Population Ecology

Biology Ch 5-1& 5-2

Population Density The number of individuals per unit area Ex: 5 wolves in a 10 acre piece of land

Example: In an Ohio city, 1,400 rats lived in

an eight square block area. The city tore down the old buildings and replaced them with modern apartments. The new populations was160 rats.

a. Find the initial rat density.b. Find the new rat density.c. What is the change in the rat density?

Ducks vs. Fish

Populations of different species often have very different densities, even in the same environment.

A population of ducks in a pond may have a low density, while fish and other animals in the same pond community may have higher densities.

DistributionHow individuals in a population

are spaced out across the range of the population—randomly, uniformly, or mostly concentrated in clumps

Flowers Penguins Catfish

Growth Rate How a population changes

over time May stay the same, increase,

or decrease

EQ: Pop. @ end – Pop. @ startTime

Example:

Year Population2005 262006 382007 452008 722009 1052010 131

1. A biologist gathered the following data on a population of cliff swallows at Hudson Park, along 25 miles of the Fox River.

•What was the rate of change per year from 2005 to 2010?•What was the rate of change per year from 2006 to 2008?

•What was the density of the swallow population in 2009?

Population Growth

Changes in Population Density

Positive Population Change

Natality: birth rate Immigration:

entering

Negative Population Change

Mortality: death rate

Emigration: leaving

Example: A team of biologists studied a box turtle

population of 100 individuals in an Ohio woodlot for a period of 10 years. They determined natality to average 40 turtles per year. Mortality was 30 turtles per year. Immigration was 3 turtles per year. Emigration was 8 turtles per year.

 a. At what rate is the population changing?b. Is the population increasing or decreasing?c. If the initial population was 15 turtles, what was the population at the end of 10 years?