1. How Populations Grow
Ch 5.1

2. Population Density and Distribution
Population density: the number of individuals per unit area
Different species have different population densities
Population distribution: refers to how species are spaced out
Randomly
Uniformly
Clumped

3. Population Distributions
Random
Purple Lupines (flowers)
Uniform
King Penguins
Clumped
Striped Catfish

4. Factors Affecting Population Growth
Birth Rate / Death Rate
birth rate = death rate: population stays the same
high birth rate and low death rate: population increases
low birth rate and high death rate: population decreases
Immigration v. Emigration
immigration: species move into the range of the population
emigration: species move out of the range of the population

5. Exponential Growth
Under ideal conditions with unlimited resources, the population will continuously grow (exponential growth)
Exponential growth: the larger the population
gets the faster it grows

6. Logistic Growth
Logistic growth: when a population’s growth slows and then stops after exponential growth
The population has reached its
carrying capacity, or the
maximum number of species
an ecosystem can sustain