Friday, February 24, 2012

Follow up to the paper discussion: Reedy's students check this post out

Hi Mr. Reedy's students,

Great work tackling this scientific paper. Reading and comprehending these sorts of papers is always a challenge to start with, and gets easier with practice.  Remember that the authors anticipate their audience to be experts in the field, so that is why it may seem hard to read if you are just starting to learn about this stuff!

I really enjoyed reading your answers and you seem to be very much thinking in the right way.  I tell you what I was thinking about these discussion questions.

Discussion Questions.
3) In this experiment, the authors discovered that smaller male beetles were substantially better at finding females than larger male beetles, particularly at cool temperatures. However, finding a mate is just one part of this beetle's life.  Do you think it is always better to be smaller for these male beetles?  Can you think of other parts of a beetles life where it might be advantageous to be larger?  Do you think it is better for females to be smaller as well?  

My Answer:  Certainly there could be many life stages or situations where it is not advantageous to be smaller. Yessenia brought up a nice point about bigger females being able to have more offspring.  This is called fecundity selection- often larger females can have more (or bigger) offspring, which may increase their fitness.  Also, many of you recognized no predators were in this experiment, and predators may be able to attack smaller beetles better.  We don't actually know if this is the case, but could probably design an experiment to try and figure out.  Also, these beetles have something called nuptial gifts (the authors wrote about this in the beginning).  Males offer females a gift at the time of mating, and females like bigger gifts, and bigger males can make bigger gifts.  And do you know what the gift is?   Beyond just giving the female sperm at mating, the male ejaculate contains a nutrient rich substance that the female eats!!!!  Yep, females like to eat the male's large ejaculates, and it actually  helps them nourish their offspring!  Pretty awesome, huh!






Could spiders (or beetles) ever get this big???  Thanks to evolutionary constraints, they probably cannot!   As Mr. Reedy knows, spiders are not my favorite animals, so I am particularly grateful to these constraints for this reason.   He can probably tell you some good stories about my Arachnophobia...




4) Suppose that we went and found some beetles in their natural habitat, studied them for a year, and found that in every situation, it was better to be larger.  What do you think would happen over a very long time (many thousands of generations)?  Would we find beetles as big as a human some day?  

You guys came up with some pretty good answers to this one too!  If there is strong selection for beetles to be larger, they will evolve to be larger.  In fact, the authors had already artificially produced larger and smaller strains.  However, just because during one year, it was better to be larger, doesn't mean that it would consistently be better to be larger.  Maybe the climate in the year of the study favored larger beetles.  Or maybe the optimal beetle size is just slightly larger than they are now.  Then we would expect selection to favor larger ones until they reach this size, but then when they get bigger than the optimal size, selection would favor smaller beetles.   Julia brought up a great point, too.  She thought that the structure of the beetles exoskeleton might limit how large the beetle can get, and she is probably right.  You never find spiders or beetles, or many other invertebrates over a certain size, because of what we call constraints.  For example, beetles have very different respiratory and circulatory systems than mammals do, and wouldn't likely be able to support such a large body size with the limitations imposed by theses systems.  

Wednesday, February 22, 2012

Upcoming trip to Florida. Stay tuned!

 I am heading to Florida at the end of March to work on a evolutionary ecology project with Dan Warner and Aaron Reedy.  We will be studying sex-ratio selection, sexual selection, natural selection, and the population ecology of Brown Anoles. They are a really great animal to study and also look pretty sharp (see the picture at left by Dan). Check out this link to Aaron's blog to learn more!


http://wideworldscience.blogspot.com/2012/01/do-you-want-to-connect-your-classroom.html

Monday, February 13, 2012

Mr. Reedy's Students- Read this!


Hello Mr. Reedy's students!  You may remember me as that guy who came to your class to talk about turtles in December, or you may remember me as Mr. Reedy's BFF (I know are curious who Mr. Reedy's best friend forever is, and now you know).   You also may remember I am a scientist at Iowa State University, and that I work with a Middle School classroom in Des Moines, Iowa.  We are hoping that our classes are going to get to know each other, and share our science experiences with each other over the coming months.   

I believe that you are knee deep in your animal behavior studies at this point, and we would like you to read about an experiment with seed beetles published in a peer reviewed journal (check them out in the photo by CW Fox).  When scientists do research, they share that research through posters, talks, and through papers.  For a paper to be peer-reviewed, it means the paper was critically examined by other expert scientists. The paper could be published only after these other scientists approved of the experimental design, statistical analyses, and the conclusions drawn by the authors.   The paper we would like you to read is titled "Smaller beetles are better scramble competitors at cooler temperatures."

 Mr. Reedy should have given you a copy in class.  What I would like you to do is answer the following 4 questions.  Please write them as comments to this post!

Moya-LaraƱo J, M El Tigani El-Sayyid & CW Fox. 2007. Smaller beetles are better scramble competitors at cooler temperatures. Biology Letters 3: 475-478.  

Comprehension:
1) These authors designed an interesting experiment to help answer some questions they had.  After reading this paper, in your own words, write what question or questions motivated this experiment.


2) Figure 1A shows that most of the selection differentials are negative.  What does that mean?


Discussion:
3) In this experiment, the authors discovered that smaller male beetles were substantially better at finding females than larger male beetles, particularly at cool temperatures. However, finding a mate is just one part of this beetle's life.  Do you think it is always better to be smaller for these male beetles?  Can you think of other parts of a beetles life where it might be advantageous to be larger?  Do you think it is better for females to be smaller as well?  

4) Suppose that we went and found some beetles in their natural habitat, studied them for a year, and found that in every situation, it was better to be larger.  What do you think would happen over a very long time (many thousands of generations)?  Would we find beetles as big as a human some day?  

Friday, February 10, 2012

Exploring the different ways scientists work: Mt St Helens

We are in the Geology Unit, and took a look at one of the best studied volcanic eruptions of all time.

In 1980, Mount St. Helens in the state of Washington erupted.  In class today we looked at how scientists in two different disciplines studied the Mount St. Helens eruption.  A group of Geologists from the United States Geological Survey were very interested in the mechanics of the eruption, and why the mountain exploded the way it did.  The eruption eradicated almost all life in a 230 square mile area north of the mountain.  Ecologists were very interested in how plant and animal communities recolonized this lifeless, ash-covered area.  Neither of these scientist teams did experiments, but instead studied what  naturally happened, and learned a lot from it.  Read the post before where I clarify the difference between experiments and studies.



If you are interested in learning more about these studies, check out the links below.

Here is an account of the blast from the USGS.
http://www.youtube.com/watch?v=xP2dreOI8gI

This ecologist studied the change in plant and animal communities since the blast.
http://www.pbs.org/wgbh/nova/nature/crisafulli-blast-zone.html

Monday, February 6, 2012

State of the Union

Every year the President addresses Congress and the people of the USA in the State of the Union Address.  Last week we talked about sources of electricity and dependence on Fossil Fuels, so I thought it would be fitting to show the students what our President's energy plan was.   President's Obama's message was essentially that we want to increase domestic energy production of both fossil and renewable sources.  He suggested ending subsidies for oil, and putting that towards other sources.  Students were asked to critically think about President Obama's statement on energy, and write answers to several questions related to the topic.