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Questions and Answers
What is the primary purpose of using quadrats in population sampling?
What is the primary purpose of using quadrats in population sampling?
- To estimate the population size for stationary organisms (correct)
- To count all the individuals in a population
- To track movements of mobile organisms
- To identify the species diversity in a habitat
Which of the following is a limitation of the quadrat sampling method?
Which of the following is a limitation of the quadrat sampling method?
- It requires advanced technology to implement
- It provides an exact count of population size
- It may result in over or underestimation due to clustering (correct)
- It can only be used with mobile organisms
What is the first step in the mark-recapture method of population estimation?
What is the first step in the mark-recapture method of population estimation?
- Mark a proportion of individuals using advanced technology
- Capture a second sample of organisms
- Capture and mark a group of organisms (correct)
- Evaluate the habitat for clumping
In the mark-recapture method, what does the proportion of marked individuals in the second sample represent?
In the mark-recapture method, what does the proportion of marked individuals in the second sample represent?
Using the mark-recapture formula, if 20 individuals are marked (M) and 50 individuals are recaptured (m), what is the population size estimate (N) if the second sample size (n) is 200?
Using the mark-recapture formula, if 20 individuals are marked (M) and 50 individuals are recaptured (m), what is the population size estimate (N) if the second sample size (n) is 200?
In the provided example, if 48 polar bears are marked and 6 out of 30 recaptured are marked, what is the calculated population size?
In the provided example, if 48 polar bears are marked and 6 out of 30 recaptured are marked, what is the calculated population size?
Why might mark-recapture sampling be preferred over quadrat sampling for certain organisms?
Why might mark-recapture sampling be preferred over quadrat sampling for certain organisms?
Which aspect is NOT a factor considered when using quadrat sampling?
Which aspect is NOT a factor considered when using quadrat sampling?
Flashcards
Mark-recapture sampling
Mark-recapture sampling
A technique used to estimate population size by capturing and marking a sample of organisms, then recapturing another sample and using the proportion of marked individuals to estimate the total population.
Quadrat
Quadrat
A square frame of a specific size used to sample organisms in a habitat.
Random sampling
Random sampling
A method of sampling a population where individuals are selected randomly to represent the entire population.
Stratified sampling
Stratified sampling
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Systematic sampling
Systematic sampling
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Sampling bias
Sampling bias
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Proportion of marked individuals
Proportion of marked individuals
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Factors influencing population size estimates
Factors influencing population size estimates
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Study Notes
Measuring Population Characteristics
- Estimating population size is often difficult, so biologists use sampling techniques.
Sampling Techniques
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Quadrat Sampling (for stationary organisms):
- A quadrat (a frame of a specific size) is placed randomly within a habitat.
- The number of individuals within the quadrat is counted.
- This count is used to estimate the total population size.
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Limitations of quadrat sampling:
- Ineffective for clumped populations. If the quadrat falls within a clump, it will overestimate the population; if it falls between clumps, it will underestimate.
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Mark-Recapture Sampling (for mobile organisms):
- A group of organisms is captured, tagged, and released.
- After a period of time, a second sample is taken.
- The proportion of marked organisms in the second sample is used to estimate the total population size.
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Rationale: If the proportion of marked individuals in the second sample reflects the proportion of marked individuals in the whole population, the total population size can be estimated.
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Mark-Recapture Formula: N = (M * n) / m Where:
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N = Estimated population size
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M = Number of individuals marked in the first sample
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n = Total number of individuals in the second sample
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m = Number of marked individuals in the second sample
Example Calculation
- Example using polar bears:
- 48 polar bears marked initially
- 30 polar bears captured in the second sample
- 6 of the bears in the second sample were marked
- Estimated population size: (48 * 30) / 6 = 240
Assumptions of Mark-Recapture Sampling
- All individuals have an equal chance of being captured.
- The ratio of marked to unmarked individuals stays constant during the study period. This means tagging does not affect survival rates.
- Population size remains constant during the study.
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Description
Explore the various methods used by biologists to estimate population sizes, including quadrat and mark-recapture sampling techniques. This quiz covers the rationale behind these methods, their applications, and limitations. Test your understanding of sampling in ecological studies.
