Lab 2: Effect of stress on plant growth and reproduction Flashcards
What is the difference between an observational experiment or a manipulative experiment?
Observational: measure different variables and look for patterns in the data
Manipulative: intentionally manipulate a variable/factor that you hypothesize is driving the observations you made and controlling as many other competing factors as possible
What is range of tolerance and what are the three categories contained within it?
The entire range of conditions in which a plant can survive.
Optimal performance: small subset of conditions that maximize growth and reproduction (optimum)
Growth and no reproduction: sub-optimal conditions, decreased energy therefore not enough for reproduction, only for growth
Survival, no growth/reproduction: edges of range of tolerance, under stress and energy is used to fight these stresses
What is phenotypic plasticity?
The flexibility of phenotype under different environmental conditions
What are the two criteria to determine whether the sample is representative of the entire population?
Unbiased
Adequate size
What are the three different types of sampling methods?
- Randomly: usual method, use random generators, or draw numbers from hat
- Systematic: taking samples that have some sort of regular arrangement, usually simpler to conduct, bias only present if sampling pattern reveals a pattern in the data
- Combination: random and systematic, only select sites that are representative
What sampling method is usually recommended?
Random, many stats tests are built around this assumption
What are three things to consider when deciding on sampling effort?
Sample size: many small/medium samples are better than large and few
Type of area: a homogenous area needs less sampling
Distribution of population within an area: highly clumped populations may require more samples than random or uniform populations
What is a performance curve? What is a cumulative mean?
A curve that plots the cumulative mean value of a trait against number of samples taken.
A cumulative mean is calculated by summing the total number of objects encountered and then dividing it by the total number of samples up to that point. As you get more samples the true population mean is approached and the curve flattens out, and when the change in cumulative mean becomes very small with the addition of a new sample, we can say that the sample mean has approached the true population mean
What are two ways of measuring population density?
Quadrat method: small, sessile, sedentary organisms
Mark/recapture method: large or mobile organisms
What is the quadrat method?
A quadrat is a sampling area of known/defined size. You must count all the individuals in each quadrat, then extrapolate the average density to the whole area
n=average # sampled in the quadrats
a= size of quadrat
N= total population size
A= total area
N must be a whole number, and always round up regardless of decimals
In order for density estimates based on quadrats to be accurate, what must happen?
Number of individuals in each quadrat must be known exactly
Size of quadrats must be known
Quadrats must be representative of the study area as a whole
What is mark/recapture?
Used to quantify the population density of moving organisms.
Capture a small # of individuals
Mark them
Release back in to population and allow them to disperse
Recapture random sample of individuals
Note the number of marked and unmarked individuals in the sample
M=total number marked in the population
N= total population size
m= number marked in sample
n=total number in sample
What are 4 assumptions for mark/recapture model?
Marks must not be lost or overlooked
No change occurs in ratio of marked to unmarked in population (due to birth,death, immigration and emigration)
Marked and unmarked individuals are similar in all aspects
Probability of recapture is equal for marked/unmarked individuals
When do you use a t-test?
Continuous data
Uses means, variance, sample size
With one independent variable, between two groups
Tells you if two means are significantly different from each other
