1. Population Dynamics Studying Populations Changes in Communities
SEV3. Students will describe stability and change in ecosystems.
a. Describe interconnections between abiotic and biotic factors, including normal cyclic fluctuations and changes associated with climatic change (i.e. ice ages).
b. Explain succession in terms of changes in communities through time to include changes in biomass, diversity, and complexity.
c. Explain how succession may be altered by traumatic events.
d. Explain how biotic and abiotic factors influence populations.
Essential Question (s):
1). What are the costs and benefits of building a Wal-Mart closer
to a residential area?
2). What would happen to the schools’ baseball field if left
undisturbed?

2. What to Do!
When ever you see this symbol Be prepared to write. Copy Every Question & Answer

3. Studying Populations

4. I. How Can You Determine Population Size?
Direct Observation
Most obvious way
Count all members
Indirect Observation
Observe signs of organisms
Use simple math
Sampling
Estimate size of small area to figure out larger area
Estimate – an approximation of a # bases on reasonable assumption
D. Mark-and-Recapture
Count & mark specimen
Release then recapture
Count & estimate

5. II. What Causes Changes in Population Size
Births and Deaths
Birth rate - # of births in a population
Death rate - # of deaths in a population
What 2 Population Statements Can We Make?
If birth rate > death rate, pop. size increases
If death rate > birth rate, pop. size decreases
B. Immigration and Emigration
Immigration (“in”) – moving into a population
Emigration (“exit”) – leaving a population
How Can You Graph Changes
in Populations?
Display on line graph
Vertical Axis - # of organisms
Horizontal Axis - time

6. What is Population Density?
The number of individuals in an area of a specific size
Equation
Population Density = Number of individuals
Unit Area

7. III. What is a Limiting Factor? Carrying Capacity?
A limiting factor is any environmental agent that causes the population to decrease. It limits growth.
(Provide examples of how each type of limiting factor below may affect a population)
Food and Water
Space
Weather
Carrying Capacity (K) is the largest population size an area can support.

8. What are 2 Categories of Limiting Factors?
Density- Dependent
Density-Independent
Only become limiting when a population reaches a certain size
Factors include: competition, disease, predation
Limiting no matter the size of the population
Factors include: weather, natural disasters, seasonal cycles

9. What are 2 Types of Growth?
Exponential Growth (J-shaped curve) – occurs when population growth starts slow then increases rapidly
Logistic Growth (S-shaped curve) - occurs when population growth reaches its carrying capacity due to limiting factors and levels off

10. Changes in Communities

11. I. What is Succession and what does Primary Succession Involve?
Succession refers to the series of predictable changes that occur in a community over time
Primary Succession – series of changes that occur in an area where no soil or organism exits. Ex. Newly formed island
Pioneer Species – 1st species to populate the area. Ex. Mosses & Lichens

12. II. What does Secondary Succession Involve?
Secondary Succession – series of changes that occur in an area where the ecosystem has been disturbed, but soil and organisms still exist
Factors affecting this succession can be humans, or small forces in nature (forest fires, tornadoes, hurricanes, & floods)
Occurs more rapidly that primary succession.

13. LET’S PRACTICE! For the following slides, use Graphs (1,2,&3)
to answer the questions
Graph 1: Rabbits Over Time
a. The graph shows a __________ growth curve. b. The carrying capacity for rabbits is __________ c. During which month were the rabbits in exponential growth? ____________

14. LET’S PRACTICE! Graph 2: Average Toe Length
In 1800, about how many people surveyed had a 3 cm toe? _________
How many in 2000? ___________
The data shows the ____________ selection has occurred?
In 2000, what is the average toe length? __________
What is the average toe length in 1800 ___________

15. LET’S PRACTICE! Graph 3: Mexico and US
In Mexico, what percentage of the population is between 0-4 years of age? ______
In the US, what percentage of the population is between 0-4 years of age? ______
Which population is growing the fastest? ________
Which age group has the smallest number in both countries? ________