Population Dynamics: Studying Populations Changes in Communities Unit 1: Ecology SB4: Assess the dependence of all organisms on one another and the flow of energy and matter within their ecosystems. Element c: Relate environmental conditions to successional changes in ecosystems Element d: Assess and explain how human activities influence the environment 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! When ever you see this symbol Be prepared to write. Copy Every Question & Answer

Studying Populations

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

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

What is Population Density? The number of individuals in an area of a specific size Equation Population 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) Food and Water Space Weather Carrying Capacity (K) is the largest population size an area can support.

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

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

Changes in Communities

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 exists. Ex. Newly formed island Pioneer Species – 1st species to populate the area. Ex. Mosses & Lichens

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.

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? ____________

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 ___________

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? ________

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