Analyzing Populations

Lesson 2

Analyzing Polulations

population density

• the number of organisms in a defined space

Factors affecting population growth patterns

• emigration-when an animal leaves a population

• immigration

• births

• deaths

Calculating Growth Rate

• equation takes into account the four factors that affect population size:

  r = (b + i) – (d + e)

  
  

r = (b + i) – (d + e)

• SOLVE 

  As part of a long-term elephant study, biologists counted individuals in a population of elephants each spring. In one year, there were 18 males and 34 females. Over the following year, each female gave birth, from which 28 offspring survived. Predators killed 9 elephants. A construction project cleared 50 acres of nearby forested land, causing 5 males and 19 females to immigrate into the study area. Competition for females increased, resulting in the emigration of 10 males to a new territory in search of mates.

  
  

  Find the growth rate of this population. 

disturbance

— a change in an ecosystem that impacts a population or a community

Exponential and Logistic Growth

• exponential growth-any species that lives in ideal conditions of available resources, space, and other factors will rapidly increase in population size. 

• logistic growth, a population begins with a period of slow growth followed by a period of exponential growth before leveling off to a stable size.

  
  

carrying capacity

- maximum population size of a species that a particular environment can normally and consistently support in terms of resources.

Population Dispersion

uniform random clumped

Factors That Limit Population Growth

Limiting Factors

• Density–dependent factors are factors that are affected by the number of individuals in an area. The larger the population, the greater the effect. 

• Density–independent factors are factors that can impact a population regardless of its density.