4.1 Section Objectives – page 91 Compare and contrast exponential and linear population growth. Compare and contrast exponential and linear population growth. Section Objectives: Relate the reproductive patterns of different populations of organisms to models of population growth. Relate the reproductive patterns of different populations of organisms to models of population growth. Predict effects of environmental factors on population growth. Predict effects of environmental factors on population growth.

Section 4.1 Summary – pages A population is a group of organisms, all of the same species, that live in a specific area. A population is a group of organisms, all of the same species, that live in a specific area. A healthy population will grow and die at a steady rate unless it runs out of food or space, or is attacked in some way by disease or predators. A healthy population will grow and die at a steady rate unless it runs out of food or space, or is attacked in some way by disease or predators. Principles of Population Growth Scientists study changes in populations in a variety of ways. Scientists study changes in populations in a variety of ways.

Section 4.1 Summary – pages One method involves introducing organisms into an environment that contains abundant resources and then watching how the organisms react. One method involves introducing organisms into an environment that contains abundant resources and then watching how the organisms react. Principles of Population Growth

Section 4.1 Summary – pages Studies of populations of larger organisms, such as an elk population in a national park, require methods such as the use of radio monitors. Studies of populations of larger organisms, such as an elk population in a national park, require methods such as the use of radio monitors. Principles of Population Growth

Section 4.1 Summary – pages The growth of populations is unlike the growth of pay you get from a job. The growth of populations is unlike the growth of pay you get from a job. Populations of organisms, do not experience linear growth. Rather, the graph of a growing population starts out slowly, then begins to resemble a J-shaped curve. Populations of organisms, do not experience linear growth. Rather, the graph of a growing population starts out slowly, then begins to resemble a J-shaped curve. How fast do populations grow?

Population Growth of Houseflies 1 million 500, One year Population size

Section 4.1 Summary – pages The initial increase in the number of organisms is slow because the number of reproducing individuals is small. The initial increase in the number of organisms is slow because the number of reproducing individuals is small. Soon, however, the rate of population growth increases because the total number of individuals that are able to reproduce has increased. Soon, however, the rate of population growth increases because the total number of individuals that are able to reproduce has increased. How fast do populations grow?

Section 4.1 Summary – pages A J-shaped growth curve illustrates exponential population growth. A J-shaped growth curve illustrates exponential population growth. Exponential growth means that as a population gets larger, it also grows at a faster rate. Exponential growth means that as a population gets larger, it also grows at a faster rate. Is growth unlimited? Exponential growth results in unchecked growth. Exponential growth results in unchecked growth.

Section 4.1 Summary – pages Limiting factors, such as availability of food, disease, predators, or lack of space, will cause population growth to slow. Limiting factors, such as availability of food, disease, predators, or lack of space, will cause population growth to slow. Under these pressures, the population may stabilize in an S-shaped growth curve. Under these pressures, the population may stabilize in an S-shaped growth curve. What can limit growth?

Section 4.1 Summary – pages What can limit growth? Characteristics of Population Growth Exponential growth Carrying capacity J curve S curve Population Time 0 DISEASE SPACEPREDA- TORS FOOD

Section 4.1 Summary – pages The number of organisms of one species that an environment can support indefinitely is its carrying capacity. The number of organisms of one species that an environment can support indefinitely is its carrying capacity. When a population overshoots the carrying capacity, then limiting factors may come into effect. When a population overshoots the carrying capacity, then limiting factors may come into effect. Carrying capacity

Section 4.1 Summary – pages Carrying capacity Deaths begin to exceed births and the population falls below carrying capacity. Deaths begin to exceed births and the population falls below carrying capacity. Carrying capacity

Section 4.1 Summary – pages Biologists study the factor that determines population growth—an organism’s reproductive pattern, also called its life-history pattern. Biologists study the factor that determines population growth—an organism’s reproductive pattern, also called its life-history pattern. Reproduction Patterns In nature, animal and plant populations change in size. In nature, animal and plant populations change in size. A variety of population growth patterns are possible in nature. A variety of population growth patterns are possible in nature.

Section 4.1 Summary – pages Rapid life-history organisms have a small body size, mature rapidly, reproduce early, and have a short life span. Rapid life-history organisms have a small body size, mature rapidly, reproduce early, and have a short life span. Rapid life-history patterns Rapid life-history patterns are common among organisms from changeable or unpredictable environments. Rapid life-history patterns are common among organisms from changeable or unpredictable environments.

Section 4.1 Summary – pages Slow life-history patterns Large species that live in more stable environments usually have slow life-history patterns. Large species that live in more stable environments usually have slow life-history patterns.

Section 4.1 Summary – pages Slow life-history organisms reproduce and mature slowly, and are long-lived. They maintain population sizes at or near carrying capacity. Slow life-history organisms reproduce and mature slowly, and are long-lived. They maintain population sizes at or near carrying capacity. Slow life-history patterns

Section 4.1 Summary – pages Three patterns of dispersal are random, clumped, and uniform. Three patterns of dispersal are random, clumped, and uniform. Density factors and population growth How organisms are dispersed can be important. How organisms are dispersed can be important. Random Clumped Uniform

Section 4.1 Summary – pages Population density describes the number of individuals in a given area. Population density describes the number of individuals in a given area. Density factors and population growth Ecologists have identified two kinds of limiting factors that are related to dispersal: density- dependent and density-independent factors. Ecologists have identified two kinds of limiting factors that are related to dispersal: density- dependent and density-independent factors.

Section 4.1 Summary – pages Disease, for example, can spread more quickly in a population with members that live close together. Disease, for example, can spread more quickly in a population with members that live close together. Density-dependent factors include disease, competition, predators, parasites, and food. Density-dependent factors include disease, competition, predators, parasites, and food. Density factors and population growth

Section 4.1 Summary – pages Most density- independent factors are abiotic factors, such as temperature, storms, floods, drought, and major habitat disruption. Most density- independent factors are abiotic factors, such as temperature, storms, floods, drought, and major habitat disruption. Density-independent factors can affect all populations, regardless of their density. Density-independent factors can affect all populations, regardless of their density. Density factors and population growth

Section 4.1 Summary – pages Organism Interactions Limit Population Size Population sizes are limited not only by abiotic factors, but also are controlled by various interactions among organisms that share a community. Population sizes are limited not only by abiotic factors, but also are controlled by various interactions among organisms that share a community.

Section 4.1 Summary – pages Predation affects population size When a predator consumes prey on a large enough scale, it can have a drastic effect on the size of the prey population. When a predator consumes prey on a large enough scale, it can have a drastic effect on the size of the prey population. Populations of predators and their prey are known to experience cycles or changes in their numbers over periods of time. Populations of predators and their prey are known to experience cycles or changes in their numbers over periods of time.

Section 4.1 Summary – pages Predation affects population size The data in this graph reflect the number of hare and lynx pelts sold to the Hudson’s Bay Company in northern Canada from 1845 through The data in this graph reflect the number of hare and lynx pelts sold to the Hudson’s Bay Company in northern Canada from 1845 through Lynx and Hare Pelts Sold to the Hudson’s Bay Company Number of organisms(in thousands) Times (in years) Lynx Hare

Section 4.1 Summary – pages In field studies, predation increases the chance that resources will be available for the remaining individuals in a prey population. In field studies, predation increases the chance that resources will be available for the remaining individuals in a prey population. Predation affects population size

Section 4.1 Summary – pages Competition within a population Competition is a density-dependent factor. Competition is a density-dependent factor. When only a few individuals compete for resources, no problem arises. When only a few individuals compete for resources, no problem arises. When a population increases to the point at which demand for resources exceeds the supply, the population size decreases. When a population increases to the point at which demand for resources exceeds the supply, the population size decreases.

Section 4.1 Summary – pages The effects of crowding and stress When populations of certain organisms become crowded, individuals may exhibit symptoms of stress. When populations of certain organisms become crowded, individuals may exhibit symptoms of stress. As populations increase in size in environments that cannot support increased numbers, individual animals can exhibit a variety of stress symptoms. As populations increase in size in environments that cannot support increased numbers, individual animals can exhibit a variety of stress symptoms.

Section 4.1 Summary – pages These include aggression, decrease in parental care, decreased fertility, and decreased resistance to disease. These include aggression, decrease in parental care, decreased fertility, and decreased resistance to disease. They become limiting factors for growth and keep populations below carrying capacity. They become limiting factors for growth and keep populations below carrying capacity. The effects of crowding and stress

Section 1 Check Question 1 Exponential growth means that as a population gets larger, it also _____. Exponential growth means that as a population gets larger, it also _____. D. stabilizes in an S-shaped growth curve C. grows at a steady rate B. grows at a faster rate A. grows at a slower rate

Section 1 Check The answer is B. A J-shaped growth curve illustrates exponential growth. Population Growth of Houseflies 1 million 500, One year Population size

Section 1 Check Question 2 Which of the following would you expect to observe after a population exceeds its carrying capacity? Which of the following would you expect to observe after a population exceeds its carrying capacity? D. population growth rate is unaffected by limiting factors C. deaths exceed births B. births exceed deaths A. population increases exponentially

Section 1 Check The answer is C. Limiting factors may come into effect after a population exceeds its carrying capacity. Deaths begin to exceed births and the population falls below carrying capacity. Characteristics of Population Growth Exponential growth J curve S curve Population Time 0 DISEASE SPACE PREDATORS FOOD Carrying capacity

Section 1 Check Question 4 The number of organisms of one species that an environment can support indefinitely is its _____. The number of organisms of one species that an environment can support indefinitely is its _____. D. carrying capacity C. demographic B. growth rate A. life-history pattern

Section 1 Check The answer is D. If population size rises above the carrying capacity, more organisms die than are born and the population drops back below the carrying capacity. Carrying capacity

4.2 Section objectives– page 100 Identify how the birthrate and death rate affect the rate at which a population changes. Identify how the birthrate and death rate affect the rate at which a population changes. Section Objectives: Compare the age structure of rapidly growing, slow-growing, and no-growth countries. Compare the age structure of rapidly growing, slow-growing, and no-growth countries. Explain the relationship between a population and the environment. Explain the relationship between a population and the environment.

Section 4.2 Summary – page Section 4.2 Summary – page In the United States, a census is taken every ten years. In the United States, a census is taken every ten years. World Population One of the most useful pieces of data is the rate at which each country’s population is growing or declining. One of the most useful pieces of data is the rate at which each country’s population is growing or declining. These figures are the basis for demography, the study of human population size, density and distribution, movement, and its birth and death rates. These figures are the basis for demography, the study of human population size, density and distribution, movement, and its birth and death rates.

Section 4.2 Summary – page Human population growth is different because humans have the ability to change their environment. Human population growth is different because humans have the ability to change their environment. Human population growth People live longer and are able to produce offspring that live long enough to produce offspring, hence, a population grows. People live longer and are able to produce offspring that live long enough to produce offspring, hence, a population grows.

Section 4.2 Summary – page There are a number of factors that determine population growth rate. There are a number of factors that determine population growth rate. Calculating growth rate These are births, deaths, immigration and emigration. These are births, deaths, immigration and emigration. Birthrate is the number of live births per 1000 population in a given year. Birthrate is the number of live births per 1000 population in a given year.

Section 4.2 Summary – page Death rate is the number of deaths per 1000 population in a given year. Death rate is the number of deaths per 1000 population in a given year. Movement of individuals into a population is immigration. Movement of individuals into a population is immigration. Calculating growth rate

Section 4.2 Summary – page Movement out of a population is emigration. Movement out of a population is emigration. Birthrate – Death rate = Population Growth Rate (PGR) Birthrate – Death rate = Population Growth Rate (PGR) If the birth rate of a population equals its death rate, then the population growth rate is zero. If the birth rate of a population equals its death rate, then the population growth rate is zero. Calculating growth rate

Section 4.2 Summary – page If the PGR is above zero, more new individuals are entering the population than are leaving, so the population is growing. If the PGR is above zero, more new individuals are entering the population than are leaving, so the population is growing. A PGR can also be less than zero. A PGR can also be less than zero. Calculating growth rate

Section 4.2 Summary – page Another quantitative factor that demographers look at is the doubling time of a population. Another quantitative factor that demographers look at is the doubling time of a population. Doubling time is the time needed for a population to double in size. Doubling time is the time needed for a population to double in size. The time it takes for a population to double varies depending on the current population and growth rate. The time it takes for a population to double varies depending on the current population and growth rate. Doubling time

Section 4.2 Summary – page Doubling time can be calculated for the world, a country, or even a small region, such as a city. Doubling time can be calculated for the world, a country, or even a small region, such as a city. Doubling time

Section 4.2 Summary – page Age structure Population Distribution Per Age Range for Several Countries Age Stable growth Rapid growth Slow growth Male Female Reproductive years Population (percent of total for each country)

Section 4.2 Summary – page The needs of populations differ greatly throughout the world. The needs of populations differ greatly throughout the world. Sometimes, a population grows more rapidly than the available resources can handle. Sometimes, a population grows more rapidly than the available resources can handle. Ecology and growth

Section Summary – page Ecology and growth Resources that are needed for life, such as food and water, become scarce or contaminated. Resources that are needed for life, such as food and water, become scarce or contaminated.

Section Summary – page The amount of waste produced by a population becomes difficult to dispose of properly. The amount of waste produced by a population becomes difficult to dispose of properly. These conditions can lead to stress on current resources and contribute to the spread of diseases that affect the stability of human populations both now and to come. These conditions can lead to stress on current resources and contribute to the spread of diseases that affect the stability of human populations both now and to come. Ecology and growth

Section 2 Check What is the study of human population size, density and distribution, movement, and birth and death rates called? What is the study of human population size, density and distribution, movement, and birth and death rates called? Question 1 D. biodiversity C. phylogeny B. demography A. ecology

Section 2 Check The answer is B. When various demographic data are monitored, societies are able to improve environmental conditions and quality of life.

Section 2 Check Which interval in the diagram below represents the population reaching equilibrium near carrying capacity? Which interval in the diagram below represents the population reaching equilibrium near carrying capacity? Question 3 D. 4 C. 3 B. 2 A. 1

Section 2 Check The answer is D. The number of organisms tends to rise above and fall below the carrying capacity due to limiting factors.