BIO_ALL IN1_StGd_tese_ch05 Name____________________________ Class __________________ Date __________ 8/7/03 5:46 PM Page 220 Name______________________________ Class __________________ Date ______________ Chapter 5 Populations Population Size Population size is the number of individuals that make up a population. Immigration and births increase population size. Emmigration and deaths decrease population size. The table below shows how several different populations have changed over a one-year time span. Look at each population and determine whether the overall population size has increased or decreased. If the population size has increased, draw an arrow that points upward (!) in the population size column. If it has decreased, draw an arrow that points downward ("). The first one has been done for you. Factors that Affect Population Size Population Births Deaths Number of Individuals that Emigrated A 200 100 0 0 B 10 10 100 0 C 1 1 1 50 D 10 100 100 10 E 100 200 0 0 F 50 1 1 50 G 10 10 0 100 Section 5–1 How Populations Grow (pages 119–123) This section identifies the characteristics used to describe a population. It also describes factors that affect population size and explains what exponential growth and logistic growth are. Characteristics of Populations (page 119) 1. What are the four main characteristics of a population? a. Geographic distribution c. Growth rate b. Density d. Age structure 2. What is a population’s geographic distribution? It is the area inhabited by the population. range . 4. What is population density? It is the number of individuals per unit area. 3. Another term for geographic distribution is Number of Individuals that Immigrated Population Size ! of individuals Population density = Number Unit area Population Growth (page 120) 6. Circle the letter of each sentence that is true about populations. a. They can grow rapidly. b. They can decrease in size. c. They may stay the same size from year to year. d. They stay the same size until they disappear. 7. What three factors can affect population size? a. The number of births b. The number of deaths c. The number of individuals that enter or leave the population 8. If more individuals are born than die in any period of time, how will the population change? It will grow. 9. Complete the table about changes in population. 2. A food shortage causes many members of a population to leave an area. What type of population movement does this describe? Circle the correct answer. emigration immigration © Pearson Education, Inc., publishing as Pearson Prentice Hall. 45 CHANGES IN POPULATION Type of Change Definition Resulting Change in Size Immigration The movement of individuals into an area The population grows Emigration The movement of individuals out of an area The population decreases © Pearson Education, Inc. All rights reserved. Use the table to answer the question. 1. Look at population G. How would the population size have changed if 100 individuals had also emigrated? 5. What is the equation with which you can calculate population density? Population Growth Model 3 – Growth Curves Diagram A—Exponential Growth Curve How is population growth naturally regulated? Diagram B—Logistic Growth Curve Why? The current world population is estimated to be over 7 billion. At present the number of births annually exceeds the number of deaths, which means that the population is increasing, and is estimated to reach 9 billion by 2040. In 1750 the world population was estimated at less than 800 million. How are growing populations such as ours controlled and supported, and can they continue to grow indefinitely? B) Lag phase Total Population s ath De ) (D Exponential growth Time Em igr ati on Population Numbers (I) on ati s( m igr rth Im Bi Population Numbers Model 1 – Population Growth Carrying capacity (K) Pressure begins due to environmental resistance Lag phase Time 9. Refer to Model 3. (E a. During what phase of the growth curves in each diagram is the population just beginning to colonize an area? ) b. Which type of population growth appears to continue unchecked? 1. Refer to Model 1. a. What is the term used for populations moving into an area? b. What is the term used for populations leaving an area? 10. The growth curves in Model 3 are often referred to using the letters of the alphabet they resemble. The logistic growth curve is sometimes referred to as an S-curve. What letter would you use to describe the exponential growth curve? c. Name two factors that cause an increase in the population size. 11. What causes the population to slow down during logistic growth? d. Name two factors that cause a decrease in population size. 12. The maximum population an environment can sustain is affected by environmental factors that cause the population to level out or become stable. What term is used to describe this level of logistic growth? Population Growth 1 4 POGIL™ Activities for High School Biology 13. Propose some reasons why population growth is so rapid immediately after the lag phase in both diagrams of Model 3? 14. Exponential growth (diagram A) refers to the phenomena of populations that double in size every generation. If you start with a single bacterium capable of dividing every 20 minutes, how many bacteria would you have after just four hours? 15. In most natural populations rapid exponential growth is unsustainable. As populations increase, environmental resistance causes the growth rate to slow down, until carrying capacity is reached. With your group, brainstorm several factors that could be considered as environmental resistance. 16. Diagram B shows that the population size fluctuates around the carrying capacity. Considering what you know about interactions in the environment, discuss with your group some of the factors that could cause these fluctuations. In your answer you should relate these factors to the information from Model 1. Population Growth 5 BIO_ALL IN1_StGd_tese_ch05 8/7/03 5:46 PM Page 221 Name______________________________ Exponential Growth BIO_ALL IN1_StGd_tese_ch05 Class __________________ Date ______________ 8/7/03 5:46 PM Page 222 Name______________________________ Class __________________ Date ______________ (page 121) 10. How will a population change if there is abundant space and food and if the population is protected from predators and disease? The population will multiply, and the population size will increase. 11. When does exponential growth occur? It occurs when individuals in a population reproduce at a constant rate. 12. What are three ways that a growth rate may be stated, or expressed? It may be stated as a doubling time, a birthrate per female, or a percentage of growth per year. 13. Under ideal conditions with unlimited resources, how will a population grow? Such a population would grow exponentially. 18. When does logistic growth occur? It occurs when a population’s growth slows or stops following a period of exponential growth. 19. Circle the letter of each instance when a population’s growth will slow down. a. The birthrate and death rate are the same. b. The birthrate is greater than the death rate. c. The rate of immigration is equal to the rate of emigration. d. The rate of emigration is less than the rate of immigration. 20. What is the carrying capacity of the environment for a particular species? It is the largest number of individuals that the given environment can support. 14. Complete the graph by drawing the characteristic shape of exponential population growth. 21. Complete the graph by drawing the characteristic shape of logistic population growth. Exponential Growth of Bacterial Population Logistic Growth of Yeast Population 300,000 Number of Yeast Cells Number of Bacteria Carrying capacity 200,000 100,000 0 0 2 4 6 15. Is the following sentence true or false? Elephants never grow exponentially because their rate of reproduction is so slow. Logistic Growth false (page 122) 16. Circle each sentence that is true about exponential growth. a. It continues until the organism covers the planet. b. It continues at the same rate as resources become less available. c. It does not continue in natural populations for very long. d. It continues in natural populations until the birthrate increases. 17. When resources become less available, how does population growth change? It slows or stops. Time (hours) © Pearson Education, Inc. All rights reserved. © Pearson Education, Inc. All rights reserved. Time (hours) Name____________________________ Class __________________ Name Date __________ Class Date Chapter 5 Populations Density-Dependent and Density-Independent Limiting Factors Density-dependent limiting factors limit a population when the population density reaches a certain level. Density-independent limiting factors affect a population in the same way no matter how big or small it is. Read the information in the table. Limiting Factor Brief Description of the Limiting Factor Extreme Climate Changes Drought and other extreme climate changes can cause members of a population to die off rapidly. Competition Individuals of the same species compete with each other for resources. Human Disturbances Graphic Organizer Concept Map Using information from the chapter, complete the concept map below. If there is not enough room in the concept map to write your answers, write them on a separate sheet of paper. Population Limiting Factors include 1. 2. Human activity, like damming a river, can harm many populations in an ecosystem. Parasites limit the growth of a population by taking nourishment from their hosts. In the spaces provided, label each limiting factor as either densitydependent or density-independent. Extreme climate changes Competition Human disturbances Parasitism Use the table to answer the question. 1. Give another example of an extreme climate change that might limit the growth of a population. © Pearson Education, Inc., publishing as Pearson Prentice Hall. 48 affect populations 3. © Pearson Education, Inc. All rights reserved. Parasitism affect populations 4. examples include Competition 5. 7. Teaching Resources /Chapter 5 examples include Parasitism Natural disasters 6. 8. Human activities 61 Name____________________________ Class __________________ Date __________ Predator-Prey Relationships A predator is an animal that eats other animals. Prey is the animal that gets eaten. Predator-prey interactions can affect the population growth of both the predator and the prey. In the graph below, the wolves are the predators and the moose are the prey. Follow the prompts to help you analyze the graph. • Circle the part of the line representing the moose population from the years 1964 to 1974 in red. • Circle the part of the line representing the wolf population from the years 1969 to 1980 in blue. 2400 50 2000 40 1600 30 1200 20 800 10 400 0 1955 0 1960 1965 1970 1975 1980 1985 1990 1995 Year Wolves Moose Use the graph to answer the questions. 1. Was the moose population increasing or decreasing from 1964 to 1974? 2. Was the wolf population increasing or decreasing from 1969 to 1980? 3. Why might changes in the moose population from 1964 to 1974 relate to changes in the wolf population from 1969 to 1980? © Pearson Education, Inc., publishing as Pearson Prentice Hall. 49 Number of Moose Number of Wolves Wolf and Moose Populations on Isle Royale 60

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