1 00ECOLOGYBIO 1 INTRO Population Limiting Factors Density

1. 00_ECOLOGY_BIO 1 INTRO Population Limiting Factors (Density Independent) Slides 143 -151

Density-Independent Limiting Factors

Population Ecology: Density-independent factors Population Limiting Factors • Density-independent factors – Factors that limit population size, regardless of population density. – These are usually abiotic factors – They include natural phenomena, such as weather events • Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc.

Density-Independent Factors Density-independent limiting factors affect all populations regardless of population size and density.

Density-independent limiting factors limit a population’s growth regardless of the density. a. unusual weather b. natural disasters c. human activities

Density-Independent Factors Examples: hurricanes, droughts, floods, wildfires Density-independent factors may actually vary with population density. Canyon Lake, TX

Chapter 5 Part 4 - Density-Independent Limiting Factors https: //www. youtube. com/watch? v=9 SBmm 2 Iz. Ccw

KEY FEATURES OF POPULATIONS Population size is limited by: Density-dependent factors • • • Disease Competition Predators Parasites Food Crowding – The greater the population, the greater effect these factors have. – Ex. Black plague in the Middle Ages – more deaths in cities Density-independent factors – – – – Volcanic eruptions Temperature Storms Floods Drought Chemical pesticides Major habitat disruption (as in the New Orleans flooding) • Most are abiotic factors

Controlling Invasive Species Density-independent measures? • Herbicides, mechanical removal Density-dependent measures? • Predation Salvinia Expensive, temporary Another invasive species?

Overview: Limits to Growth Flood waters cover a field of wildflowers. Non-native snakes released into a wetland prey on native rodents. Flu virus spreads quickly in schools. Wildfires spread through a grassland. Density dependent Density independent