Population Ecology Presented By: Dean Thomas
What is population ecology? • A population is an assemblage of individuals of the SAME species inhabiting a given area. • Ecology is a field of biology that focuses on the interactions between organisms and their environment • So population ecology is the dynamics of a species population and how they interact with their environment
What kinds of things do population ecologists look at? • Population Structure • Population Growth
Population Structure • Interested in how many individuals make up the population. • How are the individuals distributed throughout the environment? • Age Structure
Types of Distribution • Clumped • Uniform • Random http://www.biology.iupui.edu/biocourses/n100/images/39dist.gif
Distribution? King Penguins on Salisbury Plain – Over 100,000 Penguins! http://www.vanda.eclipse.co.uk/travel/Antarctica/images/Chap_3/Part_3/SP_King_Penguins.jpg
Population Growth • Growth Rate = the percent change in a population over one year • Growth rate is affected by • ? • ? • ? • ?
Population Growth • Growth Rate = the percent change in a population over one year • Growth rate is affected by • Natality (births) • Mortality (deaths) • Immigration • Emigration
Growth rate = birth rate – death rate • Let’s try an example • A population of 100 rabbits gives birth to 30 rabbits in one year. • 30 births 100 adults = .30 * 100% = 30% birth rate • If 10 individuals of the 100 rabbits died, what is the death rate? • What is the growth rate of the rabbit population?
What’s going to happen if this continues? http://www.beltramiswcd.org/Aquatic%20Biology/Human%20Population%20Growth.jpg
If both of these species became endangered, which has a better chance of rebounding?
Can a population grow forever? • Animals have the capacity to grow exponentially, but they are limited by resources. • What are the four main resources that limit growth?
Can a population grow forever? • Animals have the capacity to grow exponentially, but they are limited by resources. • What are the four main resources that limit growth? • Food • Water • Shelter • Space
Carrying Capacity • The maximum population that can be supported by an environment Question: What would happen if a population grew beyond their carrying capacity? http://www.bio.miami.edu/dana/pix/logisticpopns.gif http://www.geo.arizona.edu/Antevs/nats104/00lect21grolog.gif
Carrying Capacity • Density-dependent factors
Carrying Capacity • Density-dependent factors • Population-limiting factors that increase as population increases in size • Food supplies • Risk of disease in crowded areas • Increase in toxin concentration caused by increased waste levels • Causes declines in birth or death rates
Carrying Capacity • Density-independent factors • Influences on population rates that are not affected by density • Severe drought • Cold winter • Effects could be worse depending on the size of population
Age Pyramids Which of the two pyramids show a more rapid growing population? What if (a) was inverted?
Let’s look at population ecology at work! Abby Benson - Abby is studying the population ecology and sex-biased dispersal of thirteen-lined ground squirrels in and out of prairie dog colonies in northern Colorado. Her research is also part of the broader NSF-funded plague project underway in northern Colorado. http://faculty.fullerton.edu/pstapp/IMG_3245.jpg
How do we estimate populations when we don’t have census data? • It’s hard to count every individual and can be very time consuming! • If the critters are mobile, they are probably sneaky and don’t want to be found. Makes your job a little harder.
Examples of population survey techniques • Plot sampling (Quadrat sampling) • Estimate density • Estimate percent cover • What types of organisms is this method good for? • What would it not work for? http://lh6.ggpht.com/_vgCJNdZcGw8/SGfKBHguBdI/AAAAAAAAAOg/yQIYwuH6g8c/SpellmanEcolab_Stephanie%26Me_plots.jpg
Examples of population survey techniques • Mark-Recapture Sampling • Capture • Mark all that you captured • Release • Recapture • Estimate population by the ratio of marked to unmarked
Examples of population survey techniques • Mark-Recapture Sampling • Equation: N/M = n/R • N = Estimated Population • M = Marked individuals • n = number of individuals in the second sample • R = Recaptured individuals • So, N = Mn/R
Examples of population survey techniques • Mark-Recapture Sampling • An example
Mark-Recapture Sampling in Action!Still Creek Fish Trap, Mt. Hood, OR Can you find the marked fish?
Mark-Recapture Sampling in Action!Still Creek Fish Trap, Mt. Hood, OR Back to the office to analyze the data!
Link to recent Hudson River plane crash http://www.cnn.com/2009/US/01/15/hudson.plane.videos/index.html
Where does population ecology come into play with the dangers of bird strikes?Well, lets be wildlife biologists and take a look!