Thursday, December 15, 2011

Scientists don't just learn from experiments!

If I ask students what a scientist does, they often answer "Do experiments!".  That is true of many scientists, but many great scientists have learned a lot without doing any experiment at all.  In my research I use experiments and something we call an observational study.
What is the difference between an experiment and a study?

Scientists often use controlled experiments and observational studies. There are many types of controlled experiments, but in general, the scientist will select a group of study subjects, randomly assign them to different treatments (or conditions where a variable is altered). It is important that the scientist is changing something about the conditions the study subjects will experience.   In an observational study, the scientist does not alter anything about the study subjects, but just makes careful observations and draws inferences.

Lets use an example to demonstrate the difference.  Suppose you have the question, Does temperature determine whether a turtle egg will become a male or female?  

Observational Study: You go out into the wild, and locate lots of fresh turtle nests from the same population, and monitor these nests until they hatch.  It would be best to record temperatures throughout the season within the nests, as well as other variables you think might be important (hydric conditions, soil pH, etc).  When they have hatched, you correlate the environmental variables with the sex ratio of the baby turtles in each nest.  Depending on what you find, you may want to repeat the study another year, or you may want to then further investigate these relationships in an  controlled experiment.
In the photo above, we are measuring various aspects of a natural painted turtle nest, as a part of a long term study started by my advisor Fred Janzen.  Who knew studying could be so fun!!  Photo by Brian Tugana.

Controlled experiment:  After collecting lots of turtle eggs from many moms in the same population of turtles, you can randomly divide the eggs from each mom into two treatments, warm and cool.   You set up two incubators at a cool temperature, and two at a warm temperature.  In this case, temperature will be the independent variable, or the thing the experimenter varies.  Then we need controls: all the eggs will be incubated in boxes that have the same substrate, the same water potential, the same amount of eggs in each box, etc.   After eggs hatch, you can see if the treatment (temperature) had an effect on the sex of the baby turtles.

To thoroughly answer this question, it would be best to do both this experiment and the study, as both give you different and important information.

Here we are measuring baby turtles in a lab.  These turtles were a part of one of my experiments! Most of this experiment took place in the field, but some parts happened in the lab.  Just because its an experiment, doesn't mean it needs to be in a lab.

Thursday, December 8, 2011

Why I study turtles!

I gave a research talk to Aaron Reedy's class this week on sex ratio evolution,  why I study the sex ratio in turtles, and I provided a case study on the topic from my own work.  Here is a bit of the background information about the theory that guides my research, and some slides that I shared with the high school students at Kelly High School in Chicago.
In many animal mating systems, one male can successfully produce offspring with many females.  In red deer for example, a single male fights off other males to gain mating access to a harem of females, at the exclusion of other males.  Females can only get pregnant once a year, yet males can get many females pregnant during the rut.    It seems as if the population could grow much faster if many more females were produced than males.

Yet, if that was the case, males would have much higher fitness than females, as they would be producing many more offspring.  In a situation with a female biased sex ratio, any females that could overproduce sons would have a huge fitness advantage, because sons would be able to have many more offspring than daughters.   We would expect this ability to overproduce sons would be selected for, and would drive the sex ratio towards unity.

Our expectation from sex ratio theory is that the primary sex ratio should be 50:50.

 Since turtles have temperature-dependent sex determination, rapidly changing climates can skew the sex ratio.  And turtles have been around for a very long time (turtles were around when dinosaurs were around), and have survived through many climate changes in the past.  There are several mechanisms by which turtles could adapt to changing climates, but I study how mom's nesting decisions may have played a role in adaptation to local climate.

I am working on writing up an experiment that shows mothers are maintaining a balanced sex ratio in the population by choosing specific places to lay their eggs.

Thursday, December 1, 2011

Going to Aaron Reedy's Class on Friday!

I am excited to go give a research talk at Kelly High School in Chicago this week!  I have collaborated with Mr. Reedy on some cool turtle and snake projects at our research site, "Turtle Camp" in Illinois. Along with other collaborators, we have worked to understand habitat use in hognose snakes. I have also helped him and Dan Warner  on a cool lizard project they have been working on in Florida.  Aaron has worked with the Janzen lab through the NSF Research Experience for Teachers program, and through the Turtle Camp Research and Education in Ecology (TREE) Program.   Aaron has proved to be a great collaborator in the field, so now we are going to start a collaboration between classrooms!  We are designing a science project which both Mr. Morris' and Mr. Reedy's classroom will engage in together.  Look for an update on how the day in Mr. Reedy's class went!

Check out Mr. Reedy's inspirational talk here:

Wednesday, November 30, 2011

Plant Germination Experiment: Part III

This week in class we worked on writing the discussion section for the plant experiment.  Over the three weeks of this project, students set up the experiment, graphed the results (which coincided with graphing in Math) and now we discuss our results in a assignment that will be graded both in our science class and in their Literacy class. 

Students recognize that scientists need to be well rounded, and that the lessons they learn in their other classes like Math and Literacy, are fundamental to success in science.

Here is an example discussion a 7th grade student wrote in class:

“In this experiment we studied how salt in water can affect corn and radish germination. This was important to study because farmers depend on germination of their crops to live, and we depend on some crops to eat and get everything we need to survive. We set it up by putting 5 corn or radish seeds in a petri dish with water that has different amounts of salt. What happened was the radish seeds germinated faster than the corn. But nothing grew in the 3.5% salt dish and the 0.5% salt grew fastest. The 1% salt corn had all 5 seeds grow, the 1% radish had about 1 dead seed we think because the last day of this experiemnet one seed was covered in mold. The results mean salt can effect germination and too much can kill a plant, but I think a little salt might be good. I think I would try growing different plants with this experiment, maybe just corn and radishes are the only plants whose growth is affected by salt but maybe not”

Plant Germination Experiment: Part II

Students have collected data every other day on their plant germination rates for the last week.  Now we started graphing the data.  We decided to use line graphs, which coincides with the curriculum in Math Class.  They had learned how to do Line graphs earlier in the week, and now were able to apply their knowledge. Although we started graphing the data, there is still one more week of data to collect.  Every other day, student will check their experiment, and add data points to the graph.

Plant Germination! 10/28

We have been very busy in class recently.  We undertook a three week plant germination experiment.  Students wanted to see how salt influenced germination rates in two plant species that are used for human consumption.  Corn, which Iowans are very familiar with, and radish's.  There are many places around the world where salinity is a major problem for crop lands, and if lands aren't properly managed, soil can be inhospitable to crop growth.  Australia is a great example, as removing native vegetation and irrigating has drawn up salt from well below the soil.   We designed a simple experiment to see how different salinity levels influence germination, and to see if both species responded similarly.

Pictured here is our experiment.  Each petri dish has 5 seeds of radish or corn.  2 species x 4 treatments, replicated by 6 class periods.

Wednesday, October 5, 2011

Peter Benson's Message is a good one!

A good family friend, Peter Benson passed away this week.  Peter had a great career as the president of the Search Institute and encouraged parents and educators to focus on children's strengths, not weaknesses!   People in education everywhere can learn a lot from his work!  See the video to learn about Peter's message.  Rest in peace, Peter.

Bacteria Lab- Part 2

Students found that EVERY location they tested had bacteria present!  Also, after quantifying bacterial growth we had very convincing evidence that the bacteria sampled grew much faster at 37C, (the same temperature as the human body), than at 4C (an average refrigerator temperature).   We used clear grids placed over the petri plates, and counted how many squares had bacterial growth present in them. Students calculated the average percent of squares with bacterial growth from the two temperature treatments, and made a bar graph to visualize their data.  We then discussed how to interpret our results.  Do bacteria always grow faster at warmer temperatures?  Is there an upper temperature limit where bacteria can survive?  Based off of our results, can we conclude bacteria are absolutely everywhere?  Or is it safer to conclude that bacteria are likely to be found in most places around our school?  We also took some video from class this week, so hopefully we can share that soon!

You might wonder how this is at all relevant to my turtle research. Abiotic conditions (such as temperature, moisture, etc) are important for all organisms.  One major concern with turtles is that climate change will influence population growth by altering the population sex ratio, because the gender of developing turtle eggs is determined by the temperature.  To this end, population growth of both turtles and bacteria may be directly influenced by temperature, although our ability to see this effect in turtles takes much longer. 

Friday, September 30, 2011

Why we refrigerate: Temperature-dependent bacterial growth.

Today in class we began an experiment to explore bacterial diversity, and assess the influence of temperature on bacterial growth.  Students were give cotton swabs and petri dishes, and asked to make bacterial swabs in much the same way as a doctor tests for strep throat.  Students chose a location to test, and made two samples from the one location.  One of the samples was placed in a refrigerator, and the other in a warmer incubator.  On Monday, students will quantify bacterial growth, and pool data to make graphs to answer the question "Does temperature influence bacterial growth?"  Students will also get to see the diversity of growth forms and the broad environments bacteria inhabit.

Friday, September 23, 2011

9/22  We continued to develop Science fair questions and started working on developing hypotheses.  I found a great activity that the students very much enjoyed, and helped them better understand the process of science.  Click the link below!

Science Fair!

9/16-  Students brought in Science Fair questions, and we talked about sorts of questions are scientists able to answer, what qualities make a good questions, and talked about how one might go about answering questions.

Observation skills

This week I brought 3 species of hatchling turtles into the classroom- map, snapping and painted turtles.  Each pair of students was given a hatchling and required to make qualitative and quantitative observations.  Measurements and sketches of the carapace and plastron were made, as well written descriptions.  Part way through class, we mixed up turtles and descriptions, and their classmates tried to identify the turtle from the description.  We then critiqued what observations were most helpful for making the correct identification, and showed field guides (bird, reptile and insect guides) as a model for how these descriptions are  made by professionals.  Students loved getting to see the live turtles, and I think it helped them understand the importance of accurate, detailed note-taking.

Thursday, September 8, 2011

Sunday, September 4, 2011

  This week, students shared their conceptions about the field of science and what scientists do.  I was able to more formally introduce myself to them by talking about my scientific background and the various projects I have worked on and places I have been as a scientist so far.  Here is a link to some photos showing my past and present research.

Friday, August 26, 2011

First Day of Class

Yesterday I was in Mr. Morris' class for the first day of school to meet the 7th graders taking his science class.  No discussion of rules or syllabus for the first day of Mr. Morris' class; we went outside to identify living and non-living things, and students were challenged to think about what characteristics define life.