Systems of Change And Populations

Key Terms System: Feedback: Why is it important to understand feedback in terms of environmental systems?

What is the difference between a positive and negative feedback?

Example: Ice Melting due to increased temperature

Exponential Growth Population Clock: http://www.census.gov/popclock/

Causes of human population growth In the last century: Increased sanitation Medical advances

Doubling Time Time needed to double the number of individuals in a population. Rule of 70 Doubling time = 70/growth rate Year Population In billions Doubling Time (years) 1804 1 -- 1927 2 123 1959 3 32 1974 4 15 1987 5 13 1999 6 12 2012 7 2026 8 14 2042 9 16

Calculating Exponential Growth N = N0ekt N = future population N0 = present population = e = 2.71828 k = R/100 R = 1.14% t = time Given these values, what will the Earth’s population be in: 50 years? 100 years? 200 years?

Reflection What are the problems that occur because of human population growth? What can we do to fix these problems? What do we need to know to fix these problems?

Average Residence Time (ART) What is it? See page 44 – 45: What would the ARTwater of the Gods Eye be which is 246,000,000 m3 of water, and equal input and output rates of 23 m3/sec? What would the ARTwater of Long Lake which has half of the reservoir volume but twice the input and output rates of the Gods Eye? The concentration of MTBE in both lakes is 10μg/l what is the ART of MTBE in both lakes?

Reflection What can the ART of a substance tell us about the environment?

Forecasting population change P2 = P1 + (B – D) + (I – E) P2 = population at time 2 P1 = population at time 1 B = number of births D = number of deaths I = number of immigrants E = number of emigrants What is P2 if: P1 = 1,580,971 B = 26,178 D = 4,127 I = 56,248 E = 61,974 Is the population growing or shrinking? What is causing this change?

What are the birth and death rates of our population? Birth Rate Death Rate b = B/ P2 d = D/ P2

Growth rate g = (B-D)/P2 What is the growth rate of our sample population?

Reflection Why does the growth rate not include immigration and emigration? What factors can affect the growth rate of a population? How do they affect the population?

AP Question: A country with an annual population growth rate of 5% would double in population in approximately how many years? 5 years 7 years 14 years 70 years 350 years EXPLAIN your choice

AP Question: The world’s current population of approximately 7 billion people with a growth rate of about 1.3% represents a doubling time of about 54 years. At this rate, according to current projections, the global population will be likely to reach between 7.5 and 10.5 billion by 2050. Which of the following would NOT be a viable strategy for ensuring adequate nutrition for a population that size? Where feasible, switch to drip irrigation Increase the efficiency of food distribution networks Produce more meat products while decreasing the amount of land devoted to grain and crop production Develop new hybrid crops that are more drought and pest resistant Expand the use of non-toxic and environmentally-friendly methods of pest control EXPLAIN your answer

AP Question Worldwide human population growth within the last 100 years is primarily due to Increase in birth rate Decrease in death rate Lower infant mortality rate Immigration A desire to have more children EXPLAIN you answer