Graphing Change s in Population Changes in a popula tions size can be displa y

# Graphing change s in population changes in a popula

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Graphing Change s in Population Changes in a popula- tion’s size can be d ispla y e d on a line graph. Figure 7 sho w s a graph of the changes in a rabbit population. The vertical axis sho w s the numbers of rabbits in the population, w hile the hori- zontal axis sho w s time. The graph sho w s the size of the popula- tion over a ten- y ear perio d . If birth rate death rate, population size increases. If death rate birth rate, population size decreases. Inequalities The population statement is an example of an inequality. An inequality is a mathemati- cal statement that compares two expressions. Two signs that represent inequalities are < (is less than) > (is greater than) For example, an inequality comparing the fraction to the decimal 0.75 would be written Practice Problems Write an inequality comparing each pair of expressions below. 1. 5 6 2. 0.4 3. 2 ( 8) 7 1.5 1 2 -- 0.75 3 5 -- Differentiated Instruction Calculating Growth Rate Materials none Time 5 minutes Focus Review with students the definitions of birth rate and death rate. TeachAsk: Suppose 1,600 snow geese died in the same year that 1,400 were born. What would the growth rate be for that year?(Tell students that birth rate – death rate = growth rate: b – d = g.1,400 1,600 = growth rate of 200 geese for that year) What does a negative growth rate mean?(The population is declining.) ApplyAsk: What might account for a death rate that is higher than the birth rate? (Possible answers: Disease; not enough food; being eaten by other animals; unfavorable environmental conditions)learning modality: logical/mathematicalChangesin a Rabbit Population For: Changes in Population Activity Visit: PHSchool.com Web Code: cep-5012 Students investigate the factors influencing changes in population size. Gifted and Talented Calculating Growth Rate Tell students that ecologists use the birth and death rates to calculate a population’s growth rate, the rate at which the population is changing. The birth rate (b) minus the death rate (d) L3 equals the growth rate (g): b d = g. Have students use this formula to calculate the growth rate of rabbits discussed in the text. (600 births 400 deaths = a growth rate of 200 rabbits per year) learning modality: logical/mathematical Monitor Progress L2 Writing Have each student write a paragraph explaining how birth rate and death rate affect the size of a population. Students can save their paragraphs in their portfolios. Answer Figure 7 Fourth year of the study; about 850 L2 Year of Study Number of Rabbits (thousands) 0 1 2 3 4 5 6 7 8 9 10 900 800 700 600 500 400 300 200 100 From Year 4 to Year 8, more rabbits left the population than joined it, so the population decreased. F IGURE 7 This line graph shows how the size of a rabbit population changed over a ten-year period.  • • • 