BIOL1501: Ecology LAB EXAM 1

notes from lab pre-reading

Lab 1 Learning Goals

Discuss what is – and what is not - science

● Consider biases and sources of error involved in data interpretation

● Describe main characteristics and goals of manipulative and natural experiments

● Identify different ecological interactions in the local urban environment

● Initiate the use of the iNaturalist platform as a means to become an amateur naturalist and citizen scientist

Hypothesis Testing

Hypotheses aim to understand the relationships between variables

variables

the factors that can change or be measured in ann experiment.

scientific question

The main source of inquiry in your study that tries to understand the relationship between variables to explain an observed phenomenon

hypothesis

testable explanation of an observed phenomenon

prediction

a specific result you expect to find if your hypothesis is correct

experimental design

for systematically testing the hypothesis is developed (after hypothesis has been developed) → meant to test specific predictions that arise from the hypothesis about how a predictor variable affects the response variable of interest

manipulative experiment

the researcher manipulates the predictor variable and measures how a response variable changes due to these alterations

independent variable

predictor variable

response variable

dependent variable

natural experiment

No interference with the outcome of the study by changing or controlling a variable; examines the natural variation that is present in living systems; predictor variable → explanatory variable

response variable → observational variable

extraneous variables

unwanted factors that create experimental error

random error

inconsitent deviations in data caused by natural variation

systematic error

refers to consistent, directional shifts in data caused by faculty tools (mis-calibrated scale) or researcher bias (sampling only the edges of a forest instead of the interior)

ecological interactions

• mutualism (+/+)

• antagonism (-/+)

• commensalism (0/+)

• competition (-/-)

• amensalism (0/-)

• neutralism (0/0)

plant-pollinator interactions

mutualistic interaction

• animal pollinators: any animal that acts a vector for a flowering plant’s reproduction, whereby pollen is transferred from the anther (male) to stigma (female part of plant)

co-evolution

when two organims evolve in convert with each other

pollinator syndromes

characteristics of a flower (odor, shape, color)

bees

very important ecologically

green roofs

Green roofs are roofs that are completely or partially covered with plants/vegetation. The term “green” refers to the environmental benefits, not to the color of the vegetation growing on the roof. The floor of a green roof is typically comprised of several layers that support proper growth of vegetation and protect the interior of the building from damage by water and plant root growth (Figure 4). One important function of green roofs is that they promote species diversity in urban environments by offering patches of habitat for plants, birds, and invertebrate animals, such as insects

Lab 3 Learning Goals

Describe the important sections of a lab report

● Be familiar with certain terms in descriptive statistics, including: mean, range, central tendency, variability, and standard deviation

● Use inferential statistics (specifically, a t-test) to compare number of bees per flower on different green roof terraces to test the hypothesis that terrace height impacts bee abundance

range

spread of your data calculated as the difference between your highest and lowest value

• ex: consider the following data set about the length of 5 lizards: 6 cm, 4 cm, 9 cm, 8 cm, 11 cm. The range of the data is 4-11cm

central tendency

refers to the degree to which sample observations are clustered somewhere close to the middle of the range of the entire set of observations

• to visualize: plot a histogram with y-axis = freq. of each sample observation and x-axis = range of observation values that are measured

mean

the sum of all observations/the number of observations (x bar)

normal distributions

represented by a curve that is bell-shaped with the peak of the curve centered at the mean (the area under the curve represents the chance of finding observed values within a data set)

standard deviation of mean

steps away from the mean (creates a range)

comparing 2 groups

How can we know if the difference observed between group means is enough to confidently say that the differences observed between the two samples are not due to random chance and that they represent two populations (groups)? We can use a variety of test statistics to quantify the differences and to then decide if we are willing to reject the hypothesis that states that there is no difference between the two groups (with a small risk of this hypothesis actually being correct). To compare two groups that have independent data (data in condition A is not related to data in condition B), we can use a t-test,

t-test

inferential statistical test to determine if the means of two groups is significant enough to reject the null hypothesis (states there is no difference between 2 groups)

• provides t-value scale of 0-1)

  • comparison between T-value and t-value give probability estimates P-value

T-value

standardized value from formula

Lab 4 Learning Goals

To describe the characteristics and benefits of green roofs

- To understand why species diversity is important and how it can change over time

- To distinguish between species richness and species evenness

- To be able to calculate and interpret Simpson’s Reciprocal Index, a measure of species diversity

species diversity

refers to the number of each species and abundance of individuals per species

species richness

total number of species in an ecosystem

species evennnes

examines total number of individuals per species in an ecosystem and how similar they are for each species

simpson’s reciprocal index

1/measurement of species dominance, values ranging from 0 - 1

• sensitive to changes in the abundance of individuals → needs a good sample size

Lab 5 Learning Goals

To describe characteristics and benefits of urban forests

- To identify different leaf types: broad, scale and needle-like and different leaf arrangements: compound and simple

- To use an identification guide to identify NYC street trees by species and health status using physical characteristics

- To describe Santamour’s Formula and understand how it is used to manage urban forests

- To consider how urban forests contribute to environmental justice and discuss the role that societal factors contribute to inequities

benefits of urban forests

• rainwater management

• temperature regulation

• public health benefits

tree-species identification

leaf types: needle-like, scale-like, broadleaf

broadleaf types: single/compount

compound types: palmately/pinnately

• trunks, roots, leaves, and branches all also indicate the health of a tree

diameter

circumference/pi

• can be measured using diameter at breast height

Lab 2 Learning Goals

• Use Google Scholar to search the scientific literature

  ● Practice oral scientific communication by presenting to the class

  ● Collect field data to test a hypothesis about bee abundance on green roof terraces