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Biology 2 Chapter 45 Notes

by: Courtney Luber

Biology 2 Chapter 45 Notes BIOL 1040

Marketplace > Clemson University > Biology > BIOL 1040 > Biology 2 Chapter 45 Notes
Courtney Luber

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ALL of the notes from the chapter 45 powerpoint lectures
General Biology II
Dr. William Surver
Class Notes
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This 8 page Class Notes was uploaded by Courtney Luber on Thursday April 14, 2016. The Class Notes belongs to BIOL 1040 at Clemson University taught by Dr. William Surver in Fall 2016. Since its upload, it has received 16 views. For similar materials see General Biology II in Biology at Clemson University.


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Date Created: 04/14/16
Chapter 45 – Population and Community Ecology  Introduction o Population Ecology is concerned with  The changes in population size  Factors that regulate populations over time o Populations  Increase through birth and immigration to an area  Decrease through death and emigration out of an area o Population  A group of individuals of a single species that occupy the same general area  A group of individuals that share a common gene pool o Individuals in a population  Rely on the same resources  Are influenced by the same environmental factors  Are likely to interact and breed with each other o Population may be described by the number and distribution of individuals o Population dynamics – the interactions between the biotic and abiotic factors causes variation in population sizes o Human population problems  46.2 million living in poverty in US – below $27,000  Most resources are consumed by relatively few people in developed countries  Density and Distribution Patterns o Population density is the of individuals of a species per unit area or volume o Examples of population density  The number of oak trees per square kilometer in a forest  The number of earthworms per cubic meter in forest soil o Ecologists use a variety of sampling techniques to estimate population densities o The density of a population is not always easy to determine o Where to find information – how accurate?  Literature search  Demographic data o Animals move about so how can one be confident with density estimates; only able to sample a small area o Within a population’s geographic range, local densities may vary greatly o Some methods used are  Capture-recapture  Quadrants (sample plot method) o Assumptions in capture-recapture  Marking has no effect on mortality  Marking has no effect on the likelihood to being captured  There is no immigration or emigration between the sampling times  The dispersion pattern of a population refers to the way individuals are spaced within their area  Life Tables and Survivorship Curves o A life history pattern is a set of adaptations that influence survival, fertility, and the age at first reproduction o It is a set of conditions pertaining to an individual’s schedule of reproduction o Summarized in life tables and survivorship curves o Life table  Tracks age-specific patterns  Population is divided into age categories  Birth rates and mortality rates are calculated for each age category  Each species has a characteristic life span; not all achieve it o Ecologists use survivorship curves to plot a cohort’s age-specific survival in a habitat o Type I – high survivorship until fairly late in life, then a large increase in death; elephants and other large mammals; humans o Type II – reflect a fairly constant death rate at all ages; characteristic of lizards, small mammals, and large birds o Type III – death rate that is highest early on; species that produce many small offspring and do little, if any, parenting; invertebrates  Population Growth o Exponential growth model  The rate of a population increases under ideal conditions  Calculated using the equation G = rN  G is the growth rate of the population  N is the population size  r is the per capita rate of increase-the  average contribution of each individual to population growth birth rate – death/population size o carrying capacity levels off population growth  carrying capacity—what the environment can sustain o Logistic growth model is a description of idealized population growth that is slowed by limiting factors as the population size increases o G=rN ((K-N)/K) o K stands for the carrying capacity, the maximum population size a particular environment can sustain  Density Dependent Factors o Multiple factors may limit population growth o The logistic growth model predicts that population growth will slow and eventuall stop as population density increases o At higher populations densities density-dependent rates result in  Declining births and/or  Increase in deaths o Intraspecific competition (competition between same species) – compete for limited resources – food, nutrients, nesting sites o Limits growth in natural populations  Density Independent Factors o Factors unaffected by density – density independent o Natural disasters  Fires, storms  Habitat destruction  Seasonal changes in weather  Will occur regardless of population size o Some populations fluctuate in density with regularity (still at a specific carrying capacity) o Boom and bust cycles may be due to  Food shortages  Predator-prey interactions o Snowshoe hare and lynx populations based on the number of pelts sold by the Hudson Bay Company over a period or nearly 100 years. o What causes the boom-and-bust cycles of snowshoe hares?  When hares are abundant they overgraze their winter food supply resulting in high morality  Hare population cycles attributed by excessive predation o Using radio collars to track individual hares, it was determined that  90% of hares had been killed by predators and none had died of starvation  These results support the predation hypothesis  However, further experiments showed that although fluctuating food availability is not the primary factor controlling hare population cycles, it does play an important role  Climate Change – TED Talk o Al Gore o The sky is a very thin shell of atmosphere surrounding the planet o 110 million tons of greenhouse gases being spewed every day o We rely on carbon-based school for 85% of fossil fuels o Extremely hot days 150x more common than they were 30 years ago o Super storm Sandy 9 degrees warmer than average temperatures o As temp increases, oceans evaporate more moisture into sky o Moisture is pulled from ground—dry land; vegetation dies; prevalent fires o Zika virus – spreads in hot weather o People are beginning to use batteries, solar power, and wind power more and more o We CAN change o Many proposed US coal plants have been cancelled and many existing plants have been closed  Life Histories o Life history – the traits that affect an organism’s reproduction and death make up its life histories o Key life history traits include  Age of first reproduction  Frequency of reproduction  Number of offspring  Amount of parental care o Populations with r-selected life history  Found in disturbed or transitory environments  Have short life spans  Begin breeding early in life  Opportunistic  Short generation times  Produce large numbers of offspring o Populations with r-selected life history  Take little care of their offspring and infant mortality is high  Have efficient means of dispersal  Type III survivorship curve  Never reach K o Populations with k-selected life history  Usually found in stable environments  Have a long life span  Begin breeding later in life  Usually have long generation times  Most produce small numbers of offspring  Have parental care of their young o Populations with k-selected life history  Have a type I or II survivorship curve  Efficient in exploiting an ever-narrower slice of their environment  Tend to reach K  Applications o Sustainable resource management  Harvesting crops  Eliminating damage to a resource o Cod fishing off Newfoundland  Over fished, collapsed in 1992 and has not recovered o Resource managers use population ecology to determine sustainable yields  Human Population o The human population th  Grew rapidily during the 20 century and currently stands at over 7 billion o An imbalance between births and deaths is the cause of population growth (or decline) o The human population is expected to conitinue increasing for at least the next several decades o Growth rate is slowing o Demographic transition of a shift from zero population growth, in which birth rates and death rates are high buy roughly equal to zero population growth characterized by low but roughly equal birth and death rates o Mexico is expected to approach zero population growth with low birth and death rates in the next few decades o Developing nations  Death rates have dropped  Birth rates are still high  Populations are growing rapidly o Age structure  The proportion of individuals in different age groups  Affects the future growth of the population  Population momentum  Ecological Footprint o Is an estimate of the amount of land required to provide the raw materials an individual or a nation consumes  Food  Fuel  Water  Housing  Waste disposal o The United States  Has a very large footprint, much greater than its own land  Running on a large ecological deficit o Some researchers estimate that. if everyone on Earth had the same standard of living as people in the United States, we would need the resources of 4.5 planets  Community Ecology o Community ecology is concerned with factors that  Influence species composition and distribution of communities  Affect community stability o Community ecologists seek to understand how abiotic factors and interactions among populations affect the composition and distribution of communities o A biological community is  An assemblage of all the populations of organisms living close enough together for potential interaction  Describe by its species composition o The boundaries of a community vary with the research question investigated  A pond  The intestinal microbes of a pond organism o The place where an organism lives is its habitat o The habitat of an organism is characterized by physical and chemical features and the array of other species living in it o Directly or indirectly, the populations of all species in the habitat associate with one another as a community o What are some factors that shape community structure?  Climate and topography  Available foods and resources  Adaptations of species in community  Species interactions  Arrival and disappearances of species  Physical disturbances  Niche Concept o The niche concept  Niches are sometimes difficult to understand but in reality they are not  A niche is the sum of activities and relationships in which a species engages to secure and use resources necessary for survival and reproduction  Be sure that you can distinguish between a habitat and a niche  Habitat is you address and the niche is your occupation in that niche o Fundamental niche  Theoretical niche occupied in the absence of any competing species o Realized niche  The niche a species actually occupies  It is some fraction of the fundamental niche  Competition o Commensalism  One benefits other is not affected  Difficult to determine o Example-Remora and shark o Competition may be  Intraspecific and interspecific  Intraspecific is usually fiercer and has more several consequences..why is this so? o Gause in the 1930’s proposed the Principle of Competitive Exclusion  Competition occurs when niches overlap  The more overlap the greater the competition  Exclusion occurs when two niches completely overlap…but do they? o One way to avoid competition is to locate new resources within your niche-resource partitioning o Your niche then becomes slightly different than a competitor  Predator/Prey Interactions o Predator is the feeder, prey is the feed o Predators get their food from prey, but they do not take up residence on or in the prey (contrast to parasites) o Many of the adaptations of predators and their victims arose through coevolution o Prey do have defenses which protect them from predators  Camouflage  Warning coloration  Mimicry  Moment of truth defenses o Predator may respond through new adaptations  Ecological Succession o Communities come into being by ecological succession o Change in the composition of species over time o Classical model describes a predictable sequence with a stable climax community o Primary succession – new environments; bare rock succession o Secondary succession – communities were destroyed or displaced o Climax community  Stable array of species that persists relatively unchanged over time  Succession does not always move predictably toward a specific climax community, other stable communities may persist o The following slides show examples of succession


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