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February 4th

by: Sierra

February 4th Biol 28600


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Notes from February 4th
Introduction to Ecology and Evolution
Joshua Springer
Class Notes
Ecology, evolution, Biology
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This 53 page Class Notes was uploaded by Sierra on Thursday February 11, 2016. The Class Notes belongs to Biol 28600 at Purdue University taught by Joshua Springer in Spring 2016. Since its upload, it has received 29 views. For similar materials see Introduction to Ecology and Evolution in Biology at Purdue University.


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Date Created: 02/11/16
Exam I Locations for Monday 15 February 8:00—10:00pm  Last/Surname begins with O—Z  Go to WTHR 200  PLUS those with accommodations that are NOT going to the DRC to take the test  Last/Surname begins with A—N  Go to EE 129  You MUST show your student ID when you turn in your exam!  No lecture on Tuesday, Feb 16 = Compensation Day Properties of Populations  A population is a group of individuals of the same species that inhabit a given area  Populations have structure, including density, spacing and age distribution  Populations are dynamic, changing over time  Why is it important that the individuals are members of the same species?  Why is it important for a population to have a spatial boundary?  Human construct sometimes (we determine boundaries based on our studies) Organisms May Be Unitary or Modular  Suckers – new stems that sprout from surface roots and may appear to be individuals  Genet – plant produced by sexual reproduction, a genetically unique individual  Ramet – module produced asexually by a genet (these are essentially clones) Many species such as Aspens (Populus spp.) exhibit this trait Clones Parent (c) Pando! (Quaking Aspen in Utah)  iClicker Which of the following is not a resource that could be used by a tree? A) Water in the soil B) Temperature C) Carbon Dioxide in the atmosphere D) Nitrogen E) Potassium Figure 8.5 Geographic Range of a species; Red Maple, Acer rubrum 0 200 400 600 kilometers The Distribution of a Population Defines Its Spatial Location  Ubiquitous species have a geographically widespread distribution  Endemic species have a geographically restricted distribution  many endemic species have specialized habitat requirements  the shale-barren evening primrose is found only on hot, shale-barren environments, on south or southwest facing slopes in the Allegheny Mountains The Distribution of a Population Defines Its Spatial Location  There are many types of geographic barriers that reduce or prevent individuals from moving and colonizing new areas  bodies of water, including rivers  mountains  large areas of unsuitable habitat such as deserts  Interactions with other species can also serve as barriers  competition  predation Figure 8.7 Continental Worldwide Ocean River Physiographic Cluster area Region Pine barrens Coniferous stump 4000 Swampy 20' clay bank 400 N Stream 100 10,000 Locality Colony 8500 Clump The Distribution of a Population Defines Its Spatial Location  The environment is heterogeneous  thus most populations are divided into subpopulations that live in suitable habitat patches surrounded by unsuitable habitat  A metapopulation is the collection of these local subpopulations  These subpopulations are spatially separated but connected by the movement of individuals between them (migration!) Figure 8.8 (a) Mountain sheep (b) (Ovis canadensis) Abundance Reflects Population Density and Distribution  Abundance is a function of population density and the area over which the population is distributed  Crude density  the number of individuals per unit area  square meter (m ), square kilometer (km )  Or the number of individuals per unit volume  kiloliter (m ) or liter (.001 m )  Place a grid over a population distribution and calculate the density for a given grid cell  WE NEVER REALLY WANT TO USE THE U.S. SYSTEM OF MEASUREMENT; IT’S TERRIBLE! Figure 8.9 Why is this not always an accurate way to determine density? 3 2 1 Figure 8.10a (a) Random Figure 8.10b (b) Uniform Figure 8.10c (c) Clumped This is the most common spatial distribution and results from a number of factors -suitable habitat or resources are found in patches -species form social groups (herds, flocks, schools) -ramets formed by asexual reproduction Abundance Reflects Population Density and Distribution  Spatial distributions of individuals may be described at multiple spatial scales  In the savanna ecosystems of Southern Africa  the shrub Euclea divinorum has a clumped distribution  the clumps occur because Euclea grows under the canopy cover provided by Acacia tortilis trees  the clumps are uniformly spaced because Acacia trees have a uniform distribution due to competition between individual trees for water Figure 8.11 (a) 20 m 20 m Acacia tortilis Euclea divinorum (b) Abundance Reflects Population Density and Distribution  To account for the patch distributions of some species, ecologists may use  Ecological density – the number of individuals per unit of available living space  bobwhite quail prefer hedgerow habitat  density can be expressed as number of birds per mile of hedgerow rather than birds per hectare  However, it can be difficult to determine what part of a habitat is living space for a particular species Determining Density Requires Sampling  Population size (abundance)  population density  the area occupied  How is density determined?  Do some techniques work better then others for organisms with certain characteristics, for example, mobile versus sessile? Figure 8.13 Determining Density Requires Sampling  How accurate is this method?  Depends largely on the spatial distribution of individuals in the population  works well if individuals have a uniform distribution  works less well with a random or clumped distribution  important to report a confidence interval or some estimate of variation = statistics!  Can also be influenced by the choice of boundaries or sample units Determining Density Requires Sampling  Mark-recapture is the most commonly used technique to measure animal population size  This method is based on  capturing a number of individuals in a population  marking them with a mark that will not be lost during the course of the study  releasing a known number of marked individuals (M) back into the population (N  the value being estimated)  after an appropriate period of time, recapture a number of individuals in the population Figure 8.15 Determining Density Requires Sampling  Of the individuals captured the second time (n), some will have been marked, or recaptured (R)  To estimate the population density:  Assume that the ratio of n/R represents the ratio for the entire population (N/M)  N/M  n/R  Since N is the only unknown, rearrange the equation to solve for it:  N  nM/R Determining Density Requires Sampling  You are estimating the population density of the Northern Cardinals (Cardinalis cardinalis) in Tippecanoe County, Indiana. Your research team initially captures and bands 285 birds. Three months later, you return and capture 335 birds. Of those, 4 were banded on your previous trip. What is the estimated size of this N. C. population?  M  285, n  335, R  4  N  nM/R  [(335  285)/4]  25,294 You are part of a team studying an endangered species of land snail in upstate New York. You and your colleagues capture and mark 80 snails by putting a small spot of white paint on their shells. When you return five months later, you capture 45 snails and 5 of them have the mark. Based on these data, you conclude that the population of land snails has about ________________ individuals. A. 80 B. 128 C. 720 D. 2000 Determining Density Requires Sampling  Signs of the presence of animals include:  counts of vocalization, such as bird song  counts of animal scat seen along a certain length of trail  counts of animal tracks, such as footprints in the snow Measures of Population Structure Include Age, Developmental Stage, and Size  Abundance does not provide any information on the characteristics of individuals within a population  Why do populations with overlapping generations have an age structure?  What can the population’s age structure tell you about the growth of the population? Measures of Population Structure Include Age, Developmental Stage, and Size  A population with non-overlapping generations does not have an age structure  individuals reproduce and die within a single season  annual plants and some insects  A population with overlapping generations has an age structure  there are individuals in different age classes  reproduction is restricted to certain age classes  mortality is more common in certain age classes Measures of Population Structure Include Age, Developmental Stage, and Size  Populations can be divided into three ecologically important age classes  prereproductive  reproductive  postreproductive  How long an individual is in each age class depends on the organism’s life history  some organisms, such as mice, have a very short span of time between generations  other organisms, such as elephants, have a very long span of time between generations Measures of Population Structure Include Age, Developmental Stage, and Size  The most accurate method is to mark young individuals in a population and follow their survival through time  This is also the most difficult  many individuals must be marked and subsequently checked at regular intervals, often over many years Measures of Population Structure Include Age, Developmental Stage, and Size  Less accurate methods include  Examining a sample of bodies of individuals that have died and determine their ages at death  Look for characteristics that indicate age  wear and replacement of teeth  growth rings in the teeth or horns  plumage changes and wear in birds  annual growth rings on scales and ear bones in fish Figure 8.16 Adult Juvenile Adult Juvenile (a) (b) Adult Juvenile Neonatal Juvenile Adult (c) (d) Measures of Population Structure Include Age, Developmental Stage, and Size  It can be more challenging to estimate age structure in plants  Trees with seasonal growth produce annual growth rings  Dendrochronology – counting annual growth rings to determine the age of a tree  Size of the tree based on diameter at breast height (dbh) can also be used  however, growth conditions can strongly affect this measurement Figure 8.17 (a) 0.8 0.6 0.4 Radial increment (cm) 1989 1980 1970 1960 1950 1940 1930 1920 Year (b) Figure 8.18 An age pyramid is a graphical representation of the age structure of a population Age Male Female Male Female Male Female 80+ 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 Under 5 8 6 4 2 0 2 4 6 8 6 4 2 0 2 4 6 6 4 2 0 2 4 6 Percentage of population Percentage of population Percentage of population (a) Egypt (b) United States (c) Japan Figure 8.19 50 40 30 20 10 Percentage of population 0 10 20 30 40 50 60 70 80 90 100 110 120 Age (years) Sex Ratios in Populations May Shift with Age  In most mammalian populations, the sex ratio at birth (secondary sex ratio) is slightly weighted towards males (estimated at 107 males/100 females, or 1.07:1 for humans)  the sex ratio shifts towards females in older age classes  males generally have a shorter life span than females  many species are characterized by rivalries among males for resources or mates Sex Ratios in Populations May Shift with Age  In birds, the number of males tends to be higher than females  nesting females are more susceptible to attack and predation Individuals Move within the Population  Dispersal is the movement of individuals in space  Generally implies the movement of individuals away from one another  emigration – when individuals leave a subpopulation  immigration – when individuals enter a subpopulation  Movement of individuals between subpopulations is an important part of metapopulation dynamics  maintains gene flow between the subpopulations Section 8.7 Individuals Move within the Population  Migration is movement of organisms that is round- trip. These trips may be daily or seasonal:  zooplankton move in the water column; lower depths during the day and the surface at night  bats leave caves at dusk, move to feeding areas, then return at dawn  earthworms move deep into the soil for winter to avoid freezing, then move back up in the spring  gray whales feed in the Arctic during the summer, winter off the California coast where calves are born Figure 8.23 (b) (a) Winter breeding grounds Population Distribution and Density Change in Both Time and Space  Dispersal can affect the spatial distribution of individuals within a population.  emigration leads to a decline in density  immigration leads to an increase in density, or can establish a new subpopulation in a previously unoccupied habitat  Species introduced into an area where they did not previously live can expand into new areas  These introductions may be intentional or unintentional Figure 8.24 Gypsy Moth (Lymantria dispar) spread in the United States 1900 1934 1967 1994 2012 Annual economic losses are approximately $868 million Figure 8.27 (a) (b) Ecological Issues & Applications: Humans Aid in the Dispersal of Many Species, Expanding Their Geographic Range  Dispersal by humans has led to the redistribution of species on a global scale  Invasive species – organisms successfully introduced to places they have never occurred  freed from the constraints presented by their predators, parasites, and competitors in their native range, many species have become established and spread  Sometimes the introduced species are harmless, but more often they have negative effects on native species and ecosystems Ecological Issues & Applications: Humans Aid in the Dispersal of Many Species, Expanding Their Geographic Range  Unintentional introductions often happen through the importation of agricultural and forest products  weed seeds may be included in a shipment of crop seeds or carried in the fur or feathers of domestic animals  soil carrying seeds is used as ballast in a ship, then dumped in another country when cargo is picked up  major forest insect pests have come in through wooden shipping containers and pallets Ecological Issues & Applications: Humans Aid in the Dispersal of Many Species, Expanding Their Geographic Range  Humans have intentionally introduced nonnative plants for ornamental and agricultural purposes  There are many examples of this in North America  purple loosestrife – introduced from Europe, it has spread into wetlands, eliminating native plants  Australian paperbark tree – introduced as an ornamental plant in Florida, it has displaced many native species  kudzu – an ornamental vine that has spread throughout the southern United States, outcompeting other plants Figure 8.26 (a) (b) Ecological Issues & Applications: Humans Aid in the Dispersal of Many Species, Expanding Their Geographic Range  Aquatic environments have also been affected  More than 139 nonnative aquatic species have invaded the Great Lakes through shipping  the zebra mussel is native to the lakes of southern Russia and was introduced in ballast water  it is now found in most eastern rivers and the Great Lakes  The San Francisco Bay Area has 96 nonnative invertebrate species  Introduced exotic fish are responsible for 68 percent of recent fish extinctions in North America Asian Carp!


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