1. Identify the abiotic and biotic factors in this picture
Identify the abiotic and biotic factors in this picture. Make a list in your notebook.

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
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. 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 - Territorial
Clumped distribution: Organisms grouped near resources; most common distribution in nature

6. 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

7. Age Structure Diagram
Visual tool scientist use to show the age structure of populations
Show the number of males and females in different age groups within a population
Bottom heavy –capable of rapid growth
Even age- stable population
Top heavy- decline

8. 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.

9. What is the size of a population?
1. Number of individual in an entire ecosystem
2. How individuals in a population are spaced out
3. Number of individuals per unit area/volume
What is age structure?
1. Number of individuals in a population
2. Mean age the individuals are in a population
3. Number of males or females at a given age
Which of the following is an example of density?
1. 1 snake in a large field
2. 7 male and 6 female adult tigers in a jungle
3. 8 parrot fish and 75 silver fish in a lake

10. That’s CORRECT! Keep up the great work!
Next question

11. SORRY MAN, TRY AGAIN
SORRY MAN, TRY AGAIN