1. Characteristics of Populations
Chapter 19-Biology
Characteristics of Populations

2. 6 Characteristics of a Population
a. Geographic distribution or range: area inhabited by a population
i. Example: The “Philippine tarsier is endemic to the southern Philippine islands where it thrives mostly in secondary forests or dense patches or thickets of bush, tall grass, and bamboo

3. 6 Characteristics of a Population
b. Population density: measures how crowded a population is:
i. Number of individuals per unit of area or volume.
ii. Rank the following from most crowded to least crowded:
North America
South America
Europe
Asia
Australia
Africa

4. Population Density
1. Asia people per square mile
2. Europe people per square mile
3. South America - 73 people per square mile
4. Africa - 65 people per square mile
5. North America - 32 people per square mile
6. Australia people per square mile
iii. And Bangladesh has 2200 people per square mile!!

5. 6 Characteristics of a Population
c. Population Dispersion: Patterns of spacing in relationship to other members of the population:

6. 6 Characteristics of a Population
d. Population Growth rate
i. Three factors affecting population size:
1. # of births (birth rate)
2. # of deaths (mortality rate)
3. # of individuals leaving/entering
i. Immigration: into
ii. Emigration: exit

7. 6 Characteristics of a Population
d. Population Growth rate
ii. Exponential Growth
1. Individuals in a population reproduce at a constant rate
2. A.K.A. J-curve
3. Population growing at full biotic potential
The Scot’s Pine shows exponential growth

8. 6 Characteristics of a Population
4. Can populations grow forever?
-Microorganisms could grow exponentially for a long time if provided with food and space and if waste was removed.
-MOST populations are NOT exponential because resources become scarce and wastes accumulate.
-Any factor (like space) that restrains the growth of a population is a limiting factor

9. Can Populations Grow Forever
Can Populations Grow Forever? Draw a graph of exponential growth over time

10. 6 Characteristics of a Population
4. Population Growth rate
iii. Logistic Growth model
1. A.K.A. S-curve
2. Growth slows as the population reaches carrying capacity

11. e. Age Structure: the distribution of individuals among different ages in a population.

12. f. Patterns of Mortality: Survivorship curves show how death rates vary with age
1,000
Type I - high
mortality in old age
100
Number of
survivors
Type II - constant
mortality rates 10
Examples:
Type I - humans, many other large vertebrates, some plants and inverts
Type II - many birds, turtles
Type III - frogs, fish, many plants
Type III - high infant
or juvenile mortality 1
log10
scale
very
young
very
old
Age 12

13. Population Statistics
Video: Population Statistics
Video: The world in 2015 by “The Economist”