Population DynamicsStudying Populations

Changes in CommunitiesSEV3. 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?

What to Do!

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Copy Every Question & Answer

Studying Populations

I. How Can You Determine Population Size?

A. Direct Observation1. Most obvious way2. Count all members

B. Indirect Observation1. Observe signs of organisms2. Use simple math

C. Sampling1. Estimate size of small area

to figure out larger area2. Estimate – an

approximation of a # bases on reasonable assumption

D. Mark-and-Recapture3. Count & mark specimen4. Release then recapture5. Count & estimate

II. What Causes Changes in Population Size

A. Births and Deaths1. Birth rate - # of births in a

population2. Death rate - # of deaths in

a population

• What 2 Population Statements Can We Make?

1. If birth rate > death rate, pop. size increases

2. If death rate > birth rate, pop. size decreases

B. Immigration and Emigration1. Immigration (“in”) – moving into a

population2. Emigration (“exit”) – leaving a

population

• How Can You Graph Changes in Populations?1. Display on line graph2. Vertical Axis - # of organisms3. Horizontal Axis - time

• What is Population Density?1. The number of individuals in an area of a specific size2. EquationPopulation Density = Number of individuals Unit Area

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)

A. Food and WaterB. SpaceC. WeatherCarrying Capacity (K) is the largest population size an area can support.

What are 2 Categories of Limiting Factors?

Density- Dependent

1. Only become limiting when a population reaches a certain size

2. Factors include: competition, disease, predation

Density-Independent

1. Limiting no matter the size of the population

2. Factors include: weather, natural disasters, seasonal cycles

What are 2 Types of Growth?1. Exponential Growth

(J-shaped curve) – occurs when population growth starts slow then increases rapidly

2. Logistic Growth (S-shaped curve) - occurs when population growth reaches its carrying capacity due to limiting factors and levels off

Changes in Communities

I. What is Succession and what does Primary Succession Involve?

1. Succession refers to the series of predictable changes that occur in a community over time

2. Primary Succession – series of changes that occur in an area where no soil or organism exits. Ex. Newly formed island

3. Pioneer Species – 1st species to populate the area. Ex. Mosses & Lichens

II. What does Secondary SuccessionInvolve?

1. Secondary Succession – series of changes that occur in an area where the ecosystem has been disturbed, but soil and organisms still exist

2. Factors affecting this succession can be humans, or small forces in nature (forest fires, tornadoes, hurricanes, & floods)

3. Occurs more rapidly that primary succession.

Graph 1: Rabbits Over Timea. The graph shows a __________ growth curve.b. The carrying capacity for rabbits is __________c. During which month were the rabbits in exponential growth? ____________

LET’S PRACTICE!For the following slides,use Graphs (1,2,&3)to answer the questions

Graph 2: Average Toe Lengtha. In 1800, about how many people surveyed had a 3 cm toe? _________b. How many in 2000? ___________c. The data shows the ____________ selection has occurred?d. In 2000, what is the average toe length? __________e. What is the average toe length in 1800 ___________

LET’S PRACTICE!

Graph 3: Mexico and USa. In Mexico, what percentage of the population is between 0-4 years of age? ______b. In the US, what percentage of the population is between 0-4 years of age? ______c. Which population is growing the fastest? ________d. Which age group has the smallest number in both countries? ________

LET’S PRACTICE!