Chapter 46 - Population Ecology

Introduction to Ecology

• ecology 

• levels of study

  • population 

  • community

  • ecosystem

Characteristics of Populations

• size

• age structure

• density

• distribution

Population Growth

• 3 factors influence how a population will change in size: 1) births; 2) deaths; 3) migration

• change in pop. size = (births-deaths) + (immigrants-emigrants)

• ultimate size of a population is a balance between:

  1. biotic potential

  2. limiting factors

• growth based solely on the biotic potential is exponential

  • pop. growth = growth rate X original pop. size

• exponential growth cannot be maintained

• effects of limiting factors stabilizes growth

  • pop. size maintained at or below carrying capacity

  • density-independent factors (e.g. weather)

  • density-dependent factors (e.g. competition)

Human Population Growth

• it is growing exponentially

• we have been able to increase Earth's carrying capacity

• such growth cannot be maintained

• pop. stability is maintained when replacement-level fertility is reached
• age structures can be used to predict future population growth

Patterns of Survival and Reproduction

• reproductive success
• species vary in the time and energy devoted to different activities
• survivorship curves

© Carol L. Wymer, 2004