STEM Club: Scientific Classification and Dichotomous Keys

I started teaching a new class – live and in person for my local homeschool community.  I am very excited to teach formally again and this format promises to be both very rewarding and very challenging.  Rewarding because I get to share my passion for science with a great group of middle level students – such a fun age!  Challenging because as a homeschool mom, I do not have a class set of materials and equipment as I did in the public school and the kids vary in age and ability.

The course I have outlined for this first trimester focuses on life science.  We will be covering everything from scientific classification, cell structure, food chains and webs, and biomes.  There is so much to cover that another challenge will be simply deciding what to include.

levels of classification foldableScientific Classification

In our first session, I introduced the topic of scientific classification and how to use a dichotomous key.  Here is a simple video by Mark Drollinger explaining the six kingdom system:

▶ Six Kingdoms of Classification by Mark Drollinger

There are 3 Domains – Bacteria (prokaryotic micoroorganisms), Archaea (single-celled microorganisms), and Eukarya (organism whose cells contain a nucleus and other structures (organelles) enclosed within membranes).  Domains can be further divided into Kingdoms.

Currently, there are 6 Kingdoms – PlantsAnimalsFungiProtistsArchaea, and Bacteria.  Note that some resources show 5 Kingdoms (Plants, Animals, Fungi, Protists, and Monera) – grouping Archaea and Monera together.

Each of these kingdoms can be further divided into Phylum, Class, Order, Family, Genus, Species.  Some resources will show more specific levels including (but not limited to) superorders, subfamilies, tribes, etc.  For the purposes of this class, we will be using the levels shown here in bold and underlined.

If you have a BrainPop subscription, you may also wish to see the video on  Classification.

Dichotomous Keys

After a brief introduction and Power Point presentation on scientific classification (I could have been more concise than I was, actually), I introduced dichotomous keys.  Dichotomous keys are a tool that is used to identify organisms and that consist of the answers to a series of questions.

Here is another video by Drollinger that illustrates how these tools are used:

▶ Dichotomous Key by Mark Drollinger

Working in small groups, the kids each removed one of his/her shoes and placed it on the table.  They then carefully examined each shoe, noting its characteristics. They then brainstormed two categories into which each shoe either fit or did not fit; thereafter physically dividing the shoes into the two categories.  They continued in this way until 

each shoe stood alone.  They then recorded their dichotomous key on butcher paper and shared it with the class.  One group (which ended up splintering into two due to creative differences) chose to take the assignment further and rather than create a key for shoes, made one for the popular game, Minecraft. As I’d anticipated, they weren’t as successful with this but I loved their passion and commitment to see it through.

As it was clear that some groups understood and some did not – I took them outside and began to walk them through identifying one of the trees nearby using a dichotomous key from a book I’d brought along, Trees to Know in Oregon by Edward Jensen.  Though I live now in California, this is one of the best field guides I have ever come across.  I highly recommend it to anyone in the Pacific Northwest.

For many of the kids, it was clear that they hadn’t had much experience looking at the characteristics of trees.  This real-time assessment provided me with a clear direction for our next session when we will be focusing upon plants.

scientific classificationFoldable

For homework, I asked the kids to create a flip book or foldable for their interactive science notebook.  We had a little trouble creating one from scratch in class that I did not anticipate.  I’ve thereby created one and provide it to you for your personal use – Levels of Classification. The photo collage at the top shows the sample I used in class. The graphic just above shows the foldable I created.  It is designed to open like a mini-book so you’ll want to download the PDF to get both pages.

  1. Print it out front/back
  2. Fold it in half hamburger style (the short, fat way)
  3. Cut along the black line between the classification levels on the front flap only
  4. Choose an animal (or plant) and write the name on front cover in upper left corner
  5. Research the taxonomy of your selected animal (or plant)
  6. Beneath the flap, write down the characteristics that are true of all those animals (or plants) at that classification level (the first level – Domain – is done for you). Feel free to draw little pictures to help you remember these characteristics.

I would love to see your kids’ work when they have finished.  Please post a link in the comments or feel free to email me a digital picture of their work.  If I get enough submissions, I’ll create a little slideshow. 🙂

Entomology Week #3 – Insect Survey for Kids (w/ Free Notebooking Page)

As a part of the Introductory Entomology course we are undertaking this month, we took advantage of the long weekend to do an insect survey in our backyard.  We headed out with a homemade transect device (four 1-meter length PVC tubes connected with L-joints to form a square) and a butterfly net.  We had high hopes that we would find a variety of insects as well as numerous different orders.  Be it due to time of day or season, this is not how it turned out.  Either way, we did make a discovery.

We had observed two very similar insects while undertaking our survey and it lead us to ask a number of questions.  Are they the same species?  Is one male and the other female?  What do they eat?  As we sketched and researched the answers to our questions, I was tickled to discover they were two distinct species … Milkweed (Lygaeus kalmii) and Western Boxelder (Boisea rubrolineata).  The majority of the bugs we observed were Milkweed bugs, I therefore share some of the facts we learned about them here.

Edited 26 Feb 2014 – I wonder now if some weren’t Bordered Plant (Largus succinctus).  I’ll have to take pictures and investigate this further.

insect survey

True Bugs

Milkweed and boxelder bugs are true bugs (order Hemiptera); beetles, moths, flies, and butterflies are not. Bugs have the usual complement of structures that they share with just about all other insects: six legs, three body parts (head, thorax, and abdomen), and two antennae. Hemiptera do not have mouths for biting and chewing food—they have a tubelike beak for sucking fluids. The milkweed and boxelder bugs suck nutrients from seeds.

Milkweed BugLife Cycle Changes .. Simple or Complete?

Hemiptera go through simple metamorphosis. The insect emerges from an egg looking like a tiny version of the adult, with slight differences in body proportions and incompletely developed wings. The immature bugs are called nymphs. As with all insects, in order to grow the nymphs must molt periodically. Just after molting the bug is creamy yellow with bright red legs and antennae. Within a few hours the body turns dark orange, and the legs and antennae resume their usual black color.

milkweed instar

Hemiptera go through five nymphal stages (instars) as they mature. Each molt produces a larger nymph that is more completely developed. As they grow, the dark wings appear on the backs of the bugs as black spots. Other black markings start to appear and eventually develop into the characteristic patterns of black and orange. The last molt reveals the adult.

Male or female?

Milkweed bugs continue to feed as adults, inserting their long beaks into seeds to suck out oils and other nutrients. Mating is easily observed, as the two mating bugs remain attached end to end for an extended time. It is possible to distinguish female and male adults by body markings. Look on the ventral (belly) side of the bugs. The tip of the abdomen is black, followed by a solid orange segment (with tiny black dots at the edges). If the next two segments following the orange band have solid black bands, the bug is a male. However, if the segment following the orange band is orange in the middle, making it look like it has two large black spots on the sides, followed by a segment with a solid black band, the bug is female. Males tend to be smaller than females.

insect order printableWhile our insect survey didn’t reveal the diversity we expected, we did enjoy the experience. We had selected four different sites – the grassy hillside behind our house, a rocky area, in the shade beneath the Oleaders, and in a drainage ditch.  We observed the greatest number and variety in the cooler areas.  The kids thereby made a hypothesis that they would see a greater number and variety in a cooler time of day or season.  We look forward to doing this activity again to test their theories.   I’ve created a free  insect order notebooking page for my valued readers.  Please feel free to pin it and share it with friends.

As the summer progresses, we look forward to doing additional insect surveys.  We have talked about also setting up a few pitfall traps and a Berlese funnel.  These collection devices, as shown in my Introductory Entomology Unit Study eBook, are bound to yield greater numbers of insects.