Principles of Ecology

Principles of Ecology

Section 13.1: Ecologists Study Relationships (Part 2: Research

Methods)

Unit Objectives

• To be able to summarize the levels of organization that ecologists study.

• To be able to describe and apply research methods ecologists use to study the environment.

In what ways, other than as a food source, might prairie dogs support other species?

Answer to Slide 2

• Prairie dog burrows provide shelter for other animals.

• In digging burrows, prairie dogs increase the nitrogen content in the soil and open up more area for oxygen and water absorption, all which encourage plant growth.

A burrowing owl

Sea Otters: Keystone Species in Pacific Estuaries

• http://www.bbc.co.uk/news/science-environment-23814524

Ecological Research Methods

• From Tape measures and observation via the naked eye to GIS (geographic imaging systems) and sophisticated computer software.

• http://ortho.gis.iastate.edu/client.cgi?zoom=1&x0=553190&y0=4702379&layer=ortho_1930&action=layernaip_2011_nc&pwidth=700&pheight=700

Data Collection

• Observations – simply act of watching something over time.– Examples: Sea otters along the California coast to

see how they affect the coastal ecosystems; prairie dogs and their towns to know where to reintroduce black footed ferrets; the predator/prey relationship of wolves and moose on Isle Royale.

How to Observe

• Naked eye or with binoculars (direct survey)/• Indirect methods include tracks, scat, and

radio telemetry (among other things).

How to Observe

• Radio telemetry is useful for animals that have large home ranges; who have young that disperse; or are migratory.

How to Observe

Negatives: any time you intervene with an animal, you are affecting that animals behavior and, possibly, its survival.

The quality of your data and your overall study can be compromised. We call it introducing sources of error and confounding variables.

Other Examples of Tools for Observation

• Detection of, and or use of light outside of the visible spectrum. – Our vision is very limited. We cannot see in the

infrared or UV spectrums (other organisms can)• We need special equipment to record the sonar

of bats and the songs of whales.• Remote sensing – the use of satellites to

monitor from single organisms all the way up to whole ecosystems.

Counting Organisms

• Censuses – can sometimes count every organism but not usually (not feasible).

• Ways to sample populations:– Transects – ex. Count either side of a transit line.

Counting Organisms

– Laying out a grid and then, with a random number generator, randomly sampling the quadrats that are indicated

• After the samples are taken, statistics are utilized to estimate the population. This is what you will be doing.

Experimentation

• Done in a lab or field (field study)• Lab experiments – greater control of

conditions/variables. – Strength is that the likelihood of errors is

decreased and there are fewer opportunities for “contamination” or confounding variables.

– Drawback is that the environment is artificial.– Ex. Testing nitrogen concentrations on the growth

of corn plants in a greenhouse

Experimentation

• Field experiments – more accurate picture of how the subject organism interacts with their environment.– The drawback is that you often cannot control your

study’s environment .– It is exposed to factors that might alter the results of

your study (lots of unforeseen, uncontrolled factors). – Example: Mt. Pinatubo eruption in the Philippines and

the crash of the guanaco population in the Patagonia.

Modeling

• Some scientific questions cannot be easily answered through observation and experimentation.

• When this happens, scientists turn to models.– Usually computer or mathematical that describe

and model nature. – Models are useful because they allow scientists to

manipulate different model variables to see how organisms or whole ecosystems react.

Modeling Nature – Bison in Yellowstone

With the help of NASA, Yellowstone National Park has created a model that allows it to predict the movements of its bison during migration.

Modeling

• Models are built from real data taken in the field.

For example, satellite tracking data of elephants in Kenya is being used to create a model to study how ecosystem changes might affect elephant migrations and other population dynamics.

Modeling

• Before any model is used it is tested by inserting actual data to see if its predictions are accurate. – If a model is not predictive, then it is not useful.

• In the Yellowstone examples, ecologists have recreated Yellowstone as a virtual ecosystem that they can manipulate. – In the model they have included data on elk,

bison, bear, and wolf populations

Modeling

– The location of different vegetation such as meadows and forests.

– The amount of snow– The activities of geysers and other geothermal

landforms. • The combination of the data with computer

generated maps give scientists a powerful tool with which to create wildlife conservation plans and track diseases affecting the park.

Modeling

• Computer modeling was used extensively in planning for the reintroduction of grey wolves to the Yellowstone Ecosystem. – Models were used to see how the presence of

wolves would affect other species. • One source of error with models is they are

always simplistic, though they have gotten a lot better over the years!

Modeling a Meandering River

• http://www.youtube.com/watch?v=tndfTN64tkg&list=PLD0ADCF6B78E8AC0D

Learning Questions

• What are the five different levels of organization studied by ecologists?

• Describe the three general methods used by ecologists to study organisms?

• What ecological research methods would you use to study bird migration? Explain your choices.

• How might an ecologist use modeling to study fire in a forest? What might be some key variables used to create the model?