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4.3: Lab Assignment 4: Population Monitoring and Field Sampling - Biology


Name: ________________________________

Sampling for pests only provides useful estimates of population size when two important aspects are addressed: accuracy and precision. Accuracy is how close your sampling is able to reflect actual population size. Precision is when the data collected in each sampling event are relatively equal, with little or no variation. When precision is poor, more samples are required to generate more accurate data.

Determining sample size: Rarefaction Curves

With each sampling event, we gain more information about our ecosystem. In the example below, you’ll be filling in Table 1 with the values given using Appendix A, which is a data set built on number of insects recorded during scouting.

Sample No.# Species in SampleTotal NEW SpeciesTOTAL SPECIES (Cumulative)
1
2
3
4
5

Table 1.

Using your data, extrapolate the results to reflect a hypothetical organic garden that when considered as a whole, is comprised of 150 plots of the same size.

For example:

  • If there were a total of 40 individuals sampled, and 10 are pest species A, then species A is 25% of the population (10/40 = .25). This percentage is the relative abundance.
  • 25% of 150 (150×25) is 37.5, so we assume that in the entire production area, there should be about 38 (rounding to the whole insect) species A individuals.
Species No.Species NameTotal No. Sampled (cumulative)Relative Abundance (%)Extrapolated Abundance (x30)

Table 2.

Now add the data from the next 5 samples (samples 6-10), adding to your counts, in the table below.

Sample No.# Species in SampleTotal NEW Species (including prev. samples)Total Cumulative Species
6
7
8
9
10

Table 3.

With the new data, you’ll need to recalculate the relative and total abundance for each species identified over 10 sampling events.

Species No.Species NameTotal No. Sampled (cumulative)Relative Abundance (%)Extrapolated Abundance (x15)

Table 4.

Was there a difference in the number of the species between table 1 and table 3? Is the changing number of species an indication of changing accuracy or precision?

Was there a difference in the overall relative abundances for each species? Why/Why not?

Plot your data on the graph below, showing the total number of species found as a response to the number of samples taken by highlighting the cells in the table at each data point. Because we are tracking cumulative data, connect the data points with a line of highlighted cells

The plot you have just created above is what is known as a rarefaction curve. This helps consultants and scientists monitoring populations of organisms select the correct sampling effort (number of sampling events or number of units sampled) that will cost the least amount of resources while still gaining accurate data for estimating population sizes. This point happens when there is little NEW information gained by additional sampling. Indicate where this occurs on your graph by adding a STAR at this point.

According to the graph you made, what is the ideal number of samples that should be taken to both minimize sampling effort while gaining the most information to accurately estimate populations?

Application.

In production systems, we don’t have the actual pest population sizes to compare with our samples, thus ensuring accuracy. Instead, we rely on repeated sampling efforts and a variety of sampling techniques to get information about the pest populations present.

Next, you will use a hypothetical sampling plot where you will conduct THREE different types of samples. Each sampling method is commonly used, but each gives very different types of information. For each sampling method, assume you know nothing about the data found by the two other techniques: complete each technique one at a time, ignoring previous sampling results. Using the Practice Plot PDF (separate file), fill in the sampling card for each technique.

I. Presence/Absence Sample Card

Sample every plant in the row to fill out the table below. Only mark if the pest is present by placing an “X” in the column if the species appears.

Species:Species:Species:Species:
PLANT No.(describe)(describe)(describe)(describe)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

With P/A sampling, the intent is to get an idea of the pests present in the system by searching every without making hourly cost of scouts increase by requiring a count of each population. When do you think this kind of sampling is the most useful and economical for growers?

II. Fixed Random Sample Card

Look at your plot and mentally overlay a 3×3 grid that covers the entire plot of available plants (see diagram on the right). Determine which end of the practice plot contains units 1-3 and which has 7-9. Determine which plant is the closest to the center of each sample unit in your plot. Examine these nine plants closely and fill out the sample card below, adding a new row in each plot when there are more than one “species” of pest found.

Grid Unit No.Pest(s)DescriptionNumberTotal Cumulative
ExampleLight GreenLight green +99
Dark greenLarge, round circle110
1
2
3
4
5
6
7
8
9

As you experienced, this type of sampling takes more time per plant, hence the need to reduce the number of plants sampled. Think about the first part of this activity, accuracy and precision and give one benefit and one drawback of using this type of sampling compared to the simpler Presence/Absence sampling event used for the previous sample card.

III. Sequential Sampling Card

Use the same nine plants identified in Sample Type II above. Check each plant for the light green “+”; if present, that plant is added to the tally as “1”. Each positive result adds to the running tally in the vertical column titled “your tally”. This column is additive– if the first three plants are all positive for the pest, then by the 3rdplant, there should be a “3” in the tally column. If plants 1 and 2 are positive, but 3 is negative, then there will still be a “2” in the tally column at the third plant.

Example:

Plant No.Pest Present?Don’t TreatYOUR TALLYTreat
1Yes1
2Yes2
3No223
4Yes233
5No234

Compare your count to the “Treat” and “Don’t Treat” recommendation columns to determine if pesticide management is necessary.

Plant No.Pest Present?Don’t TreatYOUR TALLYTreat
1
2
323
423
524
634
735
836
946
1047

For your nine plants, what is the recommendation for pest management?

Perform the sequential sampling a few times using different sampling patterns – one whole row, every other plant, ALL plants, etc. Did you consistently get the same pest management recommendation? Why/Why not?

What are the benefits and drawbacks of sequential sampling? When (in a production year/cycle) would this be the most useful means of sampling pests?

Wrap-Up Analysis

Insect identification is an important part of scouting for pests, especially when it comes to determining the difference between pests and similar-looking beneficial insects. However, training in identification for scouting jobs varies widely, which means there may not always be consistency in pest recognition and identification.

How do inconsistencies in identification change the precision and accuracy of each sampling type and analysis we’ve considered in this exercise?


1.4.8.B Types of Writing - Write multi-paragraph informational pieces (e.g., letters, descriptions, reports, instructions, essays, articles, interviews). (PA State Standard Reading, Writing, Speaking, and Listening)

1.4.8.C Types of Writing - Write persuasive pieces. (PA State Standard Reading, Writing, Speaking, and Listening)

1.5.8.A Quality of Writing - Write with a sharp, distinct focus. (PA State Standard Reading, Writing, Speaking, and Listening)

1.5.8.B Quality of Writing - Write using well-developed content appropriate for the topic. (PA State Standard Reading, Writing, Speaking, and Listening)

2.2.8.A Computation and Estimation - Complete calculations by applying the order of operations. (PA State Standard Mathematics)

2.2.8.B Computation and Estimation - Add, subtract, multiply and divide different kinds and forms of rational numbers including integers, decimal fractions, percents and proper and improper fractions. (PA State Standard Mathematics)

4.3.7.C Environmental Health - Explain biological diversity. (PA State Standard Environment and Ecology)

4.8.7.D Humans and the Environment - Explain the importance of maintaining the natural resources at the local, state, and national levels. (PA State Standard Environment and Ecology)

4.9.7.A Environmental Laws and Regulations - Explain the role of environmental laws and regulations. (PA State Standard Environment and Ecology)


Abstract

Biodiversity is under threat worldwide. Over the past decade, the field of population genomics has developed across nonmodel organisms, and the results of this research have begun to be applied in conservation and management of wildlife species. Genomics tools can provide precise estimates of basic features of wildlife populations, such as effective population size, inbreeding, demographic history and population structure, that are critical for conservation efforts. Moreover, population genomics studies can identify particular genetic loci and variants responsible for inbreeding depression or adaptation to changing environments, allowing for conservation efforts to estimate the capacity of populations to evolve and adapt in response to environmental change and to manage for adaptive variation. While connections from basic research to applied wildlife conservation have been slow to develop, these connections are increasingly strengthening. Here we review the primary areas in which population genomics approaches can be applied to wildlife conservation and management, highlight examples of how they have been used, and provide recommendations for building on the progress that has been made in this field.


Probability sampling methods

Probability sampling means that every member of the population has a chance of being selected. It is mainly used in quantitative research. If you want to produce results that are representative of the whole population, probability sampling techniques are the most valid choice.

There are four main types of probability sample.

1. Simple random sampling

In a simple random sample, every member of the population has an equal chance of being selected. Your sampling frame should include the whole population.

To conduct this type of sampling, you can use tools like random number generators or other techniques that are based entirely on chance.

Example

You want to select a simple random sample of 100 employees of Company X. You assign a number to every employee in the company database from 1 to 1000, and use a random number generator to select 100 numbers.

2. Systematic sampling

Systematic sampling is similar to simple random sampling, but it is usually slightly easier to conduct. Every member of the population is listed with a number, but instead of randomly generating numbers, individuals are chosen at regular intervals.

Example

All employees of the company are listed in alphabetical order. From the first 10 numbers, you randomly select a starting point: number 6. From number 6 onwards, every 10th person on the list is selected (6, 16, 26, 36, and so on), and you end up with a sample of 100 people.

If you use this technique, it is important to make sure that there is no hidden pattern in the list that might skew the sample. For example, if the HR database groups employees by team, and team members are listed in order of seniority, there is a risk that your interval might skip over people in junior roles, resulting in a sample that is skewed towards senior employees.

3. Stratified sampling

Stratified sampling involves dividing the population into subpopulations that may differ in important ways. It allows you draw more precise conclusions by ensuring that every subgroup is properly represented in the sample.

To use this sampling method, you divide the population into subgroups (called strata) based on the relevant characteristic (e.g. gender, age range, income bracket, job role).

Based on the overall proportions of the population, you calculate how many people should be sampled from each subgroup. Then you use random or systematic sampling to select a sample from each subgroup.

Example

The company has 800 female employees and 200 male employees. You want to ensure that the sample reflects the gender balance of the company, so you sort the population into two strata based on gender. Then you use random sampling on each group, selecting 80 women and 20 men, which gives you a representative sample of 100 people.

4. Cluster sampling

Cluster sampling also involves dividing the population into subgroups, but each subgroup should have similar characteristics to the whole sample. Instead of sampling individuals from each subgroup, you randomly select entire subgroups.

If it is practically possible, you might include every individual from each sampled cluster. If the clusters themselves are large, you can also sample individuals from within each cluster using one of the techniques above.

This method is good for dealing with large and dispersed populations, but there is more risk of error in the sample, as there could be substantial differences between clusters. It’s difficult to guarantee that the sampled clusters are really representative of the whole population.

Example

The company has offices in 10 cities across the country (all with roughly the same number of employees in similar roles). You don’t have the capacity to travel to every office to collect your data, so you use random sampling to select 3 offices – these are your clusters.

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Courses with the SOE Subject

The online catalog includes the most recent changes to courses and degree requirements that have been approved by the Faculty Senate, including changes that are not yet effective. Courses showing two entries of the same number indicate that the course information is changing. The most recently approved version is shown first, followed by the older version, in gray, with its last-effective term preceding the course title. Courses shown in gray with only one entry of the course number are being discontinued. Course offerings by term can be accessed by clicking on the term links when viewing a specific campus catalog.

School Of The Environment (SOE)

100 An Introduction to Our Environment: Geology, Ecology, and Environmental Stewardship 1 A holistic understanding of the Earth's environment knowledge of geology, ecology, environmental science, and human political dimensions basic comprehension of environmental issues.

101 [PSCI] Welcome to the Earth: An Introduction to Geology 4 (3-3) Course Prerequisite: Enrollment not allowed if credit already earned for SOE 102. Introductory physical geology for non-science majors emphasis on western US. Credit not granted for both SOE 101 and 102.

101 (Effective through Summer 2021) [PSCI] Introduction to Geology 4 (3-3) Course Prerequisite: Enrollment not allowed if credit already earned for SOE 102. Introductory physical geology for non-science majors emphasis on western US. Credit not granted for both SOE 101 and 102.

102 Geology for Science Majors 4 (3-3) Course Prerequisite: MATH 103, 106, 140, 171, 201, or 202, or concurrent enrollment in any of these, or a minimum ALEKS math placement score of 40%. Enrollment not allowed if credit already earned for SOE 101. Modern concepts of earth science mineral rock, resource, and map study. Field trip required. Credit not granted for both SOE 101 and 102.

102 (Effective through Summer 2021) Physical Geology 4 (3-3) Course Prerequisite: MATH 103, 106, 140, 171, 201, or 202, or concurrent enrollment in any of these, or a minimum ALEKS math placement score of 40%. Enrollment not allowed if credit already earned for SOE 101. Modern concepts of earth science mineral rock, resource, and map study. Field trip required. Credit not granted for both SOE 101 and 102.

103 [PSCI] Other Worlds: Comparative Planetology of our Solar System 3 Study of the geological processes and environments on planets and moons of our solar system.

105 [PSCI] Natural Resources and Natural Hazards 3 Survey of key natural resources, the physical processes by which nature and society produce those resources, and the processes of related natural hazards. Recommended Preparation: MATH 103 or higher with a C or better, or a minimum ALEKS math placement score of 45%.

110 [BSCI] The Environment, Human Life, and Sustainability 4 (3-3) Interactions between humans and their environment multidisciplinary introduction to environmental concepts and concerns.

204 Field Methods for Careers in the Natural Sciences 4 (3-3) Introduction to basic concepts, field techniques and the use of spreadsheets in natural resources. Field trips required.

204 (Effective through Summer 2021) Introduction to Measurements and Analysis in Natural Resource Sciences 2 (1-3) Introduction to basic concepts, field techniques and the use of spreadsheets in natural resources. Field trips required.

207 Geology Field Camp 3 (0-9) Course Prerequisite: SOE 101 or 102 SOE 210. Introduction to geologic field methods basic geologic mapping.

210 [PSCI] Earth's History and Evolution 4 (3-3) Introduction to earth's history and evolution through observations, data collection and analysis, readings and writing exercises.

210 (Effective through Summer 2021) [PSCI] Earth's History and Evolution 4 (3-3) Introduction to earth's history and evolution through observations, data collection and analysis, readings and writing exercises. Two field trips required.

230 [PSCI] Introductory Oceanography 3 Interdisciplinary study of ocean systems: marine geology, chemistry, physics and biology oceans' influence on climate and response to human activity.

250 [PSCI] Introduction to Earth System Science 3 Course Prerequisite: SOE 110 or BIOLOGY 106, each with a C or better. Earth's fundamental systems (the geo-, atmo-, hydro-, and bio-spheres) in the context of global change. Recommended: CHEM 101 or 105.

275 Rivers: Form, Function, and Management 3 Introduction to rivers, stream ecology, and restoration.

275 (Effective through Summer 2021) Rivers: Form, Function, and Management 3 Introduction to rivers, stream ecology, and restoration.

280 [PSCI] How the Earth's Climate System Works 3 Understanding how the Earth's climate system works to provide a scientific foundation for making informed evaluations about management and policy.

285 The Science and Policy of Climate Change 3 Course Prerequisite: SOE 110. The science of the climate system the case for reducing greenhouse gas emissions, and the best policies to do so.

300 Natural Resource Ecology 3 Ecology as applied to management of natural resource ecosystems biological diversity, conservation biology, global climate change in natural resource ecology. Field trips required.

301 Forest Plants and Ecosystems 3 (2-3) Course Prerequisite: SOE 300 or BIOLOGY 372 or concurrent enrollment in either. Identification and ecology of forest plants with emphasis on trees and the ecosystems in which they occur. Field trips required.

302 Arid Land Plants and Ecosystems 3 (2-3) Course Prerequisite: SOE 300 or BIOLOGY 372 SOE 301. Identification and ecology of arid land plants (trees, shrubs, grasses, forbs) and the ecosystems in which they occur. Field trips required.

303 Environmental Geology 3 Course Prerequisite: SOE 101 or 102. Geological hazards and geologic problems associated with human activities. Required field trip.

304 Ecosystem Field Measurements 4 (3-3) Course Prerequisite: SOE 204 SOE 300 or BIOLOGY 372 or concurrent enrollment in either SOE 301 or concurrent enrollment. Measurement and analysis of forests, wildlife habitat, and rangelands using field equipment and spatial sampling techniques development of employment skills in forestry, forest restoration, and wildlife management.

304 (Effective through Summer 2021) Ecosystem Field Measurements 4 (3-3) Course Prerequisite: SOE 204 SOE 300 or BIOLOGY 372 or concurrent enrollment in either SOE 301 or concurrent enrollment. Fixed-area sampling and analytical techniques for assessing various ecological variables and wildlife habitat variable radius sampling methods for forests and biomass estimation procedures for ecosystems.

305 Silviculture 3 Course Prerequisite: SOE 204 SOE 300 or BIOLOGY 372 SOE 301. Stand dynamics, natural regeneration methods, intermediate stand treatment, relationships of natural resource management to silvicultural practice. Field trips required.

306 Plants in the Environment 3 Course Prerequisite: SOE 300. How plants interact with their physical and biotic environments physiological function of plant acclimation, adaptation, and tolerance with emphasis on forests and trees.

306 (Effective through Summer 2021) Plants in the Environment 3 How plants interact with their physical and biotic environments physiological function of plant acclimation, adaptation, and tolerance with emphasis on forests and trees.

310 Methods in Wildlife Ecology 4 (3-3) Course Prerequisite: BIOLOGY 106 with a C or better. Field and laboratory sampling techniques in wildlife research and management.

311 Modeling the Environment 4 (3-3) Construction and testing of computer simulation models of environmental systems. Cooperative: Open to UI degree-seeking students.

312 [DIVR] Natural Resources, Society, and the Environment 3 Social views of natural resources processes by which these views are developed and expressed social conflict over natural resources.

314 Service Learning in Ecuador: Building Sustainable Local Solutions for Human and Environmental Health 3 Experience working alongside local communities in Ecuador on projects that will improve rural access to sustainable energy, clean water, improved ecosystem health, and sustainable livelihoods. Spring break field trip required.

315 Water and the Earth 3 (2-3) Course Prerequisite: CHEM 102 or 106 one of MATH 108, 140, 171, 172, 182, 201, 202, or ENGR 107 one of SOE 101, SOE 102, 4 credits PHYSICS 101 or 201, or PHYSICS 101 and 111, or PHYSICS 201 and 211. Global hydrologic cycle, including rivers and weathering, groundwater, rainwater and the atmosphere, oceans, human impacts. Field research required.

315 (Effective through Summer 2021) Water and the Earth 3 (2-3) Course Prerequisite: CHEM 102 or 106 one of MATH 108, 140, 171, 172, 182, 201, 202, or ENGR 107 one of SOE 101, SOE 102, PHYSICS 101, or PHYSICS 201. Global hydrologic cycle, including rivers and weathering, groundwater, rainwater and the atmosphere, oceans, human impacts. Field research required.

318 Wildlife Genetics 3 Course Prerequisite: BIOLOGY 106 BIOLOGY 107 with a C or better one of MATH 106, 108, 140, 171, or a minimum ALEKS math placement score of 80%. Application of genetic tools for wildlife conservation and management, including forensics, detection of rare species, and population estimation. Cooperative: Open to UI degree-seeking students.

320 Sedimentary Petrology and Sedimentation 3 (2-3) Course Prerequisite: SOE 350. Sedimentary rock composition and origins applying fundamental principles of sedimentology. Field trip required.

322 Geology of the Pacific Northwest 3 Course Prerequisite: SOE 101 or 102. Physical geology of the Pacific Northwest focusing on geological processes important in its evolution. Field trips required.

335 [M] Environmental Policy and Law 3 Course Prerequisite: SOE 110. Global, national, and regional environmental issues and policy.

340 [M] Structural Geology and Plate Tectonics 4 (3-3) Course Prerequisite: One of MATH 106, 108, 140, 171, or a minimum ALEKS math placement score of 80% SOE 210. Basic understanding and techniques of working in deformed rocks in mountain belts. Field trip required.

340 (Effective through Summer 2021) [M] Structural Geology and Plate Tectonics 4 (3-3) Course Prerequisite: One of MATH 106, 108, 140, 171, or a minimum ALEKS math placement score of 80% SOE 210. Basic understanding and techniques of working in deformed rocks in mountain belts. Field trip required.

350 Earth Materials 4 (2-6) Course Prerequisite: CHEM 101 or 105 SOE 101, 102, 210, or 230. Composition, physical properties, structure, crystallography, identification, and origin of minerals. Field trip required.

356 Magmatic Processes 3 (2-3) Course Prerequisite: SOE 350. Study of volcanic activity, generation and evolution of magma, and the formation and growth of Earth's crust. Field trips required.

356 (Effective through Summer 2021) Magmatic Processes 3 (2-3) Course Prerequisite: SOE 350. Study of volcanic activity, generation and evolution of magma, and the formation and growth of Earth's crust. Field trips required. (Formerly GEOLOGY 356).

357 Introduction to Metamorphic Rocks and Minerals and How They Impact Our World 3 (2-3) Fundamental processes in the field of earth sciences application of theoretical concepts from metamorphism to challenges and realities of the modern world, including climate, earthquakes, and industry.

357 (Effective through Summer 2021) Introduction to Metamorphic Rocks and Minerals and How They Impact Our World 3 (2-3) Fundamental processes in the field of earth sciences application of theoretical concepts from metamorphism to challenges and realities of the modern world, including climate, earthquakes, and industry.

390 Living on the Edge: Global Climate Change and Earth History 3 Course Prerequisite: Junior standing. Global earth system: ocean, earth, atmosphere, biosphere, and cryosphere human impact on the climate system climate change data predictions debates.

402 Human Health and the Environment 3 Problem-solving approach to adverse effects on human health caused by contamination of environmental media or anthropogenic changes in ecosystems.

403 Sampling for Terrestrial Ecosystem Management 3 (2-3) Course Prerequisites: SOE 204 STAT 212 or 412. Simple random sampling, stratified sampling, and sampling in proportion to importance foundation presented for selecting a sampling scheme, implementing it in the field, and assessing variance.

404 [CAPS] [M] The Ecosystem 3 Course Prerequisite: SOE 110 BIOLOGY 106 BIOLOGY 372 or concurrent enrollment junior standing. Ecosystem organization and processes theory and applications to contemporary environmental problems.

405 Near Surface Geophysics 4 (3-3) Exploration of near surface geophysics techniques as applicable, but not limited to, groundwater analysis, environmental remediation, archaeology, and natural resources detection.

405 (Effective through Summer 2021) Near Surface Geophysics 4 (3-3) Exploration of near surface geophysics techniques as applicable, but not limited to, groundwater analysis, environmental remediation, archaeology, and natural resources detection.

406 Introduction to Radiological Science 3 Course Prerequisite: One course each in biology, calculus, chemistry, and physics. Fundamentals of atomic physics, interactions of radiation with matter, radiation dosimetry and biology, radioecology, and radiological health protection.

408 [CAPS] [M] Field Geology 3 (0-9) Course Prerequisite: SOE 207 SOE 340 SOE 350 senior standing. Advanced field problems and methods data interpretation and report preparation. Cooperative: Open to UI degree-seeking students.

411 [M] Limnology and Aquatic Ecosystem Management 3 (2-3) Introduction to the science and management of aquatic ecosystems, emphasizing lakes.

412 [M] Global Biogeochemistry 3 Cycles of biogeochemically important elements and anthropogenic changes to those cycles in terrestrial and aquatic environments on a global scale. Field trip required. Credit not granted for both SOE 412 and SOE 512. Offered at 400 and 500 level.

416 Soil Processes in the Earth's Critical Zone 3 Soil geochemistry and processes theory and applications with a focus on reactions at the solid, liquid, and gaseous interface between the lithosphere, atmosphere, hydrosphere, and biosphere. (Crosslisted course offered as SOE 416/516, SOIL SCI 416/516). Credit not granted for both SOE/SOIL SCI 416 and SOE/SOIL SCI 516. Recommended preparation: Basic knowledge of soils (e.g. SOIL SCI 201 or equivalent CHEM 106 PHYSICS 102). Offered at 400 and 500 level.

417 Fisheries Science and Management 3 Course Prerequisite: SOE 411 or BIOLOGY 412 STAT 212 or MATH 171. Background on the development of fisheries science and examination of the natural and social scientific theories and techniques applied to the management of fisheries.

420 Long-term Research in Forest Ecosystems: Old-growth Forests of Yosemite National Park 3 Course Prerequisite: By instructor permission. Field research methods course in forest ecosystems at site in old-growth mixed-conifer forest in Yosemite National Park. Course usually runs in late May.

430 Introduction to Wildland Fire 3 Course Prerequisite: SOE 300 or BIOLOGY 372 SOE 301. Physical nature and behavior of wildland fire the fire environment fire ecology practice of wildland fire management. Field trip required.

431 Wildlife Nutrition 3 (2-3) Course Prerequisite: BIOLOGY 106 with a C or better BIOLOGY 107 with a C or better junior standing. Nutritional requirements and interactions of wildlife populations. Cooperative: Open to UI degree-seeking students.

435 Wildlife Ecology 4 (3-3) Course Prerequisite: BIOLOGY 372 or SOE 300 STAT 212 or 412 junior standing. The ecology of wildlife species and the contributing biological processes. Overnight field trip required.

438 Natural Resource and Public Lands Policy and Law 3 Course Prerequisite: Junior standing. Development, content and implementation of natural resources and environmental policy and law in the U.S. Emphasis on both historical development and current issues in this field. Recommended preparation: SOE 312.

441 Population Ecology and Conservation 4 (3-3) Course Prerequisite: BIOLOGY 372 or SOE 300 with a C or better in either SOE 435 with a C or better STAT 212 with a C or better and concurrent enrollment in STAT 412, or STAT 412 with a C or better. Ecology, conservation, management of vertebrate populations, especially threatened and endangered species designed for wildlife and conservation biology majors.

441 (Effective through Summer 2021) Population Ecology and Conservation 4 (3-3) Course Prerequisite: BIOLOGY 372 or SOE 300 with a C or better in either SOE 435 with a C or better STAT 212 with a C or better and concurrent enrollment in STAT 412, or STAT 412 with a C or better. Ecology, conservation, management of vertebrate populations, especially threatened and endangered species designed for wildlife and conservation biology majors.

444 Environmental Assessment 3 National and state policy frameworks for environmental assessment that support integration of science and the public into agency decision-making process. Credit not granted for both SOE 444 and SOE 544. Offered at 400 and 500 level. Cooperative: Open to UI degree-seeking students.

444 (Effective through Summer 2021) Environmental Assessment 3 National and state policy frameworks for environmental assessment that support integration of science and the public into agency decision-making process. Credit not granted for both SOE 444 and SOE 544. Offered at 400 and 500 level. Cooperative: Open to UI degree-seeking students.

445 Hazardous Waste Management 3 Environmental, technical, and political aspects of hazardous waste management evaluative methods, risk assessment, and current management requirements. Credit not granted for both SOE 445 and SOE 545. Offered at 400 and 500 level. Cooperative: Open to UI degree-seeking students.

446 [M] Wildlife Habitat Ecology 3 (2-3) Course Prerequisite: SOIL SCI 368 or concurrent enrollment STAT 212 or 412 senior standing. The ecology of how wildlife use, respond to, and affect resources in their environment.

446 (Effective through Summer 2021) [M] Wildlife Habitat Ecology 3 (2-3) Course Prerequisite: SOIL SCI 368 or concurrent enrollment. The ecology of how wildlife use, respond to, and affect resources in their environment.

450 [M] Conservation Biology 3 Course Prerequisite: Junior standing. Patterns of biological diversity, factors producing changes in diversity, values of diversity, management principles applied to small populations, protected areas, landscape linkages, biotic integrity, restoration, legal issues and funding sources.

454 [CAPS] [M] Restoration Ecology 3 (2-3) Course Prerequisite: Senior standing. Ecological principles used to restore biological communities ecological processes and species on degraded landscapes.

460 Biotechnology and the Environment 3 Course Prerequisite: BIOLOGY 106, 107, or 120 3 credit hours CHEM. Benefits, regulations, and human and environmental impacts of biotechnology used for crop protection, agricultural and energy production, and environmental remediation and management. (Crosslisted course offered as ENTOM 460, SOE 460).

461 Watershed Management 3 Principles and practices of management of forest and rangelands for protection, maintenance, and improvement of water resource values. Field trip required. Recommended preparation: SOE 204 or sufficient background in spreadsheets.

463 Water in the Environment 3 Course Prerequisite: MATH 140 or 171, or 4 credits PHYSICS 101 or 201, or PHYSICS 101 and 111, or PHYSICS 201 and 211, or PHYSICS 205. Water flows in the natural environment, including cloud formation, rainfall, evaporation, infiltration, groundwater, river flows, lakes, estuaries, mixing, and erosion.

463 (Effective through Summer 2021) Water in the Environment 3 Course Prerequisite: One semester of MATH 140, 171, PHYSICS 101, 201, or 205. Water flows in the natural environment, including cloud formation, rainfall, evaporation, infiltration, groundwater, river flows, lakes, estuaries, mixing, and erosion.

464 [M] Landscape Ecology 3 (2-3) Course Prerequisite: Junior standing. Linkages between spatial patterns and processes in a variety of landscapes and the qualitative tools used in the investigation of these linkages.

465 Aquatic Microbial Ecology 2 Course Prerequisite: BIOLOGY 372. Biological, ecological and environmental impact of microbes in aquatic systems.

470 Introduction to Economic Geology 3 (2-3) Course Prerequisite: SOE 340 SOE 350. Genesis, evolution and tectonic setting of ore deposits combining theory, description, and detailed hand specimen analysis. Field trip to major mining districts. Cooperative: Open to UI degree-seeking students.

471 [CAPS] International Wildlife Conservation 3 Course Prerequisite: Junior standing. A broad survey of international wildlife conservation that touches on biological, social, and political aspects of wildlife management focus on understanding the unique challenges that are encountered in the international arena.

474 [CAPS] [M] Physics and Chemistry of the Earth 4 (3-3) Course Prerequisite: CHEM 101 or 105 CHEM 102 or 106 4 credits of PHYSICS 101 or 201, or PHYSICS 101 and 111, or PHYSICS 201 and 211 SOE 101, 102, or 210 junior standing. Earth's operations as described by sub-disciplines of geology, chemistry, physics, and mathematics earth's composition as related to solar system formation.

474 (Effective through Summer 2021) [CAPS] [M] Physics and Chemistry of the Earth 4 (3-3) Course Prerequisite: CHEM 101 or 105 CHEM 102 or 106 MATH 171 PHYSICS 101 or 201 SOE 101, 102, or 210 junior standing. Earth's operations as described by sub-disciplines of geology, chemistry, physics, and mathematics earth's composition as related to solar system formation.

475 Groundwater 3 (2-3) Course Prerequisite: CE 317 or SOE 315 MATH 140 or concurrent enrollment, or MATH 172 or 182 or concurrent enrollment. Introduction to groundwater occurrence, movement, quality, and resource management, emphasizing physical and biogeochemical principles. Field trip required. (Crosslisted course offered as SOE 475, CE 475). Cooperative: Open to UI degree-seeking students.

476 Biology and Ecology of Pacific Salmon 3 Course Prerequisite: BIOLOGY 106 or 107 CHEM 101 or 105. The life histories, habitat requirements, and current issues facing Pacific salmon. Credit not granted for both SOE 476 and SOE 576. Offered at 400 and 500 level.

477 [CAPS] Environmental Dispute Resolution and Conflict Management 3 Course Prerequisite: Junior standing. Exploration of the consequences of complex social, economic, and environmental dynamics that lead to disputes and conflicts over environmental and natural resources develop toolbox of skills and approaches that may be used to facilitate collaborative solutions and resolution of disputes.

480 How to Build a Habitable Planet 3 An introduction to the origin and evolution of Earth including the effects of water, CO2, and humans on the planet exploration of radioactive decay, geochronology, radiogenic and stable isotope geochemistry, and chemical proxies in dynamic systems.

480 (Effective through Summer 2021) How to Build a Habitable Planet 3 An introduction to the origin and evolution of Earth including the effects of water, CO2, and humans on the planet exploration of radioactive decay, geochronology, radiogenic and stable isotope geochemistry, and chemical proxies in dynamic systems.

483 Sustainability: Applied Improvement or Promotion Projects 3 Course Prerequisite: Minimum 3 credits of [PSCI] or [BSCI] senior standing. An applied multidisciplinary introduction to sustainability classroom learning followed with an applied sustainability improvement or promotion project for Washington State University.

484 Forest Management and Planning 3 Knowledge, skills, and experience in drafting a management plan and managing forested properties for a variety of values, ranging from generation of diverse forest products to maintenance of important environmental values associated with forest lands.

485 Disturbance Ecology 3 (2-3) Course Prerequisite: SOE 204 SOE 301 SOE 302 or concurrent enrollment. Fire, disease, and other disturbances are primary drivers of structure and composition in terrestrial ecosystems study of management of insect outbreaks and fungal organisms in combination with fire and other disturbances.

486 Applied Remote Sensing: From Drones to Satellites 3 Course Prerequisite: SOIL SCI 368 or concurrent enrollment, or SOIL SCI 374 or concurrent enrollment. Remote sensing to measure changes in forests, plants, wildlife, wildfire, crops, and geologic features analyzing and applying data from satellites, drones, airplanes, and lidar to measures on the ground.

486 (Effective through Summer 2021) Applied Remote Sensing: From Drones to Satellites 3 Remote sensing to measure changes in forests, plants, wildlife, wildfire, crops, and geologic features analyzing and applying data from satellites, drones, airplanes, and lidar to measures on the ground.

491 Senior Seminar 1 Course Prerequisite: Senior standing. Recommended preparation: Admission to a major in science, mathematics, or engineering.

492 Special Topics V 1-3 May be repeated for credit cumulative maximum 12 hours. Specialized topics within the discipline content will vary each term. Open to all SOE majors. Cooperative: Open to UI degree-seeking students.

495 Undergraduate Internship V 1-12 May be repeated for credit cumulative maximum 12 hours. Course Prerequisite: By interview only. Practical experience in appropriate agencies for career students in earth science, environment and ecosystem science, forestry, and wildlife. S, F grading.

498 Seminar 1 May be repeated for credit cumulative maximum 3 hours. Research papers presented by students, faculty, and visiting scientists on geological research. Credit not granted for both SOE 498 and SOE 598. Offered at 400 and 500 level. S, F grading.

499 Special Problems V 1-4 May be repeated for credit. Independent study conducted under the jurisdiction of an approving faculty member may include independent research studies in technical or specialized problems selection and analysis of specified readings development of a creative project or field experiences. S, F grading.

501 Graduate Skills Seminar 1 Seminar designed to introduce first year graduate students to the science graduate program roles and responsibilities of graduate students, teaching assistants and researchers. S, F grading.

505 Geodynamics 4 (3-3) Overview of topics in geodynamics including conductive and convective heat transfer, mantle convection, plate flexure, faulting, and plate tectonics. Recommended preparation: Calculus and introductory physics.

510 Species Distribution Modeling 3 Theory and application of species distribution models, including niche, occupancy, and spatial capture-recapture models manipulation of spatial data and software packages (ArcGIS, R, MaxEnt, PRESENCE). Cooperative: Open to UI degree-seeking students.

512 [M] Global Biogeochemistry 3 Cycles of biogeochemically important elements and anthropogenic changes to those cycles in terrestrial and aquatic environments on a global scale. Field trip required. Credit not granted for both SOE 412 and SOE 512. Offered at 400 and 500 level.

516 Soil Processes in the Earth's Critical Zone 3 Soil geochemistry and processes theory and applications with a focus on reactions at the solid, liquid, and gaseous interface between the lithosphere, atmosphere, hydrosphere, and biosphere. (Crosslisted course offered as SOE 416/516, SOIL SCI 416/516). Credit not granted for both SOE/SOIL SCI 416 and SOE/SOIL SCI 516. Recommended preparation: Basic knowledge of soils (e.g. SOIL SCI 201 or equivalent CHEM 106 PHYSICS 102). Offered at 400 and 500 level.

520 Radiation Instrumentation 3 (2-3) Methods for analysis of radiation and radiative materials, including use of radiation monitoring equipment and analysis of instrument data.

521 Uses and Regulation of Radiation 3 Uses and regulation of radiation and radioactive materials in medicine, industry, power production, and scientific research.

524 Advanced Topics in Sedimentology 3 (2-3) May be repeated for credit cumulative maximum 6 hours. Modern aspects of sedimentary rocks. Field trip required. Cooperative: Open to UI degree-seeking students.

526 Ecology of the Columbia River 3 Interdisciplinary approach to the interconnections between the physical, geological, chemical, biological, and social dimensions of this large, iconic aquatic ecosystem. Recommended preparation: BIOLOGY 372.

531 Fundamentals of Environmental Toxicology 3 Fundamentals of toxicology environmental fate and biological effects of chemical pollutants in air, water, and food.

532 Applied Environmental Toxicology 3 Overview of and current issues in the field of environmental toxicology.

532 (Effective through Summer 2021) Applied Environmental Toxicology 3 Course Prerequisite: SOE 531 or PHARMSCI 505. Overview of the field of environmental toxicology interactions of zenobiotics with natural systems.

535 Integrated Water Resources Science and Management 3 Introduction to the physical, social, and cultural drivers that shape how water is managed within the larger environmental and human landscape.

536 Climate Change Impacts on Physical, Natural, and Human Systems 3 Methods for studying human-caused climate variability and change discussion of impacts on the physical environment and natural and human systems.

536 (Effective through Summer 2021) Climate Change Impacts on Physical, Natural, and Human Systems 3 Methods for studying human-caused climate variability and change discussion of impacts on the physical environment and natural and human systems.

540 Agroecology 3 Social and ecological aspects of agriculture and human food systems.

540 (Effective through Summer 2021) Agroecology 3 Social and ecological aspects of agriculture and human food systems.

541 Orogenic Systems 3 (2-3) Detailed analysis of the construction of mountain belts. Field trip required. Recommended preparation: B.S. in Geology or related field. Cooperative: Open to UI degree-seeking students.

542 Extensional Tectonics 3 Case study of Western US Basin and Range Province to explore processes and dynamics of extensional tectonics. Field trip required. Recommended preparation: B.S. in Geology or a related field. Cooperative: Open to UI degree-seeking students.

544 Environmental Assessment 3 National and state policy frameworks for environmental assessment that support integration of science and the public into agency decision-making process. Credit not granted for both SOE 444 and SOE 544. Offered at 400 and 500 level. Cooperative: Open to UI degree-seeking students.

544 (Effective through Summer 2021) Environmental Assessment 3 National and state policy frameworks for environmental assessment that support integration of science and the public into agency decision-making process. Credit not granted for both SOE 444 and SOE 544. Offered at 400 and 500 level. Cooperative: Open to UI degree-seeking students.

545 Hazardous Waste Management 3 Environmental, technical, and political aspects of hazardous waste management evaluative methods, risk assessment, and current management requirements. Credit not granted for both SOE 445 and SOE 545. Offered at 400 and 500 level. Cooperative: Open to UI degree-seeking students.

548 Applied Spatial Ecology 3 Foundational research principles in spatial ecology applied to new data production of methods and results sections suitable for publication, using R and GIS programming. Recommended preparation: Introductory-level experience with R and ArcGIS.

555 System Dynamics Models of Environmental Systems 3 Analysis of environmental system dynamics development and uses of simulation models using the Stella software on Macintosh. Cooperative: Open to UI degree-seeking students.

556 Foraging Ecology of Herbivores 2 Synthesis of foraging behavior concepts including nutritive quality of forages, digestive and metabolic constraints, and diet and habitat selection. Cooperative: Open to UI degree-seeking students.

560 Advanced Igneous Petrology 3 (2-3) Origin, evolution, and tectonic significance of igneous rocks. Field trip required. Cooperative: Open to UI degree-seeking students.

562 Watershed Biogeochemistry 3 Sources, transformations, fates and impacts of biogeochemically important compounds as they move downstream through watersheds to the coastal zone.

576 Biology and Ecology of Pacific Salmon 3 The life histories, habitat requirements, and current issues facing Pacific salmon. Credit not granted for both SOE 476 and SOE 576. Offered at 400 and 500 level.

577 Advanced Environmental Hydrology 2 Water (ground, soil, surface, plant, atmosphere) dynamics and support of ecosystem functions and organization in natural, disturbed, and human/impacted systems. Recommended preparation: college-level physics, multivariate calculus, and introduction to hydrology.

577 (Effective through Fall 2021) Advanced Environmental Hydrology 3 Principles, dynamics, interactions, and calculations of water flow in the environment (rivers, lakes, groundwater, soil and plant water, atmospheric boundary layer). Recommended preparation: college-level physics, multivariate calculus, and introduction to hydrology.

583 Radiogenic Isotopes and Geochronology 3 Radiogenic isotopes and their uses as chronometers (radiometric dating) and as tracers of earth evolution and differentiation. Cooperative: Open to UI degree-seeking students.

584 Stable Isotope Geochemistry 3 Principles and applications of isotope geochemistry in the geological sciences. Cooperative: Open to UI degree-seeking students.

592 Advanced Topics in Environmental and Natural Resource Sciences V 1-4 May be repeated for credit cumulative maximum 6 hours. Course Prerequisite: By instructor permission.

593 Graduate Seminar in Earth and Environmental Sciences 1 May be repeated for credit cumulative maximum 8 hours.

594 Environmental and Natural Resources Issues and Ethics 3 Ethical systems applied to natural resources issues of professionalism and ethics in natural resource management. Cooperative: Open to UI degree-seeking students.

597 Advanced Topics in Geology V 1-4 May be repeated for credit cumulative maximum 6 hours. Topics of current interest in geology.

598 Seminar 1 May be repeated for credit cumulative maximum 3 hours. Research papers presented by students, faculty, and visiting scientists on geological research. Credit not granted for both SOE 498 and SOE 598. Offered at 400 and 500 level. S, F grading.

600 Special Projects or Independent Study V 1-18 May be repeated for credit. Independent study, special projects, and/or internships. Students must have graduate degree-seeking status and should check with their major advisor before enrolling in 600 credit, which cannot be used toward the core graded credits required for a graduate degree. S, F grading.

700 Master's Research, Thesis, and/or Examination V 1-18 May be repeated for credit. Independent research and advanced study for students working on their master's research, thesis and/or final examination. Students must have graduate degree-seeking status and should check with their major advisor/committee chair before enrolling for 700 credit. S, U grading.

702 Master's Special Problems, Directed Study, and/or Examination V 1-18 May be repeated for credit. Independent research in special problems, directed study, and/or examination credit for students in a non-thesis master's degree program. Students must have graduate degree-seeking status and should check with their major advisor/committee chair before enrolling for 702 credit. S, U grading.

800 Doctoral Research, Dissertation, and/or Examination V 1-18 May be repeated for credit. Course Prerequisite: Admitted to a School of the Environment PhD program. Independent research and advanced study for students working on their doctoral research, dissertation and/or final examination. Students must have graduate degree-seeking status and should check with their major advisor/committee chair before enrolling for 800 credit. S, U grading.


Thesis Deadlines and Approval Process

Thesis deadlines are posted on The Graduate College website under "Current Students." The completed thesis must be submitted to the chair of the thesis committee on or before the deadlines listed on The Graduate College website.

The following must be submitted to The Graduate College by the thesis deadline listed on The Graduate College website:

  1. The Thesis Submission Approval Form bearing original (wet) and/or electronic signatures of the student and all committee members.
  2. One (1) PDF of the thesis in final form, approved by all committee members, uploaded in the online Vireo submission system.

After the dean of The Graduate College approves the thesis, Alkek Library will harvest the document from the Vireo submission system for publishing in the Digital Collections database (according to the student's embargo selection). NOTE: MFA Creative Writing theses will have a permanent embargo and will never be published to Digital Collections.

While original (wet) signatures are preferred, there may be situations as determined by the chair of the committee in which obtaining original signatures is inefficient or has the potential to delay the student's progress. In those situations, the following methods of signing are acceptable:

  • signing and faxing the form
  • signing, scanning, and emailing the form
  • notifying the department in an email from their university's or institution's email account that the committee chair can sign the form on their behalf
  • electronically signing the form using the university's licensed signature platform.

If this process results in more than one document with signatures, all documents need to be submitted to The Graduate College together.

No copies are required to be submitted to Alkek Library. However, the library will bind copies submitted that the student wants bound for personal use. Personal copies are not required to be printed on archival quality paper. The student will take the personal copies to Alkek Library and pay the binding fee for personal copies.

Master's level courses in Biology: BIO


Advantages of Simple Random Sampling

One of the best things about simple random sampling is the ease of assembling the sample. It is also considered as a fair way of selecting a sample from a given population since every member is given equal opportunities of being selected.

Another key feature of simple random sampling is its representativeness of the population. Theoretically, the only thing that can compromise its representativeness is luck. If the sample is not representative of the population, the random variation is called sampling error.

An unbiased random selection and a representative sample is important in drawing conclusions from the results of a study. Remember that one of the goals of research is to be able to make conclusions pertaining to the population from the results obtained from a sample. Due to the representativeness of a sample obtained by simple random sampling, it is reasonable to make generalizations from the results of the sample back to the population.


Types of Sampling Methods and Techniques in Research

The main goal of any marketing or statistical research is to provide quality results that are a reliable basis for decision-making. That is why the different types of sampling methods and techniques have a crucial role in research methodology and statistics.


Your sample is one of the key factors that determine if your findings are accurate. Making the research with the wrong sample designs, you will almost surely get various misleading results.

On this page you will learn:

  • What is sampling?
  • The various types of sampling methods: briefly explained.
    Probability and non-probability sampling.
  • Infographic in PDF.

What is sampling?

Dy definition, sampling is a statistical process whereby researchers choose the type of the sample. The crucial point here is to choose a good sample.

What is a population?

In sampling meaning, a population is a set of units that we are interested in studying. These units should have at least one common characteristic. The units could be people, cases (organizations, institutions), and pieces of data (for example – customer transactions).

What is a sample?

A sample is a part of the population that is subject to research and used to represent the entire population as a whole. What is crucial here is to study a sample that provides a true picture of the whole group. Often, it’s not possible to contact every member of the population. So, only a sample is studied when conducting statistical or marketing research.

There are two basic types of sampling methods:

Probability Sampling

What is probability sampling?

In simple words, probability sampling (also known as random sampling or chance sampling) utilizes random sampling techniques and principles to create a sample. This type of sampling method gives all the members of a population equal chances of being selected.

For example, if we have a population of 100 people, each one of the persons has a chance of 1 out of 100 of being chosen for the sample.

Advantages of probability sampling :

  • A comparatively easier method of sampling
  • Lesser degree of judgment
  • High level of reliability of research findings
  • High accuracy of sampling error estimation
  • Can be done even by non-technical individuals
  • The absence of both systematic and sampling bias.

Disadvantages:

  • Monotonous work
  • Chances of selecting specific class of samples only
  • Higher complexity
  • Can be more expensive and time-consuming.

Types of Probability Sampling Methods

Simple Random Sampling

This is the purest and the clearest probability sampling design and strategy. It is also the most popular way of a selecting a sample because it creates samples that are very highly representative of the population.

Simple random is a fully random technique of selecting subjects. All you need to do as a researcher is ensure that all the individuals of the population are on the list and after that randomly select the needed number of subjects.

This process provides very reasonable judgment as you exclude the units coming consecutively. Simple random sampling avoids the issue of consecutive data to occur simultaneously.

Stratified Random Sampling

A stratified random sample is a population sample that involves the division of a population into smaller groups, called ‘strata’. Then the researcher randomly selects the final items proportionally from the different strata.

It means the stratified sampling method is very appropriate when the population is heterogeneous. Stratified sampling is a valuable type of sampling methods because it captures key population characteristics in the sample.

In addition, stratified sampling design leads to increased statistical efficiency. Each stratа (group) is highly homogeneous, but all the strata-s are heterogeneous (different) which reduces the internal dispersion. Thus, with the same size of the sample, greater accuracy can be obtained.

Systematic Sampling

This method is appropriate if we have a complete list of sampling subjects arranged in some systematic order such as geographical and alphabetical order.

The process of systematic sampling design generally includes first selecting a starting point in the population and then performing subsequent observations by using a constant interval between samples taken.

This interval, known as the sampling interval, is calculated by dividing the entire population size by the desired sample size.

For example, if you as a researcher want to create a systematic sample of 1000 workers at a corporation with a population of 10000, you would choose every 10th individual from the list of all workers.

Cluster Random Sampling

This is one of the popular types of sampling methods that randomly select members from a list which is too large.


A typical example is when a researcher wants to choose 1000 individuals from the entire population of the U.S. It is impossible to get a complete list of every individual. So, the researcher randomly selects areas (such as cities) and randomly selects from within those boundaries.

Cluster sampling design is used when natural groups occur in a population. The entire population is subdivided into clusters (groups) and random samples are then gathered from each group.

Cluster sampling is a very typical method for market research. It’s used when you can’t get information about the whole population, but you can get information about the clusters.

The cluster sampling requires heterogeneity in the clusters and homogeneity between them. Each cluster must be a small representation of the whole population.

Non-probability Sampling

The key difference between non-probability and probability sampling is that the first one does not include random selection. So, let’s see the definition.

What is non-probability sampling?

Non-probability sampling is a group of sampling techniques where the samples are collected in a way that does not give all the units in the population equal chances of being selected. Probability sampling does not involve random selection at all.

For example, one member of a population could have a 10% chance of being picked. Another member could have a 50% chance of being picked.

Most commonly, the units in a non-probability sample are selected on the basis of their accessibility. They can be also selected by the purposive personal judgment of you as a researcher.

Advantages of non-probability sampling:

  • When a respondent refuses to participate, he may be replaced by another individual who wants to give information.
  • Less expensive
  • Very cost and time effective.
  • Easy to use types of sampling methods.

Disadvantages of non-probability sampling:

  • The researcher interviews individuals who are easily accessible and available. It means the possibility of gathering valuable data is reduced.
  • Impossible to estimate how well the researcher representing the population.
  • Excessive dependence on judgment.
  • The researchers can’t calculate margins of error.
  • Bias arises when selecting sample units.
  • The correctness of data is less certain.
  • It focuses on simplicity instead of effectiveness.

Types of Non-Probability Sampling Methods

There are many types of non-probability sampling techniques and designs, but here we will list some of the most popular.

Convenience Sampling

As the name suggests, this method involves collecting units that are the easiest to access: your local school, the mall, your nearest church and etc. It forms an accidental sample. It is generally known as an unsystematic and careless sampling method.

Respondents are those “who are very easily available for interview”. For example, people intercepted on the street, Facebook fans of a brand and etc.

This technique is known as one of the easiest, cheapest, and least time-consuming types of sampling methods.

Quota Sampling

Quota sampling methodology aims to create a sample where the groups (e.g. males vs. females workers) are proportional to the population.

The population is divided into groups (also called strata) and the samples are gathered from each group to meet a quota.

For example, if your population has 40% female and 60% males, your sample should consist those percentages.

Quota sampling is typically done to ensure the presence of a specific segment of the population.

Judgment Sampling

Judgmental sampling is a sampling methodology where the researcher selects the units of the sample based on their knowledge. This type of sampling methods is also famous as purposive sampling or authoritative sampling.

In this method, units are selected for the sample on the basis of a professional judgment that the units have the required characteristics to be representatives of the population.

According to https://explorable.com/ “The process involves nothing but purposely handpicking individuals from the population based on the authority’s or the researcher’s knowledge and judgment.”

Judgmental sampling design is used mainly when a restricted number of people possess the characteristics of interest. It is a common method of gathering information from a very specific group of individuals.

Snowball Sampling

Snowball sampling isn’t one of the common types of sampling methods but still valuable in certain cases.

It is a methodology where researcher recruits other individuals for the study. This method is used only when the population is very hard-to-reach.

For example, these include populations such as working prostitutes, current heroin users, people with drug addicts, and etc. The key downside of a snowball sample is that it is not very representative of the population.

Sampling can be a confusing activity for marketing managers carrying out research projects.


By knowing and understanding some basic information about the different types of sampling methods and designs, you can be aware of their advantages and disadvantages.

The two main sampling methods (probability sampling and non-probability sampling) has their specific place in the research industry.

In the real research world, the official marketing and statistical agencies prefer probability-based samples. While it would always be good to perform a probability-based sampling, sometimes other factors have to be considered such as cost, time, and availability.


Logistics

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This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. Under this license, authorized individuals may copy, distribute, display and perform the work and make derivative works and remixes based on this text only if they give the original author credit (attribution). You are also free to distribute derivative works only under a license identical (“not more restrictive”) to the license that governs this original work.

Dr. Rodney Dyer is an Associate Professor in the Department of Biology and the Assistant Director for the Center for Environmental Studies at Virginia Commonwealth University in Richmond, Virginia, USA. His research focuses on genetic connectivity and structure and how the environment influences both. More information on his research can be found at http://dyerlab.bio.vcu.edu.


PERSPECTIVES ON DIVERSITY, STRUCTURE, AND STABILITY

9.2.3 Some Current and Future Considerations: Food Webs Across Space and Time

Although space has played a large role in population ecology and direct interactions ( McCauley, Wilson, & deRoos 1996 ), the consideration of the role of space on food web dynamics is relatively recent ( Holt 1996 Polis, Anderson, & Holt 1997 Nachman 2001 Callaway & Hastings 2002 McCann et al., in press Teng & McCann 2004 ). In a series of articles, Holt (1996, 2002) and others ( Loreau, Mouquet, & Holt 2003 Holt & Hoopes, in press) have begun to tie metapopulation theory to community and ecosystem perspectives (dubbed metacommunity and metaecosystem, respectively). They have argued cogently that this larger perspective has the potential to unite population, community, and ecosystem perspectives. More specifically, they have argued that expanding the spatial scale of food webs may allow ecologists to more completely understand such long-standing issues as food chain length, trophic control (see also Polis, Anderson, & Holt 1997 ), island biogeography, and food web stability or instability.

Along a similar research theme, some ecologists have begun to consider empirical arguments to frame a more general spatial theory of food webs (McCann, Rasmussen, & Umbanhowar, in review). Polis and Strong (1996) emphasized that different habitats contained different primary producers and that these tended to be coupled by higher-ordered generalist consumers. This result is consistent with two empirical generalizations: (1) that generalist foraging tends to increase with higher-order consumers ( Polis & Strong 1996 Cohen, Jonsson & Carpenter 2003 ) and (2) that higher-order organisms tend to be larger and more mobile than their prey ( Peters 1983 Brown, Stevens, & Kaufman 1996 McCann et al, in press). These relationships are schematically summarized in Figure 9.3 and together create a simple framework for a general spatial theory. Some researchers (McCann et al., in press) have begun to consider the implication of such spatial coupling on the dynamics and stability of coupled food webs. The results suggest that in spatially extended systems with differentially responding resources or prey, behaviour (i.e., movement) by the larger, more mobile organism can act as a potent stabilizing force, especially when considered in a non-equilibrium context.

FIGURE 9.3 . A schematic representation of food webs in space. Higher-order organisms are increasingly more generalized in their foraging and increasingly more mobile. Thus, higher-order organisms couple lower-level habitat compartments.

The result is easily presented and consistent with earlier theory emerging from spatial population ecology (e.g., see McCauley, Wilson, & deRoos 1996 and Fryxell & Lundberg 1997 ). Effectively, larger organisms can respond to variation in space by moving from areas where prey or resource densities are low and towards areas where prey or resource densities are high. The outcome is the release of predatory pressure on prey when prey species are at low densities and increasing predatory pressure when prey species attain high densities—precisely the arrangement needed to reduce extreme variation in density. From the consumer perspective, its rapid behavioural response allows it to track variable resource or prey densities at a larger spatial scale. Clearly, the result relies on the underlying idea that resources in different habitats are responding differentially through time. It turns out that this variation can be abiotically driven or driven by the top-down predatory pressure of generalist consumers if the consumer tends to prefer one organism significantly more than other organisms (this is a manifestation of the weak interaction effect) ( McCann, Hastings, & Huxel 1998 ). So again, like the averaging effect described for a single trophic level ( Tilman, Lehman, & Bristow 1998 ), the notion of differential responses within a non-equilibrium perspective suggest that food web stability may unfold from variability in space and time.

Pimm and Lawton (1980) found little evidence for compartments in food webs except at huge spatial scales or if they considered the coupling of detrital webs to grazing webs. Recent analysis of food webs, using interaction strength or energy flow, found that compartments might be more ubiquitous than early investigations suggested ( Krause et al. 2003 ). It is interesting to reconsider how the coupling of food webs within a spatial perspective will influence the food web compartments. In Figure 9.4A , a food web in which weak and strong interactions are essentially uniformly distributed throughout the food web is depicted. Such a configuration does not drive compartmented food web structure, and in light of the result from Krause and her colleagues’ (2003) , may not characterize natural systems. Figure 9.4B , on the other hand, shows a distribution of interaction strengths that generates strong compartmentalization. Another interesting potential distribution of interaction strengths that generates compartments of a slightly different kind is illustrated in Figure 9.4C . Here, one will find not only a compartmentalized web but also some compartments that may tend to contain stronger interactions than other compartments (i.e., there is the potential not only for weak interactions but also for weak compartments).

FIGURE 9.4 . Three examples of the distribution of weak interactions in a food web. (A) Uniformly distributed weak interactions will not tend to produce compartments even if weak interactions are ignored. (B) Weak interactions are distributed such that food webs have compartments, although weak and strong interactions still exist within individual compartments. (C) Weak interactions are distributed such that food webs have compartments, although weak and strong interactions are positioned such that there also exists the tendency for weak and strong compartment flows.

Soil ecologists have argued for such structure for some time in their underground food webs ( Moore & Hunt 1988 ). They have suggested that bacterial energy channels tend to break down more labile detritus and turn over much more rapidly than fungal energy channels that tend to arise out of more recalcitrant detrital sources. Similarly, an argument can be made for littoral or benthic pathways in lakes versus pelagic pathways in lakes. Benthic invertebrates tend to turn over on a much longer timescale then the rapid turnover of zooplankton on phytoplankton. Finally, it has been suggested for some time that detrital webs are slower and more donor-controlled than grazing webs. Teng and McCann (2004) recently reconsidered the stabilizing role of compartments and found that compartments can be potent stabilizing forces. Again, particularly if compartments (like species) tend to respond differentially in time, behavioural responses by higher-order consumers can then average across these variable out-of-phase subsystems. Hence, strong and weak compartments could be an important form of food web structure that contributes to the persistence of ecological systems.


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