Population Growth KEY TERMS J curves S curves
- Slides: 13
Population Growth KEY TERMS: J curves S curves Exponential vs Logistic Carrying capacity, k Intrinsic growth rate, r Growth rate Doubling time Rule of 70 Age structure diagrams
Which would you rather have? �Would you rather be paid $100 a day for a month or 1 dollar the first day, 2 dollars the second day, 4 dollars the next day, 8 dollars the next day…etc. for the rest of the month?
Exponential Growth – with bank accounts �Bank accounts have an interest rate - causes your account to grow. �Interest rate is like the intrinsic rate of growth, r The larger r is, the faster the population will grow.
What’s the difference between these types of population growth? 5
J-curve vs. S-curve
When might you see exponential growth? �When a population isn’t limited by resources �Happens earlier in development of a population. �As long as the growth rate, r, is not 0, will see this type of growth
How can you reconcile these two graphs? Growth rate decreasing Population Size increasing
Growth rate: births, deaths, immigration, emmigration Make pops bigger Make pops smaller �Births �Deaths �Immigration �Emigration
How long does it take a population to double? �If you know the growth rate, you can calculate doubling time. �If you know the doubling time, you can calculate growth rate Rule of 70: Doubling time = 70/r (don’t convert percent to decimal)
Your turn! 1. Calculate the doubling time for the following population: time (years) population size 0 100 5 120 10 145 15 170 20 200 2. Use the doubling time and the "rule of 70" to calculate the annual average % growth rate. r = 70/doubling time = 70/r 3. A different population with 40 individuals grows at an annual average rate of 5%. Calculate the time it will take for this population to double.
How about planet Earth? �Current population size: 7. 2 billion http: //www. worldometers. info/world-population/ �Current growth rate: 1. 14% �If growth stays constant, when will the population be approximately 14 billion?
Different rates in different countries �Countries are in different stages of development – some have higher population growth than others. �Carrying capacity of different nations is different �Societal, economic, and environmental factors different.
Population Pyramids