Weekend Science Fun: Classification of Organisms

After talking about relatives of insects a few weeks ago, I realized that maybe we needed to take a step back and define the words I was using, like phylum. These are common terms used in biology, but it isn't always easy to remember how they relate to each other. Let's take a look at how scientists put living things in groups.

The science of organizing living things into groups is called classification. The Swedish botanist Linnaeus first proposed a system for grouping and naming organisms in the 1750's. The system is hierarchical with the upper levels including those below it.

If you are older, you may have learned something in school like "King Philip Came Over From Greater Spain" to remember the hierarchy of groups. Recently scientists have added a higher level, the domain and removed the Kingdom Monera. Plants, fungi, animals and protists belong to the Domain Eucharya.

This video explains the domains:

The kingdoms contains many distinct groups called phyla. Each phylum is divided into a number of classes. The classes are further divided into orders, families, genera, and finally, species.

Here is the classification hierarchy of the honey bee:

Domain:  Eucharya
Kingdom Animalia
Phylum Arthropoda
Class Insecta
Order Hymenoptera
Family Apidae
Genus Apis
species mellifera
Common name: honey bee

Sometimes it can be difficult to visualize. If you are a visual person, try drawing some diagrams. Here's one for insects.

Classification Activities for Children

Up until recently, classification was mostly based on the physical characteristics of the organisms.

1. Sorting is an important precursor for classification for very young children.

Gather:

  • toys, balls, stuffed animals, etc.

For young children, sort by any feature you can think of.  You can sort by color, soft versus hard, shiny versus dull, by size. It's a great way to learn opposites, colors, shapes, and vocabulary words, too. Have fun!

Later graduate to sorting various toy animals by classes. Although is is best to use realistic models or stuffed animals, you can use pictures as well.

Start with the vertebrates, the  fish, birds, reptiles, amphibians and mammals.What characteristics do fish have? (fins, scales, gills). How is a reptile, such as a snake, different from an amphibian, like a frog or salamander? (Dry skin, scales). How is a bird (with feathers and a beak) different from a bat (mammal)?

Once your child masters that level, add insects, spiders and other animals without backbones. You may also sort by other characteristics, such as carnivore (meat eater), herbivore (plant eater) or decomposer (eats dead plants). Make a box labeled with each characteristic for the child to place the objects in or simply make heaps on the floor.

What are some differences between the plant and the butterfly sitting on it?

2. Twenty questions

The guessing game “twenty questions” also can be modified to act like a classification key. Keys are used to identify living things and often utilize similar yes or no questions.

Have one person think of an object, preferably a living thing in this case. The point is for the others to ask yes or no questions, using narrowing the topic until someone can guess what the object is. The trick is that you are only allowed 20 questions.

Is it living or dead? Is it green? Does it have flowers? Does it have a backbone? Does it have feathers? Does it have scales? The characteristics that separate the kingdoms, phyla and classes can quickly narrow your focus to the correct group.

3. Build your own classification scheme.

Gather:

  • bag
  • paper clips
  • small balls
  • crayons
  • chalk
  • coins
  • pencils

To explore ways to classify things, have your children build their own classification scheme using objects from around the house. Fill a bag beforehand with a mix of items similar to those suggested above. Ask the children to group the objects. What characteristics did they use? Would the balls and coins go together because they are both round, or did the coins go with the paper clips because they were metal? Name the groups, and then mix the items again to come up with another system.

One of the fun parts of classification is that there aren’t any right answers, just best guesses. Scientists rearrange the groups all the time as they gather more information.

4. Older children may want to investigate the use of DNA to group and identify living things.

 

For more information try:

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