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Biology L101, Week 2 Notes

by: Megan

Biology L101, Week 2 Notes BIOL-L101

Marketplace > Indiana University South Bend > Biology > BIOL-L101 > Biology L101 Week 2 Notes

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These notes cover the topics of ecology, demography, life tables, exponential and logistic growth models, and life history.
Intro to Biological Sciences 1
Deborah marr
Class Notes
Biology, Science, demography, Ecology
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This 6 page Class Notes was uploaded by Megan on Saturday September 3, 2016. The Class Notes belongs to BIOL-L101 at Indiana University South Bend taught by Deborah marr in Fall 2016. Since its upload, it has received 6 views. For similar materials see Intro to Biological Sciences 1 in Biology at Indiana University South Bend.


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Date Created: 09/03/16
Biology Notes Chapter 52 (52.1-52.2) Ecology: study of how organisms interact with one another within their environment  Tries to understand the distribution and abundance of organisms  Levels of ecological study: o Organismal ecology  Look at adaptations made by the individuals in order to live successfully in a particular area  Organism: a life-form—a living entity made up of one or more cells o Population ecology  Look at the number and distribution of individuals in a population change over time  Population: group of individuals of the same species  Live in same area at the same time o Community ecology  Look at the nature of interactions between species, including the consequences from those interactions  Community: populations of different species interacting in one area o Ecosystem ecology  Looks at the process of nutrients and energy move among organisms and through the atmosphere, soil, and water  Ecosystem: all of the organisms in a particular area  Includes living and nonliving components o Abiotic: non-living  Have a limited set of physical conditions o Biotic: living  Interact with other organisms o Global ecology  Looks at the effects humans have on the biosphere  Biosphere: the thin zone surrounding Earth  Where life exists Order from smallest to largest: electron, atom, molecule, gene, cell, tissue, organ, organism, population, community, ecosystem, biosphere Conservation biology: tries to study, preserve, and restore threatened genetic diversity in populations, species diversity in communities, and ecosystem function Chapter 54 Biogeography: how organisms are distributed geographically  Range: also known as graphic distribution (of species) o In constant flux as biotic and abiotic factors change over time Population density: number of individuals per unit of area  Organisms can be arranged if the following different patterns: o Random  Each individual is positioned independent from the others o Clumped  Patchy habitat, organisms associate in social groups o Uniform  Negative interactions among individuals (ex. Competition for space, water, other resources) Metapopulation: population of populations connected to migration  Humans changing organism habitats into reserves causes more and more species to become part of the metapopulation structure Demography: number of individuals present in a population, depending on the processes of birth, death, immigration, and emigration  Population increase: caused by birth and immigration o Immigration: individuals entering a population by moving from another  Population decrease: caused by death and emigration o Emigration: individuals leave a population to join another  In order to predict the future of a population, the age structure must be known along with how likely individuals at each age will survive, offspring produced, and how many individuals immigrate or emigrate each generation o Age structure: how many individuals of each age are alive o Generation: average time between the mother’s first offspring and her daughter’s first offspring Life table: used to summarize the probability that individuals will survive and reproduce in any given time interval over its lifetime  Biologists often focus on females when calculating data for the table because males rarely affect population growth  Types of life tables: o Static life table: made from age structure of population at a specific point in time  Age class (x)  Group of individuals of a certain age  Number of survivors (Nx)  Individuals that survived to reach the current age class  These individuals are known as a cohort which is a group of the same age that can be followed through time  Survivorship (l x  The proportion of offspring (on average) produced that survived to a particular age  Mortality (q x  Mortality rate = death rate  Life expectancy (e )x  The average time the organisms in a group are going to live o Cohort life table: track cohort over their lifetime  Survivorship (l x: see above  Mortality rates for age class (q x: see above  Life expectancy: see above  Reproduction (m ) x  Average number of offspring produced by each female in an age class o Also known as fecundity  Reproductive rate per age class (l mx) x  Probability of survival and reproduction at an age class  Net reproductive rate (R =0sum of l m x x  Average number of offspring produced by an individual over its lifetime  Indicates whether the population is increasing or decreasing o Estimate population size of the following generation  R 0 1 : population stays the same  R > 1 : population increases 0  R 0 1 : population decreases  Survivorship curve o Y-axis: log10N x o X-axis: age o There are three types of survivorship curves  Type 1  Survivorship throughout life is high  Most individuals approach the maximum life span of their species  Organisms with this curve often have more parental care than other types o Example: humans  Type 2  Organisms have about the same probability of dying each year o Example: many types of birds  Type 3  Extremely high death rates early in life, but higher survival rate later in life o Example: trees (not many seedlings become trees) Type 1 Type 2 Type Intrinsic rate of increase (r): instantaneous population growth rate  r = birth rate – death rate o r = 0 : population stays the same o r > 0 : population increases o r < 0 : population decreases Exponential growth model (J-shaped)  Nt= N e0 rt o Nt= future population size o N0= initial population size o e = a constant  Irrational number x  Approximately 2.72 but look on your calculator for the “e ” button  Taking the natural log (ln) of both sides cancels out this constant when looking for r or t o r = rate of increase o t = time  Doubling time = (ln2)/r  Assumptions of exponential growth model: o Stable environment/resources stay same (food, disease, etc.) o Birth/death rates constant o Age structure stays the same Logistic growth model (S-shaped)  Population is unable to grow infinitely large o The limitation of resources affect the population growth rate  dN/dt = rN x ((K-N)/K) o dN = difference in number of individuals o dt = change in time o r = rate of increase o N = number of individuals o K = carrying capacity  Maximum number of individuals of a population that can be supported by a certain habitat without reducing the ability to support the same species in the future  This can vary over time and between populations  Depends on:  Number of organisms  Lifestyle (how many resources)  Environment  Population is growing the fastest at half of the carrying capacity  Maximum sustainable yield = K/2  Assumptions of logistic growth model: o Constant K o Immigration and emigration rates remain constant o Population immediately responds to limiting factors o Stable age distribution o There is no change in genetic structure of the population  Life history: how an individual distributes resources to growth, reproduction, and activities related to survival o Almost all cases show this is shaped by natural selection that maximizes an individual’s fitness in its environment o Life cycle characteristics include:  Speed at which the organisms will grow  Number of times the organism reproduces  Number of offspring  Sex ratio  The life span and survivorship patterns  The amount of time spent in the pre-reproductive, reproductive, and post-productive stage o Types of life histories  Lifespan  Annual organisms o Generations do not overlap o Examples: some plants and insects  Perennial organisms o Overlapping generations o Examples: fungi, mammals, amphibians, birds  Reproduction  Semelparity o Big bang reproduction o Can be either annual or perennial o Example: squid, mayflies, salmon, bamboo  Iteroparity o Repeated reproduction o Usually perennial o Example: mammals, trees, birds


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