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Chapter 45 Population Ecology Ecology: Overview: Earth’s Fluctuating Populations: To understand _____________________________ We must consider the general principles of _____________________ _____________________________, including the human population, can continue to grow indefinitely Population ecology Including environmental influences on population _______________________and __________________________, ______________________________, and variations in population size The fur seal population of St. Paul Island, off the coast of Alaska is one that has experienced dramatic fluctuations in size Concept 52.1: Dynamic biological processes influence population _______________________, ________________________, and ________________________________ A population: Density Dispersion Density: A dynamic perspective Determining the ________________________ of natural population is possible, but difficult to accomplish In most cases it is impractical or impossible to count _______________________________Density is the result of a dynamic interplay Between processes that add individuals to a population (________________________) and those that remove individuals from it (_______________________) in a population Patterns of Dispersion Environmental and __________________________ factors Influence the _____________________ of individuals in a population A clumped dispersion Is one in which individuals aggregate in ___________________________ May be influenced by resource _____________________________ and _____________ __________________________________ are often found together because it favors soil conditions and other environmental factors A uniform dispersion Is one in which individuals are ________________________________ May be influenced by social interactions such as_______________________________________ Some ____________________________ produce chemicals to inhibit the germination and growth of nearby individuals that compete for resources. A random dispersion is one in which the position of each individual is ________________________ of other individuals (c) Random. Dandelions grow from windblown seeds that land at random and later germinate. Demography __________________________is the study of the vital statistics of a population and how they change over time ____________________ rates and_____________________________ rates are of particular interest to demographers Life Table A life table: Life table of Belding’s Squirrel Survivorship Curves A survivorship curve Survivorship Curve can be classified in three types _____________________________ is flat at the start, reflecting low death rates during early and middle life and drops steeply as many older individuals die _______________________________ are this curve because produce few individuals are provide good care ____________________________: Constant death over an individual life span Examples: _______________________________: drops sharply at the start, reflecting very high death rates for the young, but flattens out as death rate declines for those individuals that survived to a certain critical period • Survivorship curves can be classified into three general types Number of survivors (log scale) – Type I, Type II, and Type III 1,000 I 100 II 10 III 1 0 Figure 52.5 50 Percentage of maximum life span 100 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The survivorship curve for Belding’s ground squirrels: Shows that the death rate is relatively _____________________ _______________________________ Survivorship Curve Reproductive Rates A reproductive table, or ___________________schedule is an age-specific summary of the reproductive rates in a __________________________ • A reproductive table Describes the _______________of a population Concept 52.2: Life history traits are products of ______________________________________ Life history traits are ______________________________ Reflected in the ____________________________________________________________ of an organism Three basic variable: When reproduction ___________________, how ____________________________an organism reproduces, and _____________________ offspring are reproduce Life histories are very __________________________. Species that exhibit _______________________________, or “big-bang” reproduction : Reproduce a single ________________________________________ Species that exhibit ____________________________, or repeated reproduction: Produce offspring repeatedly ___________________________________ Trade off and Life Histories Which may lead to trade-offs between ____________________________________ Showed that survival was _____________________ to parents caring for their young. Some plants produce a ___________________________ number of small __________________: ensuring that at least some of them will grow and eventually reproduce Other types of plants produce a moderate number of __________________seeds That provide a large store of energy that will help seedlings become established Parental care of smaller broods may also facilitate ________________________________ Concept 52.3: The ____________________________ model describes population growth in an idealized, unlimited environment It is useful to study population growth in an idealized situation In order to understand the capacity of species for increase and the conditions that may facilitate this type of growth Per Capita Rate of Increase If immigration and emigration are ignored A ______________________________________ (per capita increase) equals birth rate minus death rate _______________________ population growth : Occurs when the birth rate equals the death rate The population growth equation can be expressed as Exponential Growth ____________________________ population growth: Is population increase under idealized conditions Under these conditions: The rate of reproduction is at its maximum, called the ______________________________________ The equation of exponential population growth is Exponential population growth results in a ___________________________________ The J-shaped curve of exponential growth is characteristic of some _____________________________ that are rebounding Concept 52.4: The logistic growth model includes the concept of carrying capacity Exponential growth: Cannot be sustained for _________________ in any population A more realistic population model limits growth by incorporating _____________________________ Carrying capacity (K): Logistic Growth Model In the ________________________________________________________ the per capita rate of increase declines as carrying capacity is reached We construct the logistic model by starting with the __________________________________________ And adding an expression that reduces the per capita rate of increase as _________________ increases The logistic growth equation includes K, the __________________________ Hypothetical example of logistic growth The logistic model of population growth produces a sigmoid (_________________________) curve Logistic model and real population The growth of laboratory populations of _____________________________ Fits an S-shaped curve Some populations overshoot K Before settling down to a relatively _________________________________ Some_______________________________ fluctuate greatly around K The logistic model fits few ___________________________________ But is useful for __________________________________ possible growth Life history traits favored by _________________________________ May vary with ___________________________________ and environmental conditions K-selection, or ______________________________________ selection Selects for life history traits that are sensitive to population density Example: ________________________________________ r-selection, or ________________________________________ selection Selects for life history traits that maximize reproduction Example: ____________________________________________________ The concepts of K-selection and r-selection Are somewhat controversial and have been criticized by ecologists as oversimplifications of the variation seen in the _________________________________________ of species Concept 52.5: Populations are regulated by a complex interaction of _______________________ and _____________________ influences There are two general questions we can ask : About regulation of ____________________________ What environmental factors stop a population from growing? Why do some populations show ______________________________________ in size over time, while others remain stable? Population Change and Population Density In density-independent populations: ____________________________ and _______________________ do not change with population density In density-dependent populations: ___________________________ fall and _________________________ rise with population density Determining equilibrium for population density Density-Dependent Population Regulation Density-dependent birth and death rates : Are an example of ________________feedback that regulates population growth Are affected by many different mechanisms Competition for Resources In crowded populations, increasing ____________________________ Intensifies intraspecific _____________________________for resources Territoriality In many ________________________________ and some invertebrates Territoriality may limit ___________________________ ___________________________are highly territorial Using ______________________ communication to warn other cheetahs of their boundaries Oceanic birds: Exhibit territoriality in _____________________________ behavior Gannets nest virtually a peck apart and defend their territories by calling and pecking at one another. Health Population density: Can influence the _____________________________ of organisms In ____________________________ populations: ___________________________can spread more rapidly Predation As a________________________ population builds up_____________________________ may feed preferentially on that species Toxic Waste The accumulation of toxic wastes can contribute to ___________________________ regulation of population size Instrinsic Factors For some populations________________________________ (physiological) factors appear to regulate population size Population Dynamics The study of _______________________________________ focuses on the complex interactions between biotic and abiotic factors that cause variation in population size Stability and Fluctuations Long-term population studies have challenged the hypothesis that populations of large mammals are______________________________________ over time Extreme fluctuations in population size are typically more common in _________________________than in large mammals Metapopulations and Immigration Metapopulations : High levels of immigration combined with higher survival can result in greater __________________________ in populations Population Cycles Many populations undergo regular _____________________________ cycles Boom-and-bust cycles are influenced by complex interactions between _______________________________ factors Concept 52.6:________________________ population growth has slowed after centuries of exponential increase No population can grow ____________________________ and humans are no exception Global Human Population The human population increased ____________________ until about 1650 and then began to grow _____________________________ Though the global population is still __________________________ The rate of growth began to slow approximately__________________ years ago Regional Patterns of Population Change To maintain population ______________________ a regional human population can exist in one of two configurations Zero population growth = High birth rates – High death rates Zero population growth = Low birth rates – Low death rates The demographic transition: The demographic transition Age Structure One important demographic factor in present and future ___________________________________ Is a country’s ___________________________, the relative number of individuals at each age Age structure is commonly represented in __________________________________ Age structure diagrams can predict a ___________________________________ Can illuminate ____________________________________ and help us plan for the future Infant Mortality and Life Expectancy _______________________________ and ________________________________ at birth vary widely among developed and developing countries but do not capture the wide range of the human condition Global Carrying Capacity Just how many humans can the biosphere support? Estimate today is: __________________________ to over 1,000 billion (1 trillion) people, with an over of _______________________________. Estimate of Carrying Capacity The _________________________________ of Earth for humans is uncertain Ecological Footprint The ecological footprint concept summarizes the _______________________ and ___________________ needed to sustain the people of a nation Is one measure of how close we are to the _________________________ of Earth Ecological footprints for 13 countries show that the countries vary greatly in their footprint size and their available ____________________________ Two conclusion were found in this graph” 1-countries vary greatly in their individual footprint size and in their available ecological capacity (the actual resource based of each country). 2- The world was already in ecological deficit when the study was conducted Overall analysis suggest that he world is not at or slightly above its carrying capacity At more than 6 billion people the world is already in ______________________________________