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Types of Scientific Investigation
Transcript of Types of Scientific Investigation
Sometimes, scientists are interested in things they can't observe themselves. These things are either too large, too small, too far away, or too difficult to get to.
For example, we can't get to the North Atlantic to count salmon, or to the bottom of the Penobscot River to count their eggs.
If a scientist is interested in something like this, he or she looks to find the data from observations that other scientists have made, scientists who are capable of observing things too large, too small, too far away, or too difficult to get to.
Since we are no longer the primary (or first) observers, we call our research with this data secondary research.
Now, It's Your Choice!
There are an infinite number of questions to ask, even just in environmental science.
How can you get your question answered?
What kind of investigation will help your team understand the topic you are interested in?
Time to choose.
In a field study, scientists go to where the environment is to observe it and collect evidence to answer their question.
There are three types of field studies:
In this type of investigation, scientists try to find how many of something are in the environment, or which type of living or nonliving thing is part of an ecosystem.
What different flowers are in our creek ecosystem?
This type of investigation is a preparation for a comparative or correlative study.
Descriptive Field Studies
Scientists use different methods of investigating situations that are interesting to them.
They also use a special vocabulary for their investigations, so they can understand each other, all over the world, from all different time periods.
Types of Scientific Investigation
In this type of investigation, scientists try to find out about populations (groups) of organisms or nonliving things in an environment over time or in different circumstances.
Is the stream warmer where it starts or where it opens into Messalonskee Stream?
Comparative Field Studies
In this type of investigation, scientists try to find a relationship between two parts of an environment. "Co-" means 'together,' and "relative" means connected.
If the stream is warmer at the mouth, does that mean there are more flowers there?
Correlative Field Studies
The control in a controlled experiment is an example of the subject in its normal, unchanged state.
Scientists use controls to compare the effects of changes on what is usual.
The control in the experiment about plants growing higher in warmer areas would be a set of plants growing in their normal area, with the usual temperatures experienced there.
Levels of Change
Scientists often need to narrow down the effects of changes on living or non-living things, so they use different levels of change.
For example, if we changed the temperature of plants, we could observe one set in a slightly warmer area, one set in a hot area, and one set in a cool/cold area. Those temperature changes are called changes in level.
We are going to change one variable on purpose. This is called the manipulated variable. Since we are the ones causing the change, and it's not in response to anything else, we think of it as independent. Independent means that it doesn't depend on something else.
The independent variable in our plant experiment is the different levels of temperature.
Just as we could have changed all different kinds of things about the plants, the response of the plants could be different in many ways:
size of leaves
speed of growth
We can only compare the sets if we look at one particular response. This responding variable is called the dependent variable. The effect on the plants is dependent on the change we made to the temperatures.
Analyzing the Data
Another trick to using secondary research is to make sure you know exactly what the data is saying. If you are looking to count Atlantic salmon and the data includes Pacific salmon, it won't help you.
Being careful to understand the other scientists' data is the only way to see if it can answer your question.
Which Data to Use?
There are lots of different places to look for data, mostly on the internet. The trick is to find data that was recorded by scientists who can be relied upon to be careful observers and recorders.
Often, these scientists work for universities, or the US or Maine government, or a non-governmental organization (NGO), like the David Suzuki Foundation or the The E.O. Wilson Biodiversity Foundation.
Check with a learning coach or Ms. McMahon to assess the reliability of a source.
Question and Data
When we have a question about something that we need secondary data to answer, we have to be sure the data we find can actually answer the question we have.
For example, if we are interested in the number of salmon in the North Atlantic compared to the number of eggs in Maine rivers in the past ten years, we couldn't use data from the 1900s, or egg data from one year and adult data from another year.
Work with your group to decide what kind of investigation will best answer your question.
What Do You Think?
How many in a set?
We will use sets of three or four while doing our investigations. We can't use just one example of the item, because one example of a living or non-living thing may not represent the norm for that thing.
For example, we may grow three plants to test the temperature effect just in case one of the seeds is a dud. Each change will be done to three separate plants, and the control will also have three plants.
The number of items in a set are called the
. We will do three trials for each level of change in our temperature experiment.
In this type of investigation, scientists set up a controlled set of items to observe. They carefully manipulate one level of change at a time to observe the response.
Do flowering plants grow higher in warmer areas?
A scientist named Francesco Redi tested the idea that rotting meat turned into maggots, which turned into flies.
He set up his
, open jars—the norm for his time.
were to use gauze and parchment on other sets of jars.
He kept the other possible variables in his experiment
, or unchanging.
Maggots and Meat
A variable is a thing that can change:
vari- means change, like vary
-able means able (can)
However, if everything that
change, we would never be able to figure out which change caused the effect we were observing.
If we changed the temperature, the amount of light, the amount of water, the type of plant, and the type of soil for each set of plants, and one set of plants grew higher, how would we know which of those changes caused the plants to grow higher?
We could have changed all kinds of things about the plants to observe the effects:
amount of water
type of water
timing of watering
amount of soil
type of soil
amount of light
amount of heat
type of pot
size of pot
number of plants together in one pot
We can only change one, to be sure that any effects we observe are due to that ONE change. The rest of these are held constant, kept the same for each set of plants.
If we can't find the data to use for our question, sometimes we have to adjust our question to the data we have available.
Use the data from observations other scientists made to answer a question you have.
Establish a control set, then change three other sets with one specific variable to observe the effects of those changes.
Going out into the environment
Finding relationships between things
When we report our data to others, we have to do it in a way they'll understand. We have to use measurements that others will relate to.
Decide what type of measure you will use:
Make sure you write your observations using this measurement unit.
And you MUST use metric measurements. These are the International Standard measurements, what all scientists use.