Populationlimiting factors keep a population from increasing indefinitely. The results highlight the possibility for exogenous factors to induce pest outbreaks. This means that population growth is not affected by. So the most common density independent factor is natural disasters. This would be reasonable if, over the evolutionary timescale of interest, human populations were largely regulated by density independent factors. Densitydependent mechanisms are important drivers of population. Density dependent factors are factors that depend of the population density. Our mission is to provide a free, worldclass education to anyone, anywhere. There also exists density independent inhibition, where other factors such as weather or environmental conditions and disturbances may affect a populations carrying capacity. However, the field of population biology is different. Population and community ecology essential knowledge 2.
Pdf density dependence occurs when the population growth rate, or constituent gain. Apr 01, 2015 in case 1, all fertility and mortality rates are fixed quantities, independent of population density. Population ecology logistic population growth britannica. Students will also apply their knowledge of population growth to the human. And a lot of these, as we just talked about, you could think of them as biotic factors. Population ecology population ecology logistic population growth. What is the difference between density dependent and. Selection maximizes r here, whereas it maximizes n for all other cases.
A limiting factor that affects all populations in similar ways, regardless of population size, is called aan. A dense population that is reduced in a density independent manner by some environmental factor s will be able to recover differently than would a sparse population. A group of organisms of the same species occupying a particular space at a particular time cole 1957. Explain how each can influence population growth density independent influences mortality in a population regardless of population at a given time affects growth rate and mortality. Population density is the number of individuals per unit area.
Explain how two critical factors influence whether a species will evolve toward semelparity or iteroparity. The importance of population growth and regulation in human. Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem. The populus help system beginning with populus release 5.
Experimental design and statistical analysis go hand in hand, and neither can be understood without the other. Various factors are employed to chart the population growth of species in order to ensure that it doesnt have any untoward effect on the ecosystem. Weakening density dependence from climate change and. Chapters 5 and 6 populations and humans in the biosphere.
If the statement is false, replace the italicized term or phrase to make it true. Eurycea ecology, behavior, and physiology crow, forstner, ostrand. With your group, discuss as many reason that you can think of that might be causing the sea otter population decline 6. Density independent factors, such as weather and climate, exert their influences on population size regardless of the populations density. Factors regulating population size are broadly classified into. Density dependent factors are more effective with a high density population and include food supply, disease, parasitism, competition. Population size and growth may also be controlled by density independent factors, e. If growth is limited by resources such as food, the exponential growth of the population begins to slow as. Densitydependent limiting factors cause a populations per capita growth rate to. Other articles where densityindependent factor is discussed. Density dependent factors have an increased effect on a population as population density increases. In contrast, the effects of density dependent factors.
Change in sea otter populations around the aleutian islands 4. Determining how intrinsic and extrinsic factors contribute to amphibian. The following are types of density independent factors. Some relationships between densityindependent selection and. Density independent and dependent factors effects on population. Density independent factors are limiting no matter what the size of the population. Introduction to population ecology radcliffes ipm world. A language and environment for statistical computing. Gotelli, 2001, a primer of ecology what is a population. The geographic range is the area in which a population lives. Pdf understanding population change is essential for conservation of imperiled species, such as. To be specific, both densitydependent selection and. The category of density independent limiting factors includes fires, natural disasters earthquakes, floods, tornados, and the effects of pollution. Pdf density dependence and independence researchgate.
Density independent and dependent factors effects on. A dense population that suffers mortality from a density independent cause will be able to recover differently than a sparse population. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Unusual weather such as hurricanes, droughts, or floods, and natural disasters such as wildfires, can act as density independent limiting factors. Only a small fraction of the myriad statistical analytic methods are covered in this book, but. Based on the textbook, biology, by miller and levine. Fw 662 lecture 1 densityindependent population models text. A comparison of densitydependent and densityindependent. Density independent factors are unrelated to population density.
The density independent factors tend to be abiotic. Abiotic factors include such things as temperature, humidity, rainfall, soil. Harry smith, pioneering biological control worker with the university of california 1935, proposed the equivalent and now accepted terms density dependent and density independent. Fw 662 lecture 1 densityindependent population models. Differentiate between density dependent and density independent factors. In truth, a better title for the course is experimental design and analysis, and that is the title of this book.
Ap biology reading guide julia keller 12d fred and theresa holtzclaw. Populations may be regulated by either density dependent factors, density independent factors, or both. Natural disasters such as droughts, floods, hurricanes, tornadoes, and fires can be devastating to any habitat no matter what size it is. Describe density independent and density dependent factors. What are density independent factors, and how do they affect population.
Effects of yersinia pestis on the human population. In reallife situations, population regulation is very complicated and density dependent and independent factors can interact. Density independent factors are limiting factors that affect all populations regardless of their densities whereas density dependent factors only affect populations when they reach a specific density. Influence of density dependent and densityindependent factors. If the roosevelt elk population is below k carrying capacity, i expect to find a stronger influence from density dependent factors on population dynamics than density independent factors.
Identify the following as either density dependent or density independent. This chapter addresses the roles of abiotic and biotic factors, and their. Brown, department of biology, university of new mexico, albuquerque, nm. We compare the two in a bid to find out what they are responsible for. Population and limiting factors background in nature, populations of organisms rarely grow uncontrolled. Compare and contrast density independent and density dependent regulation. Densityindependent regulation can be affected by factors that affect birth. Different populations may have very different age structures and these will determine their growth patterns. What are density independent factors, and how do they. An example of a density dependent variable is crowding and competition. Weakening density dependence from climate change and agricultural. Explain the effect of offspring care on parental survival in kestrels. Density independent factors limit population sizes in an ecosystem due to events that occur regardless of the density of a certain population. Density dependent mortality can be overcompensating, undercompensating or exactly compensating.
Estimating the strength of density dependence in the presence of. All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy. Density dependent factors density independent factors environmental resistance er population ecology a factor that causes higher mortality or reduced birth rates as a population becomes more dense is referred to as a density dependent factor. Pdf densitydependent and densityindependent drivers of.
Density independent mortality factors density independent factors determine population changes and set the stage for the existence of populations. The geometric or exponential growth of all populations is eventually curtailed by food availability, competition for other resources, predation, disease, or some other ecological factor. Density independent factors can affect a population no matter how many organisms are living in an area. This is the example youre most likely to see in your textbook. These determining factors are classified into density dependent and densityindependent factors. I also examined whether the influence of factors had a timelag of one or two years. Densitydependent and densityindependent population. How populations grow characteristics of populations.
Natural or manmade disasters can reduce population size, regardless of whether carrying capacity has been reached. Such as food, water, and space density independent factors are factors that the population density. Density independent factor biology with engelbrecht at. Negative feedback prevents unlimited population growth. This will improve the appearance of our help screens, and make future modifications much easier. Biology students who have a basic understanding of functions, specifically 9th and 10th. In population ecology, densitydependent processes occur when population growth rates are. Biology is brought to you with support from the amgen foundation. In population ecology, densitydependent processes occur when. Density independent factors, in ecology, refer to any influences on a populations birth or death rates, regardless of the population density. Small populations are particularly at risk of being wiped out by density independent limiting factors. There also exists densityindependent inhibition, where other factors such as weather or. Density dependent mortality factors are those that are facultative in effect, density independent mortality factors are those that are catastrophic in effect.
A variety of factors can cause negative feedback on population growth. Dandelions above and a lioness with cub inset 95 section 4. Density independent factors must reflect the periodic nature of the curve and cannot include cataclysmic events such as earthquakes, volcanoes, etc. Density dependent factors are primarily responsible for regulating populations about an average level of abundance. A population can also crash due to factors like depletion of resources, buildup of wastes and pollutants. Density independent factors affect all individuals in a population the same and may include physical factors such as climate, weather or salinity or catastrophic events such as floods, fires or drought. Biotic potential birth potential, capacity for survival, procreation, length of reproductive life carrying capacity depends on materials and energy, food chains, competition, density density dependent vs density independent factors. Density independent limiting factors cause abrupt and erratic shifts in population size. A limiting factor that only becomes limiting for a population when the population density reaches a certain level density independent limiting factor a limiting factor that affects all populations in similar ways regardless of population size and density ill focus on density independent. Adapted from holt biology 2008 chapter 5 section 1. How the individuals are spaced in their range is a populations distribution. Then state the specific limiting factor that is occurring. Density dependent and independent limiting factors.
1541 1451 1214 1103 767 916 404 1555 338 1476 1637 888 574 53 157 1114 392 519 1209 192 1234 758 518 514 345 1535 94 1178 869 629 1591 1391 1263 1396 1611 937 570 67 718 507 869 182 1433 614 1477 1377