Environmental Science / Unit 4: Populations
4.1 Population Characteristics
Notes
A population is a group of the same species living in one area. Ecologists describe populations by size, density, distribution, and age structure.
- Population density is individuals per unit area: $\displaystyle \text{density} = \frac{\text{number of individuals}}{\text{area}}$.
- Distribution patterns: clumped (groups, most common, near resources), uniform (evenly spaced, often from competition), and random (unpredictable).
- Population size changes through births, deaths, immigration (moving in), and emigration (moving out).
- Example: 450 deer live in 30 km$^2$ of forest, so density $= 450 \div 30 = 15$ deer per km$^2$.
Practice
A park has 600 squirrels living in 40 square kilometers. What is the population density?
$600 \div 40 = 15$ squirrels per square kilometer.
Penguins nesting in tight groups on an ice shelf show which distribution pattern?
Individuals gathered in groups show a clumped pattern.
Which of these increases the size of a population?
Births and immigration add individuals.
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