Ecology Sampling Methods

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Questions and Answers

Match the following terms with their descriptions:

Observed values = The actual count of each category in the data Expected values = The theoretical count of each category if there's no association Degrees of Freedom = The number of values in the final calculation of chi-squared Chi-squared value = A measure of the difference between observed and expected values

Match the following statistical concepts with their purposes:

Chi-squared test = Testing for association between two categorical variables Degrees of Freedom = Determining the number of values in the final calculation Critical value = Comparing the calculated chi-squared value to determine significance Null hypothesis = The assumption that there's no association between the variables

Match the following steps with their descriptions:

Calculate the Chi2 value = Using the observed and expected values to determine the chi-squared value Compare the calculated value to the critical value = Determining if the result is statistically significant Determine the degrees of freedom = Calculating the number of values in the final calculation Reject or fail to reject the null hypothesis = Deciding whether the association is statistically significant

Match the following values with their descriptions:

3.84 = The critical chi-squared value for 1 degree of freedom at p = 0.05 7.65 = The calculated chi-squared value in the example 0.05 = The probability level for the chi-squared test 1 = The degrees of freedom for the chi-squared test Signup and view all the answers

Match the following conclusions with their descriptions:

Reject the null hypothesis = The association between the variables is statistically significant Fail to reject the null hypothesis = The association between the variables is not statistically significant The distributions are independent = The variables are not associated The distributions are associated = The variables are statistically significantly associated Signup and view all the answers

Match the following terms with their definitions:

Statistical significance = The result is unlikely to occur by chance Association = A relationship between two categorical variables Independence = No relationship between two categorical variables p-value = The probability of obtaining the result by chance Signup and view all the answers

Match the following values with their descriptions:

120 = The total count of Bell heather present 80 = The total count of Bell heather absent 134 = The total count of Ling present 66 = The total count of Ling absent Signup and view all the answers

Match the following steps with their purposes:

Calculate the expected values = Determining the theoretical count of each category Calculate the chi-squared value = Determining the difference between observed and expected values Compare the calculated value to the critical value = Determining statistical significance Interpret the result = Deciding whether the association is statistically significant Signup and view all the answers

Match the following terms with their descriptions:

Critical region = The area of the distribution where the null hypothesis is rejected p-value = The probability of obtaining the result by chance Type I error = Rejecting the null hypothesis when it's true Type II error = Failing to reject the null hypothesis when it's false Signup and view all the answers

Match the following statistical concepts with their descriptions:

Chi-squared distribution = A probability distribution used in the chi-squared test Degrees of freedom = The number of values in the final calculation of chi-squared Significance level = The maximum probability of rejecting the null hypothesis when it's true Confidence interval = A range of values within which the true population parameter is likely to lie Signup and view all the answers

Match the following steps with their descriptions:

Determine the research question = Defining the problem or question to be answered Collect and organize the data = Gathering and preparing the data for analysis Conduct the chi-squared test = Calculating the chi-squared value and determining statistical significance Interpret the results = Deciding whether the association is statistically significant Signup and view all the answers

Study Notes

Sampling Methods for Sessile Organisms

Quadrat sampling: a method to measure an area without bias, suitable for sessile organisms like plants or small, slow-moving animals.
Belt transects: a sampling method that takes samples from an area along a straight line.

Quadrat Sampling

Random quadrat sampling: used to estimate population size, involves randomly placing quadrats within a selected area.
Eliminates bias that may influence measurements.

Motile Organisms

Harder to sample than plants due to their movement.
Methods to collect animals include:
- Pitfall traps
- Pouters (aspirators)
- Mammal traps
- Nets

Capture-Mark-Release-Recapture (CMRR) Method

Used to estimate population size for motile organisms.
Involves capturing, marking, releasing, and recapturing animals to determine the population size.
The Lincoln index is used to calculate the population size (N) of mobile animals.

Predator-Prey Relationships

An example of density-dependent control of animal populations.
When a predator kills its prey, the prey population becomes smaller.
Cyclic oscillations can occur when predator and prey populations are out of sync.

Top-Down and Bottom-Up Control of Populations

Top-down control: occurs when a higher trophic level affects a lower one.
Bottom-up control: occurs when a lower trophic level affects a higher one.

Keystone Species

Exerts top-down influence on its community by reducing the number of species at lower trophic levels.

Allelopathy and Secretion of Antibiotics

Some organisms produce secondary metabolites to deter competitors from their ecological niche.

Testing for Association: Chi-Squared Test

Used to determine if there is an association between two species.
The chi-squared value is calculated and compared to a critical value to determine statistical significance.

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Description

Learn about the two common sampling methods for sessile organisms: Quadrat Sampling and Line or Belt transects. Understand how to estimate population size using these methods.