lab quiz 1 Flashcards
phytophages
leaf eating insects
frugivores
fruit eating insects
Monarch butterfly
feeds on milkweed. Produces milky sap which acts as skin irritant. Monarch butterflies consume this plant and then are poisonous to birds that eat them
Simple random sampling
pooling all groups together and choosing number… for leaf experiment could have ended up with 15 leaves from tolmie and 5 leaves from uvic
Stratified random sampling
dividing into groups first… then randomly selecting from those groups
3 ecological issues concerning the effects of herbivory
1) Herbivores at controlled levels vs outbreak levels
2) effects of herbivores on primary productivity
3) what factors control herbivores? ex. plant chemistry, food quality, defense chemicals etc.
pseudoreplication
- treating samples that are not independent as independent samples… decreases validity
- measuring leaves on trees, want to have an estimate population at each position… 2 leaves from the same trees and averaging isn’t good
What does the confidence interval mean if it does not include 0
means there is a difference
What does it mean if the p-value is less than the alpha value
-there is evidence to reject Ho and lend support for Ha
what does an alpha value of 0.05 mean
means that the p-value would have a 5% chance of error
Pros of stratified random sampling?
-controls for other variables
Cons of stratified random sampling
- when researchers can’t classify every member of a population into a subgroup
- overlapping: when subjects fall into multiple subgroups
Pros simple random samling
-easy and accurate
cons simple random samplihgn
- pools all the numbers… samples that are way out of the normal range will deviate the results a lot…
- doesn’t control for variables so much
what are gary oaks named after?
Nicholas Gary
Where trees are Gary oaks found around
1) arbutus
2) Douglas Fir
why is variation in a trait important
for its ability to evolve thru natural selection
how is the mean value useful
1) sometimes the best representation of a population
2) the mean can be used for comparing populations or samples
What did Darwin say the reason for differences between species was
said that the differences we observe between species may arise from variation in properties within a species
A bar graph of the numbers of whelks in each size class is called a ________
size frequency distribution
what does a larger aperture size mean in whelks? and why?
larger foot… this is an adaptation to wave action
What does a bigger foot mean in whelks
greater power of adhesion and therefore a whelk from a more exposed habitat should have a larger foot
as predation pressure increases… what happens to the whelks
whelks will have thicker shell
Different between transect and quadrat sampling
transect- any line marked at regular intervals
quadrat - framed area
how to calculate shell aperture index
Ia = [ (∏ (L+w/4)^2)/h ]
main factors that influence whelk morphology: sheltered vs. exposed habitat
Sheltered: predators
Exposed: Wave action
Positively skewed data
Shampoo example: several caps were tightened much harder than they should be
What does it mean when error bars overlap?
While the means APPEAR to be different, the difference is probably not significant
Interval Bar
a vertical bar with horizontal endpoints of the 95% CI for the mean
Standard error bar
a vertical line with horizontal endpoints at one or multiple standard errors
Main difference between bar charts and histograms
the x-axis of bar charge represents a “categorial” variable. The x-axis on a histogram represents a continuous, “quantitative” variable
Skewness and symmetry of…
you can only talk about skewness or symmetry of histograms… that is the tendency of observations to fall more on the low or the high end of the x-axis.
when is a scatterplot used
when you have bivariate data (2 variables)
What does linear regression attempt to do
attempts to model the relationship between the data
Difference between line and point transects
line transects- recording of data is continuous
point transects- recording of data occurs at regular intervals and for a given duration at each point
why are transects good
they are highly adaptable and efficient
Random transect approach
starting points and directions at random
Stratified random approach
starting points and directions at random BUT where each lies within an individual habitat stratum
What are quadrants most appropriately used for
sessile animal or plant populations
What do you have to decide before using quadrants
1) the # of quadrats
2) the size of the quadrants
3) the placement of the quadrats
