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When you come to the end of your rope, tie a knot and hang on. ~Franklin D. Roosevelt
Exit Card
1. Name 3 general models that are used to estimate a population’s size.
2. How do element cycles (carbon, nitrogen, phosphorus, etc.) affect a population size
3. Should humans intervene with at-risk populations that have not been disturbed by humans?explain.
density of population
• measurement of population per unit area or unit volume.
Stable density population
• How many of the five million eggs that a female cod might lay over the course of her life will, on average, survive and grow to adulthood?
Who leaves more offspring a pair of elephants or a pair of rabbits?
Changing population density
Exponential Growth Model
• Generation and generation – more offspring produced than parents. OR Immigration of species is occurring.
• J-shaped curve-
• “You decide to invest $1000 in a savings account. Your investment will grow at a rate of 10% each year. Assuming that you reinvest the interest each year, how much money will you have in 30 years?”
Doubling Time and the Rule of 70
• Calculating the time it will take for a population (or money) to double.
• Exponential growth at a constant rate only• Divide 70 by the percentage growth rate.
If the population of rabbits in an ecosystem grows at a rate of
approximately 4 percent per year, the number of years required for the rabbit
population to double is closest to
a. 4 years b. 8 years c. 12 years d. 17 years e. 25 years Solution: 70/4 = 17.5 years, the closest answer to 17.5 would be “d” 17 years.
Logistic Growth Model• Logistic growth- when a population whose growth is
initially exponential, but slows as the population approaches the carrying capacity.
• S-shaped curve- when graphed the logistic growth model produces an “S”.
What influences carrying capacity?Density Dependent factors : (pop density is affected because of its size)• Food supply • Habitat for living and breeding• Parasitism• Predation risk
Extreme Animal Myth
• Do Lemmings take density depended factors too far? And go into madness?
What influences carrying capacity?
• Density Independent Factors: (pop density is affected regardless of its size)
• Natural disasters (floods earthquakes, fires• Human hunting• Changes in chemicals present•
Management1. What type of growth model is the
elephant population illustrating?2. Explain two concerns with this and
its likely outcome if continued 3. What is the reproductive strategy of
the elephant (r-selected or k-selected?(explain your answer)
4. Draw a survivorship curve that best exhibits that best exhibits the elephants lifetime survivorship.
5. Create a plan to stabilize the population of the elephants.
Management1. What type of growth model is the elephant
population illustrating?Exponential Growth Model2. Explain two concerns with this and its likely outcome if continuedDisease or starvation = concernsLikely outcome is a population crash3. What is the reproductive strategy of the elephant (r-selected or k-selected?(explain your answer)K-selected4. Draw a survivorship curve that best exhibits that best exhibits the elephants lifetime survivorship.5. Create a plan to stabilize the population of the elephants.
K Stable environment, density dependent interactionslarge size of organismenergy used to make each individual is highfew offspring are producedlate maturity, often after a prolonged period of parental carelong life expectancyindividuals can reproduce more than once in their lifetimetype I or II survivorship patternin which most individuals live to near the maximum life span
Predator Prey Relationship
