)?

4. 3. Which country has the youngest individuals (ages 0-9)?
4. Which country would see a decline in growth rate?
5. What does the future look like for each of these countries based on population and
age structures? Be specific about population.
Survivorship Curves
The mortality rate data of different species tend to conform to one of three curves on a
graph.
Type I organisms are more likely
Type II organisms have a linear look
Type III organisms are more likely to
Population Growth Rate
Growth rate-
Immigration-
Emigration-

5. Exponential Growth Model
Exponential Model-
Limiting factor-
Limiting factors are
Logistic Growth Model
Logistic model-
Carry capacity-
Once carrying capacity is reached….
Population Regulation

6. Density-independent factors-
Density-dependent factors-
Perils of small populations
The _________________ human population has caused extreme reductions in the
populations of some other _____________________________________.
Fewer than ____________________________________ remain in the wild due to over
___________________________________________________________.
The California condor is down to __________________________.
Fewer individuals mean ________________________________________________.
This means the babies will be more likely to have
___________________________________.
Essential Questions
•Explain how two populations can be the same size but have different densities.
•Explain why even distributions usually result from social interactions between
individuals.

7. •Explain why natural selection might favor a high reproduction rate in organisms with a
type III survivorship curve.
•Explain what is described by the exponential model.
•List two density-independent factors.
•Explain how inbreeding can threaten the survival of a small population.