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Lesson 4.2 Describing Populations From 1900 to 2000, the white-tailed deer population of New York state grew from about 20,000 to more than 1 million. Densities of more than 100 deer per sq mi occur in some metropolitan areas.

Lesson 4.2 Describing Populations Population Size The number of individuals in a population at a given time Population: individuals of the same species living in a particular place at the same time Sudden and dramatic decreases in population size can indicate an unhealthy population headed toward extinction. Ecologists often use sampling techniques to estimate population size. Did You Know? The passenger pigeon was once North America’s most abundant bird. Hunting drove them to extinction in less than 100 years. Counting Laysan Albatross Nests

Population Density Measure of how crowded a population is Lesson 4.2 Describing Populations Population Density Measure of how crowded a population is Larger organisms generally have lower population densities. Low population density: More space, resources; finding mates can be difficult High population density: Finding mates is easier; tends to be more competition; more infectious disease; more vulnerability to predators Northern pintail ducks

Ways to Measure Population Density Counting individuals within boundaries Estimation by random sampling Indirect indicators Mark-recapture method Place traps in population boundaries Mark captured animals (M) Mix marked animals back into population Set traps to recapture animals Compare # of marked (m) to total recaptured (n) N = (M x n) / m

Why Measure/Track Populations? Tracking Snakes in the Wild: Mark Recapture Techniques http://www.youtube.com/watch?v=5DR50IgvE7g

Bell Ringer Turn in post-test Pick up today’s activity and a calculator (2 per table) Using your notes that we started Monday, answer the following questions: What does population density measure? What are 4 methods of measuring population density?

Bell Ringer Pick up a calculator if you need to finish calculations QOD Using your notes that we started Monday, answer the following question: Compare and contrast the benefits and problems of low population density v. high population density.

When you finish your Mark-Recapture Activity: Place it on the front table Grab a sheet of notebook paper for you and your partner Divide paper in 2 (everyone needs a half sheet) Pull out your Ch. 4.2 Describing Populations note packet

Population Distribution Lesson 4.2 Describing Populations Population Distribution http://www.youtube.com/watch?v=BMsmDy-2jbA

Population Distribution Lesson 4.2 Describing Populations Population Distribution How organisms are arranged within an area: Random distribution: Organisms arranged in no particular pattern Uniform distribution: Organisms evenly spaced Clumped distribution: Organisms grouped near resources; most common distribution in nature

Population Abundance Abundance is a function of two factors: Lesson 4.2 Describing Populations Population Abundance Abundance is a function of two factors: Population density Population distribution Relative abundance map for the Scarlet Tanager. Retrieved from http://www.mbr-pwrc.usgs.gov/bbs/genintro.html

Lesson 4.2 Describing Populations Age Structure Relative number of organisms of each age group within population Can be used to predict future population growth of a population

Sex Ratios Proportion of males to females Lesson 4.2 Describing Populations Sex Ratios Proportion of males to females Age structure diagrams give information about sex ratios. For a monogamous species, the ideal sex ratio is 50:50.

Lesson 4.2 Describing Populations QOD Quiz Number your half sheet of paper 1-4, then label each diagram using one of the listed descriptions. You can use your notes. 1 2 3 4 Descriptions: Rapid growth Zero growth Negative growth (declining) Slow growth