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Spring cleaning in your biology closet March 04 2020, 0 Comments

It’s that time of year when the urge to put things in order can strike. You may have a closet with a lot of biology materials that you want to evaluate. Here are my suggestions for things to throw out. You may not want to discard the whole material just because it has flawed content provided it is feasible to fix the problems.

In the animal kingdom materials, if you find anything that has the phylum Coelenterata, please remove that name or cover it. Biologists haven’t used it for more than 30 years. That phylum was split into two others when biologists discovered that it held two unrelated groups. The two lineages are called phylum Cnidaria (anemones, corals, and jellyfish) and phylum Ctenophora (comb jellies). It is likely that you can cover over “Coelenterata” and add the label “Cnidaria.” Just make sure that you don’t have comb jellies in with your cnidarians.

Another no-no for the animal kingdom is showing protozoa along with the animals. This goes back to the two-kingdom idea of classification, and biologists and biology textbooks haven’t grouped protozoans with animals in more than 40 years.

If you find a chart that is labeled “Non-Chordates,” change the title to “Invertebrates.” Maybe “non-Chordate” was useful in the past, but biologists use “invertebrate” far more often. I searched books on Amazon.com using “non-chordates,” and I got six titles, all published outside the US. I searched “invertebrates,” and got over 6000 titles. A non-chordate chart isn’t likely to show current information, so it is time to recycle it or at least recycle the images and add new text.

The relationships between the phyla of animals solidified about 15 years ago. In biology, classification has morphed into systematics, which all about relationships and shared common ancestry. The details of this would take several blogs so I will simply say that the arthropods are related to the nematodes, and the mollusks are related to the annelids. Arthropods were once grouped with annelids, but that is no longer considered valid. Can you add something to your animal kingdom chart that shows which phyla are closely related? See my book, Kingdoms of Life Connected, for help if your animal kingdom chart needs a redo. https://big-picture-science.myshopify.com/collections/frontpage/products/kingdoms-of-life-connected-second-edition.  It is also available as an ebook (pdf).

Dig back into the cobwebs in the botany section of your closet. If your chart of the plant has club mosses separated from the fern clade – whisk ferns, horsetails, and ferns – you have a good representation of life’s diversity. The chart from InPrint for Children is a good example. https://big-picture-science.myshopify.com/collections/montessori-botany-materials/products/plant-kingdom-chart . Another mark of a current material – it should use the term “eudicots” instead of “dicots.”  If your chart has phylum names, it is quite possible that many of the names are obsolete. Many botanists no longer use phyla or division names. Instead, they use lineage names, and sometimes a common name is all you need. I have a graduate level botany textbook that uses no phylum/division names. 

If your plant kingdom chart has fungi or bacteria on it, the time has come to do some serious pruning. Those two have to go to their own charts. If the image of a fungus appears on a plant kingdom chart, that’s what children will remember even if you say that it doesn’t belong there. The fungus kingdom is a sister to the animal kingdom. In nature, fungi and plants are partners, but on classification charts, they shouldn’t hang around together.

If you have a Five Kingdoms chart, file it under the history of biology. It should NOT be the first thing children see as they study the diversity of life. The Tree of Life is the place to start.

How about your timeline of life? This is a difficult material to do well, and there are many bad attempts out there. Does your timeline show several red lines coming together (converging)? That’s the traditional style, but lineages do not converge (fuse together); they diverge (split apart). Maybe you could salvage the images and redo the timeline without the misleading lines. Check the dates for the fossils because there are several in the wrong place on the older timelines.

Does your timeline of life have photos of extant animals or plants in prehistoric times? This gives a very wrong impression. I’ve seen a timeline that had “First marsupial” and a picture of a kangaroo. This is just like saying “First eutherian (placental) mammal” and showing a picture of a horse. Both the kangaroo and the horse evolved within the last few million years. They are both adapted to live on grasslands and open shrub lands, where resources are spread out, and there is little cover from predators. Therefore both are good at moving quickly over long distances. Neither one of them belongs in the Mesozoic Era on a timeline of life. Mesozoic mammals were much smaller and less specialized.

Does your timeline have the five major extinctions? And does it have ice ages in the right places? The older charts used ice to symbolize all extinctions, although that wasn’t the cause in most of them. The five major extinctions come at the end of the Ordovician, Devonian, Permian, Triassic, and Cretaceous Periods. They are such important shapers of life that they are essential to a good timeline.

If all this correcting sounds like too much to do, remember that you are doing it for the children. They need current information and a foundation that they can use in their future studies. There is no point in giving them science “information” that they will never see outside a Montessori classroom.


An imaginary tour of nesting boxes for the plant kingdom December 13 2019, 0 Comments

The nesting boxes for the plant kingdom are a classic Montessori material. (They are usually called Chinese boxes, but I don’t like to use that term. They certainly didn’t come from China.) Like many other materials that were created many years ago, this one needs a make-over or at least a reality check to see if it reflects what children will see in their later studies.

Paraphrasing a Chinese proverb, if your nesting/Chinese boxes are based on a two-kingdom classification, and they contain the bacteria and fungi, the best time to change them was before 1980. The second best time is now.

The point of elementary studies isn’t to teach children names and ideas that they are not likely to see again. Maria Montessori said that children who complete her elementary program would have acquired knowledge equal to a high school student of her day. She wasn’t trying to create a separate set of biology terms; she was giving children the mainstream academic knowledge of her day. Continuing to use the terminology and concepts of the traditional lessons without checking to see current academic view leads to problems. Children may have to discard their Montessori lessons and go back to the beginning to learn contemporary biology. “Unlearning” is very hard for people. They tend to cling to the first way they learned something, and they must accept that their version is wrong before they can accept another view.

If there were nesting boxes that reflect the current academic view of the plant kingdom, how would they look? Here are my ideas.

Picture a large, green box that is labeled “Plant Kingdom.” It could have other labels as well as that main one. Possibilities are the more formal Latin Kingdom Plantae, or the more descriptive one, Embryophytes. The latter is the informal scientific name for land plants.

We take the lid off this box and find a small box labeled “Bryophytes, the nonvascular plants” and a much larger one labeled “Tracheophytes, the vascular plants.” Inside the bryophyte box, there are three smaller boxes labeled “hornworts”, “liverworts”, and “mosses.” Should there be a label for the division/phylum of these boxes? There doesn’t have to be. I have an advanced botany textbook that doesn’t use a Linnaean rank name for these branches of plant life. If you want to add the division/phylum names, see Wikipedia. It is generally quite good for plant classification. 

The larger Tracheophyte box contains two boxes, a small one labeled “lycophytes” and a much larger one labeled “euphyllophytes, the true-leaf plants.” The lycophyte box has three small boxes inside, the club mosses, spike mosses, and quillworts. Alternatively, the lycophyte box could list these three lineages on the lid and not separate them. They are best described as orders of the lycophytes.

The euphyllophyte box has two boxes inside, a smaller one labeled “fern clade, the monilophytes” and a larger one labeled “Spermatophytes, the seed plants.” The fern clade box has several smaller boxes. They are labeled: “ophioglossids – whiskferns, alder’s tongue ferns, and grape ferns”; “equisetums – the horsetails and scouring rushes”; and “leptosporangiate ferns or polypod ferns – the true ferns.” If your school is in a tropical climate, you may need to add a fourth box for the marattid ferns. They are huge plants that grow only in the tropics.

The spermatophyte box holds two boxes, the angiosperms or flowering plants, and the gymnosperms, the naked seed plants. The gymnosperm box holds four boxes – the cycads, the ginkgo, the conifers, and the gnetophytes. It is uncertain at present whether the gnetophytes belong in their own separate box or within another of the seed plant boxes. It is clear that they do not belong in the angiosperm box, however.

The angiosperms or flowering plants must have a big box. They make up about 90% of the plant kingdom. There are several boxes inside their box. A couple of very small boxes hold the first branches – the water lilies and the anise tree. Then there is a small box labeled “magnoliids,” a medium box labeled “monocots,” and a large box labeled “eudicots.” Three-quarters of the flowering plants are eudicots; about 22% are monocots.

All this can be imagined, but it will take quite some creativity to make physical containers that can actually hold an image and information about each of these branches of the plant kingdom. The information should include the lineages of the plant. For example: Sunflower lineages – embryophytes, tracheophytes, euphyllophytes, spermatophytes, angiosperms, eudicots. The text should also give some of the defining features – the derived traits – of each group.

If you need the illustrations or more information, see https://big-picture-science.myshopify.com/collections/montessori-botany-materials/products/the-plant-kingdom. This is a pdf of a PowerPoint for teacher education. You can print the images for use in your classroom. It has all the images you need except quillworts. Those lycophytes are rare, and the main reason to include them is that they are the closest relatives to the ancient Lepidodendron trees.

Please let me know if you need help or have questions on plant kingdom nesting boxes. If you want to have another set for the flowering plants, that’s a more involved story. It would be fun to do, however.

Happy plant explorations,

Priscilla


How do you divide the eukaryotes? September 19 2019, 0 Comments

If I asked you how you would divide the eukaryotes into groups, what would you say? Many people would say protists, fungi, animals, and plants. This is the idea presented in Five (or Six) Kingdoms classification. There is a more enlightening way to divide the eukaryotes, one that students currently see in introductory college courses.

The DNA revolution and the development of systematics rather than plain classification have given us a new view. Systematics includes the relationships between taxonomic categories instead of listing them with no information about their shared ancestors. It is a young science that has produced many changes and will likely produce many more.

This is not to say that we don’t have useable information right now. The largest categories of eukaryotes have been defined, and they are called the eukaryotic supergroups. There are four of them presently, and so the eukaryotes can be divided into four groups. Here’s an introduction to the archaeplastida, SAR, excavata, and unikonts aka Amorphea.

Archaeplastida is the lineage that acquired the first chloroplast. Its name means “ancient plastids.” A plastid is a type of organelle in a eukaryotic cell, and the category includes the chloroplast, whose name means “green body.” The archaeplastida lineage includes red algae and green algae, along with the embryophytes or land plants, which evolved from a green alga. This lineage is the only one that incorporated an ancient cyanobacterium into its cells. The origin of the chloroplasts in other lineages is a more complicated story.

 

The SAR lineage is named for the three main branches within it, stramenopiles, alveolates, and rhizarians. These lineages were defined independently and then researchers gathered enough evidence to conclude that they share a common ancestor. The stramenopiles (aka chromists or heterokonts) include brown algae, golden algae, diatoms, and water molds. Alveolates include dinoflagellates, apicomplexans (parasites such as malaria), and ciliates. The rhizarians include foraminiferans and radiolarians, single cell organisms that build amazing outer shells called tests.

 

And where did these branches of life get their chloroplasts? It seems that chloroplasts are NOT easy to acquire. Apparently, it is easier to take one from another cell than to acquire one by eating a cyanobacterium. An ancestor of the stramenopiles and alveolates probably ate a red alga and kept its chloroplasts. Euglenas, which we meet below, got their chloroplasts from a green alga.

The third eukaryotic supergroup is the excavata, also called the excavates, but I see potential for confusion between the word as a noun vs. a verb. The lineage is named for a groove that looks like it has been excavated from the cells of some members. The excavata include the euglenas, which are free-living, and the trypanosomes, which are parasites. Other members of this group include the parasite Giardia and organisms that live in the guts of termites and help them break down cellulose. These have reduced mitochondria, so small that they were first described as lacking mitochondria.

 

I know you have been waiting for the last of the four supergroups, our own lineage, the unikonts (“single flagellum”) also known as the Amorphea (“having no form”). “Wait a minute,” you may be thinking, “we definitely have form.” The amoebas that belong to this lineage do not, however. The Amoebozoa lineage includes most of the slime molds or social amoebas as well as the single cell ones. Some of the latter build hard coverings (tests) for themselves. The other members of the unikonts are the fungus kingdom and the animal kingdom, which are sister kingdoms, having shared a common ancestor right before they branched off. There are other single cell organisms that are related to animals and fungi as well.

As you can see, the old protist kingdom had many different lineages of life shoe-horned into it, and the kingdoms that developed from its members were chopped off and boxed separately from it in the Five (or Six) Kingdoms scheme.

Why should you or your children learn about the supergroups of eukaryotes? It gives you a richer view of life and one that your children will see in their future studies. Will the names stay the same? Maybe, or maybe not, but these are the names in current college biology books, and it is worthwhile to learn about them and their members now.  

Enjoy your explorations of the living world!

Priscilla 


What goes on a plant kingdom chart? December 27 2018, 0 Comments

Like its counterpart, the animal kingdom chart, all Montessori elementary classrooms need a plant kingdom chart. A current version of this chart will have the same elements as a traditional one, but the groups will not have the same labels or arrangement as they have had in decades past. DNA studies and phylogenetic systematics have changed the look of the plant kingdom, and our charts need to reflect this. It is hard to find a solid consensus among botanists on the “right” names, but that is no excuse for giving names that we know are obsolete.

I’ve listed my recommendations for contents of a current plant kingdom chart below. The names that I think are most important are in boldface type. The other names may also be useful. Ask yourself, “Will elementary children be able to use this name to find information that they can read and understand?” If you do a search using the name, do you find information that you can use and understand? If not, consider dropping the more technical name and using the common name for the lineage, the one I emphasize below. The terms on charts for children should be useful for understanding the diversity of life AND for finding further information.

Plant Kingdom (land plants, embryophytes)

Bryophytes (nonvascular plants)

                Liverworts (Phylum Marchantiophyta)

                Mosses (Phylum Bryophyta)

 Hornworts (Phylum Anthoceratophyta)

Vascular Plants or Tracheophytes

                Lycophytes or club mosses and relatives (Phylum Lycophyta)

                Euphyllophytes, the “true-leaf” plants

                       Fern clade or Monilophytes (Class Polypodiopsida)

                                  Whisk ferns and relatives

                                   Equisetums or horsetails

                                   Ferns or leptosporangiate ferns or true ferns

                       Seed plants or Spermatophytes

                                    Gymnosperms

                                                   Cycads (Phylum Cycadophyta)

                                                   Ginkgo (Phylum Ginkgophyta)

                                                   Gnetophytes (Phylum Gnetophyta)

       Conifers (Phylum Pinophyta)

                                     Angiosperms or flowering plants (Phylum Magnoliophyta)

                                                                Basal angiosperms

                                                                Magnoliids

                                                                Monocots

                                                                Eudicots

                                                               

For a beginner’s chart, I start the plant kingdom with the land plants, the embryophytes. It is acceptable to add the green algae because they are closely related to embryophytes, but it is clearer if children learn about land plants first, and then add their relatives. Advanced students are ready for a chart of the Viridiplantae (green plants), which includes the green algae lineages and the land plants. It is important for children to understand that land plants and green algae share a common ancestor.

Don’t feel bad about leaving off phylum/division names. While the animal kingdom phyla have been rearranged by DNA studies, they have kept their names. Plant kingdom phyla or divisions, whichever you wish to call them, aren’t as useful anymore. In fact, I have a widely-used, advanced textbook for plant systematics that uses no phylum/division names at all. Instead, it simply uses names with no ranks for the major lineages, such as lycophytes, euphyllophytes, seed plants, and angiosperms. It still uses orders, families, genera, and species, the Linnaean ranks that botanists continue to use for plants.  

There has been a big change that centers on the ferns. An older scheme had four phyla, Psilophyta, Lycophyta, Sphenophyta, and Pterophyta or Pteridophyta. These groups, often called “ferns and fern allies,” were considered more or less equal, but now we know that the lycophytes are a separate lineage from the other three. The fern clade, now considered by some to be a phylum, has three groups once considered separate phyla – the whisk ferns, horsetails, and the true ferns.

I see no reason to put notably out-of-date information on a plant kingdom chart. I especially encourage you to remove any images that are no longer considered plants. If you still have a mushroom on your plant kingdom chart, children are going to associate fungi with plants, even if you tell them that we know now that fungi are closely related to the animal kingdom and not at all close to plants. The visual impression that a chart gives to children is powerful, and it is important to get it as close to current as we can.

Change seems to come slowly in the general knowledge of plant systematics. I did an Internet search for plant kingdom charts and classification, and I found an amazing range of information from very old to current. Some websites even use the terms “cryptogams” and “phanerogams,” which came into use about 1860. Botanists haven’t used them in academic publications for at least 40 years. It is not that they are “wrong,” but they describe a superficial view that botanists had over a century ago. Our knowledge has grown, and there are better ways of expressing the differences among plant groups.

The flowering plants are currently divided into several lineages. I listed the main ones above, basal angiosperms, magnoliids, monocots, and eudicots. Botanists no longer use only the monocot and dicot subgroups, although these are still common in field guides and older publications. The flowering plants make up about 90% of the plant kingdom, and their orders have been defined in the last two or three decades using DNA studies. They deserve their own chart of orders and families.

My plant kingdom chart from my Tree of Life shows the lineages and their relationships. The plant kingdom chart from InPrint for Children gives children more practice with the categories.    

Here are some quick ways to check the information on a plant kingdom chart for your classroom. If the chart shows a row of evenly spaced boxes, it isn’t giving children all the information they need. Bryophytes need to be grouped together and somehow spaced apart from the tracheophytes. Lycophytes should be separated from other spore-producing plants. If the club mosses, whisk ferns, true ferns, and horsetails are all grouped together and perhaps called “fern allies” or “pteridophytes,” that’s obsolete. There should be something to show that the club mosses are a different lineage from the three branches of the fern clade, and if possible, that ferns are more closely related to seed plants. If the term “dicots” or “dicotyledons” appears instead of “eudicots,” then that needs to change. Eudicots (“true dicots”) are the old dicots minus the magnoliids and the basal lineages such as water lilies.

The same criteria for illustrations on a kingdom chart apply to animals and plants. Can you see the important structural features that enable children to recognize the lineage? For example, can you see a fern’s fiddleheads or its sori? Can you see the sporophytes of the bryophyte lineages? Sporophytes need to be visible and described in the text. The reproductive structures and foliage of the gymnosperms help children tell the difference between those lineages. Flower illustrations should clearly show stamens and pistils. Consider showing a fruit as well because fruits are unique to the flowering plants.

In the text for the chart, give children a range of examples whenever this is possible. Children, like much of our society, are less likely to be familiar with plants than they are with animals. They may be surprised to learn that grasses, maples, and oak trees are flowering plants.

Enjoy opening children’s eyes to the diversity of plants! For more information about the plant kingdom and its members, see my book, Kingdoms of Life Connected.


Help with studies of flowering plant families June 01 2017, 1 Comment

For many years, I have promoted the idea of structuring botany around the flowering plant families. It’s a practical way of addressing the diversity of the angiosperms, and it is knowledge that works in many places and at many levels. For instance, organic gardeners need to know the families of vegetables so that they can do the proper crop rotation and fertilizing. Plant identification is much easier if one can determine the family. Flowers in the same family share certain features, so it is quite possible to recognize the family even if you have never seen that species before.

To help you with your botany studies, I’ve just revised and expanded my PowerPoint slides on flowering plant families. This file is a pdf that can be printed to make letter-sized posters of 20 flowering plant families. The slides include text that describes the features of the flowers, and they show photos of family members. To round out this material, I’ve added a representative photo of 48 other families or subfamilies from all branches of the angiosperms. 

Perhaps you would like to do a Tree of Life diagram for the flowering plants. There is a good one in the book, Botanicum by Katie Scott and Kathy Willis. It is part of the Welcome to the Museum series from Big Picture Press (no relation to Big Picture Science), and it was published in 2016. The branches are correct on the diagram (pages 2 and 3), but they have just one example for each branch, and the orders are not stated. The example represents a whole order, which leaves out a lot. For example, the rose order, Rosales, is represented by a mulberry leaf. Mulberries and figs belong to family Moraceae, which is in the rose order, along with rose, elm, buckthorn, hemp, and nettle families. On the other hand, the diagram fits on two pages. It have to be much larger to be more comprehensive. All-in-all, the book is delightful and will provide lots of fun browsing. You will have to tell children that the page on fungi is a holdover from earlier definitions of botany.

The photos of families from my newly revised Flowering Plant Families Slides can be used to create a Tree of Life that has many orders. It gives a broader look at the families than its predecessor, and it is still centered on the families of North America. There are over 400 families of angiosperms worldwide. You don’t need to worry about being anywhere near comprehensive when you introduce children to flower families. Select the main ones for which you have examples from your school landscape, in areas near the school, or as cut flowers. If you or your children want to see the full list, go to the Wikipedia article on APG IV system (Angiosperm Phylogeny Group IV).   

I’m not the only one that advocates structuring botany studies around flowering plant families. Thomas Elpel has written a highly successful book called Botany in a Day: The Pattern Method of Plant Identification. It is further described as “An Herbal Field Guide to Plant Families of North America.”  This book is in its sixth edition. It has color drawings as well as black and white ones, and these could be useful in classrooms. I have not recommended placing this book in the elementary classroom, however, because it includes many food and medicinal uses for wild plants. I do not want to encourage children to eat wild plants or use them as medicine.

Botany in a Day is available from Mountain Press Publishing in Missoula, Montana, which also carries Elpel’s flower family book for children, Shanleya’s Quest. This book is a great one for elementary classrooms, and I strongly recommend it.

Enjoy exploring and identifying the flowers!


Plant surprises in the desert February 17 2017, 0 Comments

In January, I visited Tucson, Arizona and enjoyed exploring the Sonoran Desert. The plants there show many adaptations to the heat and dryness. The cacti and palo verde trees are what I expected. What surprised me is that plants I thought would need much more moisture are also able to survive in that climate.

There had been rain before my visit, enough that several hiking trails were impassable because normally dry creeks were flowing. As usual, if you want life, just add water. The plants that need moisture to reproduce, the spore-bearing plants, came out of hiding and were thriving. I saw a number of different ferns, but those weren’t a big surprise. I had seen ferns growing from cracks in lava flows before. The key for ferns seems to be finding a moisture-conserving crack on the shady side of a rock outcrop.

The spike mosses, genus Selaginella, were fluffed out and green. One of their common names is resurrection plant, so you can image how they look when they are dry. Spike mosses are not true mosses. They are members of the club moss lineage aka the lycophytes. One Sonoran species, Selaginella rupicola, is called rock-loving spike moss.  There were hillsides with many spike mosses protruding from cracks between rocks.

The mosses were looking very green and active. They are known for their ability to dry out and wait for water. They formed their green carpets out on more open ground and in sheltered rock overhangs. It was in one of the latter habitats that I found the big surprise. There were liverworts growing with the mosses.

Liverworts are the plants that have leaf pores that are always open. I think of liverworts as growing in habitats that have abundant moisture, not just isolated periods of wet weather. It is true that the liverworts in Oregon’s Willamette Valley survive the summer drought, but the humidity is never as low nor the temperatures as high as in the Sonoran Desert. The Sonoran liverworts are small, thalloid ones, much smaller than the ones native to western Oregon. They have the right appearance for a liverwort. They look like a flat leaf growing right on the ground, and they branch into two equal parts, which gives them a “Y” shape. They must have special adaptations and be very tough and resilient to live the desert.

Plants offer surprises in all habitats, not just the desert. You just have to take the time to look.