BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 35 Population Dynamics Modules 35.6 – 35.10

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Life tables and survivorship curves predict an individual's statistical chance of dying or surviving during each interval in its life Life tables predict how long, on average, an individual of a given age can expect to live 35.6 Life tables track mortality and survivorship in populations LIFE HISTORIES AND THEIR EVOLUTION

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –This table was compiled using 1995 data from the U.S. Centers for Disease Control Table 35.6

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Population ecologists have adopted this technique, constructing life tables for various plant and animal species

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 35.7 Evolution shapes life histories

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The effects of predation on life history traits of guppies has been tested by field experiments for several years Figure 35.7A Experimental transplant of guppies Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid” pools Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish” pools

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In nature, every population has a particular life history adapted to its environment The agave illustrates what ecologists call "big-bang reproduction" –It is able to store nutrients until environmental conditions favor reproductive success Figure 35.7B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Natural selection favors a combination of life history traits that maximizes an individual's output of viable, fertile offspring

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Selection for life history traits that maximize reproductive success in uncrowded, unpredictable environments is called r-selection –Such populations maximize r, the intrinsic rate of increase –Individuals of these populations mature early and produce a large number of offspring at a time –Many insect and weed species exhibit r-selection

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Selection for life history traits that maximize reproductive success in populations that live at densities close to the carrying capacity (K) of their environment is called K-selection –Individuals mature and reproduce at a later age and produce a few, well-cared-for offspring –Mammals exhibit K-selection

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The human population as a whole has doubled three times in the last three centuries The human population now stands at about 6.1 billion and may reach 9.3 billion by the year 2050 Most of the increase is due to improved health and technology –These have affected death rates 35.8 Connection: The human population has been growing exponentially for centuries 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 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

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The exponential growth of the human population is probably the greatest crisis ever faced by life on Earth Figure 35.8C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Population stability is achieved when there is zero population growth –Zero population growth is when birth rates equal death rates There are two possible ways to reach zero population growth (ZPG) –ZPG = High birth rates - high death rates –ZPG = Low birth rates - low death rates 35.9 Birth and death rates and age structure affect population growth

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The demographic transition is the shift from high birth and death rates to low birth and death rates –During this transition, populations may grow rapidly until birth rates decline Figure 35.9A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The age structure of a population is the proportion of individuals in different age- groups –Age structure affects population growth

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

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Age-structure diagrams not only reveal a population's growth trends –They also indicate social conditions Increasing the status and education of women may help to reduce family size

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 Connection: Principles of population ecology have practical applications

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Renewable resource management is the harvesting of crops without damaging the resource –However, human economic and political pressures often outweigh ecological concerns –There is frequently insufficient scientific information

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The collapse of the northern cod fishery –Estimates of cod stocks were too high –The practice of discarding young cod (not of legal size) at sea caused a higher mortality rate than was predicted

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Collapse of northern cod fishery Figure 35.10A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings For species that are in decline or facing extinction, resource managers try to increase population size Carrying capacity is usually increased by providing additional habitat or improving the quality of existing habitat

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Endangered species often have subtle habitat requirements –The red-cockaded woodpecker was recently recovered from near-extinction by protecting its pine habitat and using controlled fires to reduce undergrowth Figure 35.10B

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 One objective of IPM is to minimize environmental and health risks by relying on natural biological control when possible