1. Bell Ringer
You need:
Both handouts
Calculator

2. 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.

3. 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

4. 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

5. 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

6. Why Measure/Track Populations?
Tracking Snakes in the Wild: Mark Recapture Techniques

7. 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?

8. 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.

9. 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

10. Population Distribution
Lesson 4.2 Describing Populations
Population Distribution

11. 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

12. 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

13. 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

14. 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.

15. 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