Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings UNIT 5: POPULATIONS Environmental Science

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Populations Population- all of the organisms within a species that interact in a specific area and at a specific time –Genetic Diversity- similar but different due to DNA –Affected by: Size Age distribution Density Genetic composition

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Principles of Ecological Factors Abiotic Factors- all of the nonliving parts in an ecosystem Biotic Factors-all of the living factors in an ecosystem Range of Tolerance- any variation in the physical or chemical environment that an organism can withstand before it is killed/harmed –Law of tolerance-the existence, abundance, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Regulating Population Growth Limiting Factors- a distinguishing chemical or physical factor that regulates the population growth of a species; more specific than any other factor –Limiting Factor Principle- Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance. Niche- an organisms functional role within an ecosystem; everything that affects the survival and reproduction –Range of tolerance; resources it utilizes (food, space); interaction with other biota and abiotic factors; its role in the food web/matter cycle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 4-13 Page 73 Terrestrial Ecosystems Aquatic Life Zones Sunlight Temperature Precipitation Wind Latitude Altitude Fire frequency Soil Light penetration Water currents Dissolved nutrient concentrations (especially N and P) Suspended solids Salinity Abiotic Factors That Impact Populations

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Biotic Components of Ecosystems Fig p. 75 Producers (autotrophs) Consumers (heterotrophs) Decomposers

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Population Ecology Population- how to measure? Growth rates: J shaped, S shaped K, r, and reproductive strategies Human population

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Population density = number of individuals in a given area or volume count all the individuals in a population estimate by sampling How are populations measured?

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings mark-recapture method depends on likelihood of recapturing the same individual Figure 35.2A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The dispersion pattern of a population refers to the way individuals are spaced within their area –Clumped - –Uniform: –Random: no pattern

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.2C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Idealized models describe two kinds of population growth 1. exponential growth 2. logistic growth How do populations grow?

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A J-shaped growth curve, described by the equation G = rN, is typical of exponential growth –G = the population growth rate –r = the intrinsic rate of increase, or an organism's maximum capacity to reproduce –N = the population size

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.3A

Time (years) Population size r = 0.06 r = 0.02 r = 0 r = high intrinsic rate of increase low intrinsic rate of increase zero population growth negative intrinsic rate of increase

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2. Logistic growth is slowed by population- limiting factors K = Carrying capacity is the maximum population size that an environment can support Figure 35.3B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings logistic growth curve –K = carrying capacity –The term (K - N)/K accounts for the leveling off of the curve Figure 35.3C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings declining birth rate or increasing death rate The regulation of growth in a natural population is determined by several factors –limited food supply –the buildup of toxic wastes –increased disease –predation Multiple factors may limit population growth

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –About every 10 years, both hare and lynx populations have a rapid increase (a "boom") followed by a sharp decline (a "bust") Figure 35.5

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Survivorship curves plot the proportion of individuals alive at each age Three types of survivorship curves reflect important species differences in life history Figure 35.6

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An organism's life history is the series of events from birth through reproduction to death Life history traits include –the age at which reproduction first occurs –the frequency of reproduction –the number of offspring –the amount of parental care given –the energy cost of reproduction Evolution shapes life histories

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Principles of population ecology may be used to –manage wildlife, fisheries, and forests for sustainable yield –reverse the decline of threatened or endangered species –reduce pest populations –IPM = Integrated Pest Management

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Integrated pest management (IPM) uses a combination of biological, chemical, and cultural methods to control agricultural pests IPM relies on knowledge of –the population ecology of the pest –its associated predators and parasites –crop growth dynamics

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In 1890, a group of Shakespeare enthusiasts released about 120 starlings in New York's Central Park The Spread of Shakespeare's Starlings

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Today: over 100 million starlings, spread over N. Amer. Current Current

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The starling population in North America has some features in common with the global human population –Both are expanding and are virtually uncontrolled –Both are harming other species

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings doubled three times in the last three centuries about 6.1 billion and may reach 9.3 billion by the year 2050 improved health and technology have lowered death rates THE HUMAN POPULATION

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The history of human population growth Figure 35.8A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.9B RAPID GROWTH Kenya MaleFemale Percent of population SLOW GROWTH United States MaleFemale ZERO GROWTH/DECREASE Italy MaleFemale Ages 45+ Ages 15–44 Under 15 Ages 45+ Ages 15–44 Also reveals social conditions, status of women The age structure of a population is the proportion of individuals in different age-groups

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The ecological footprint represents the amount of productive land needed to support a nation’s resource needs The ecological capacity of the world may already be smaller than its ecological footprint

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ecological footprint in relation to ecological capacity Figure 35.8B

U.S. China India Russia Japan U.S. China India Russia Japan Per capita CO 2 emissions (metric tons of carbon) Total CO 2 emissions (billion metric tons of carbon)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 34 Part 1: Population Growth

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 35 Current Birth and Death Rates Every second: about 4 children are born, while about 2 other people die Net gain: 2.3 humans added to the world population every second, 72 million added every year

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 36 Human Population Levels Throughout History ADD FIG. 4.2

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 37 ADD TABLE 4.1

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 38 Part 2: Limits to Growth Varying Perspectives Overpopulation causes resource depletion and environmental degradation Human ingenuity and technology will allow us to overcome any problems - more people may be beneficial Resources are sufficient to meet everyone's needs - shortages are the result of greed, waste, and oppression

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 39 Decisions on how many children to have are influenced by many factors, including culture, religion, politics, need for old-age security, and immediate family finances.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 40 Part 3: Human Demography Demography - vital statistics about people, such as births and deaths Two demographic worlds Less-developed counties represent 80% of the world population, but more than 90% of projected growth Richer countries tend to have negative growth rates

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 41

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 42 By 2050, India will probably be the world's most populous country. (297)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 43 Fertility and Birth Rates Fecundity - physical ability to reproduce Fertility - the actual production of offspring Crude birth rate - number of births per year per thousand people Total fertility rate - number of children born to an average woman during her reproductive life Zero population growth (ZPG) - occurs when births + immigration just equal deaths + emigration

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 44 Regional Declines in Total Fertility Rates

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 45 China's one-child- per-family policy decreased the country's fertility rate from 6 to 1.8 in two decades. However, the policy is very controversial.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 46

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 47 As incomes rise, so does life expectancy.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 48 Living Longer: Demographic Implications A population growing by natural increase has more young people than does a stationary population. Dependency ratio - the number of nonworking individuals compared to working individuals - declining in countries such as the U.S. and Japan If current trends continue, by 2100 the median age in the U.S. will be 60.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 49

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 50 Part 4: Population Growth - Opposing Factors Pronatalist pressures Factors that increase people's desires to have children Birth reduction pressures Factors that tend to reduce fertility

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 51 U.S. Birth Rates:

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 52 Part 5: Demographic Transition Optimistic view - world population will stabilize during this century Pessimistic view - poorer countries of the world are caught in a "demographic trap" - helping poor countries will only further threaten the earth's resources Social justice view - overpopulation due to a lack of justice, not resources

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 53 Demographic Transition Accompanying Economic and Social Development

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 54 Fig. 4.13

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 55 Infant Mortality and Women's Rights

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 56 Part 7: The Future of Human Populations

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 2.10x