Population Ecology Lab: Estimating Population Size

I have always found it difficult to find quality labs to use with my students when teaching my units on ecology. My school is on a busy city street, we have no access to a pond or woods, and only very limited access to grass in the school yard! Therefore, any labs we do in ecology have to be labs that can be carried out within the classroom or within the laboratory. One lab that works really well in my population ecology unit is "The Wild Bean Population."

In order to effectively study living organisms, scientists often need to know the size of a given population. A population is a group of organisms of the same species that live in the same general area. It is not reasonable to think that every individual in the population can be counted, and it is often difficult to get an accurate estimation of population size since organisms tend to hide, move around, etc. 

Population biologists have developed several methods for sampling a population. In this lab, you will use the sampling technique known as “the mark and recapture method” to estimate the size of a population of wild beans! This method involves "capturing" a number of individuals from a population, marking or tagging them, and then releasing them back into the wild.   

Anyone can do this lab since it uses very simple materials! All you need is dry white navy beans, dry red pinto beans, and a brown lunch sack.

The white beans represent the population of wild beans that lives within the brown paper sack. Students grab a handful of beans and remove them from the sack. This represents the initial capture of organisms. The white beans are counted, marked and returned to the sack. 

The easiest way to do this would be to have the students mark each bean with a Sharpie before returning it to the sack. I teach 5 biology classes, and did not want to have to throw away that many marked beans at the end of each class. My solution was to have the students replace the white beans from the initial capture with red beans. The red beans represent organisms that were initially captured and returned to their environment.

At a later time, a second capturing is conducted. Some of the organisms in the second recapture were previously marked while others in the second recapture will have no mark. If you know the following information: (1) The number of individuals initially marked, (2) the total number of individuals recaptured in the second group, and (3) the number of marked individuals in the second recapture, it is possible to make an estimation as to the total population size.  

This lab satisfied three objectives:

• To learn the “mark and recapture” technique for estimating the size of a population.
• To calculate the size of a population from given data.
• To make predictions about the size of a population under various conditions.

I generally do not like "simulation-type" labs such as this one, but I am always very pleased with the results and the concepts that my students learn from this lab. The students are able to carry out mathematical calculations to determine the population size, and calculate their percent error. The final analysis questions are thought provoking and require critical thinking skills. All in all, this has all the components of a great lab activity.

The Wild Bean Population

We Stop for Turtles!

Today after school, my daughter and I were driving home.  As we turned onto a very busy street, we noticed a VERY LARGE turtle topple off the curb and into the street.  The poor guy landed upside down!  I need a bumper sticker that says "I brake for turtles!"  We stopped and picked up the turtle and put him in our car.  We released him into our pond, and I hope he lives happily ever after.

Science Illustrated: A Great Resource for the Classroom!

I NEVER want to see this look in my class!!

And I am sure that you do not either.  I am constantly on the look out for tidbits of new and/or interesting science news to use in my classroom.  My students look forward to "Hey guys, did you hear about "blah blah blah" on the news?"  Or,  "Hey guys, look at this cool video I found!"

This does not distract from the objectives of the day, and it only takes just a few minutes.  But the pay-off is huge in terms of student interest in my class.

One of my favorite sites for information is Science Illustrated online.  The news is current, fun, exciting, and most importantly....not too lengthy!!  I love that there is a wide range of areas to choose from:  Science, Nature, Technology, Space, Culture, and Medicine.

You will find a wide range of articles, glorious and interesting photographs and short video clips.

Have Fun Teaching!!

Do you love Pinterest?

Are you a Pinterest addict yet?

If you have not taken a look at this site yet, then don't delay!  Head that way right now.  Pinterest is the latest craze and people are pinning like mad.  What are they pinning?  Just everything under the sun, from recipes, to clothes, to science products (!), to favorite books and movies.  Pinterest is like a huge bulletin board.  If you have something you like, you can pin it to a board that you have created.

I hope that you will check out all of my boards.  Most of my boards are related to teaching science and you will find some great teaching materials there.  I have also found some terrific recipes on Pinterest and have pinned them to my "recipe" board.  The chocolate souffle recipe I found is to die for!

Check out my pin boards here:  Science Stuff on Pinterest!  I would love for you to become one of my Pinterest followers.

Science Skills: Using Graphic Organizers to Master Science Information

We all know that the volume of information in a science textbook is overwhelming for many of our students.  Take time at the beginning of the school year to teach some simple skills to help your students learn to organize the information into a manageable form.  We have a saying in my classroom:  "Be the master of the information.  Do not let the information master you."

With just a little direction students can learn a few techniques that will help them master the information all year long.   Science is so orderly and logical that the use of graphic organizers as a study technique makes perfect sense.  There are many different types of organizers, but the ones that work best for me are concept maps, event chains and cycle maps.

At the beginning of each year, I take the time to teach this important skill to my students.  I give them passages to read and then we practice organizing the information using either a concept map, an events chain or a cycle map.

At first I give the students a diagram to fill in, such as the one seen below:

But very quickly I have my students designing and drawing their own concept maps.  Once students get the hang of the technique, many of them find it to be a fun and enjoyable way to study!

Graphic Organizers: Tools for Mastering Science Concepts