Someone has posted my Tree of Life chart on Pinterest and suggested in the caption that it could be a substitute for the Timeline of Life. NOT SO! These are two different materials with two different uses.
The Tree of Life does not show details of life through time. It shows extant animals and their lineages. People may be confused because classification has an element of time now. We group organisms by their common ancestors. You can’t show relatives without some reference to time. My cousins and I share a set of grandparents, so we have a recent common ancestor. That’s what makes us closely related.
Classification has become systematics (more on that in a later post). Biologists do not show rows of evenly spaced boxes with no connections when they diagram a kingdom or other related life. Instead, they connect the boxes (or names) with a branching diagram to show which organisms share more recent common ancestors.
The Tree of Life chart is used much like a Five Kingdoms chart was. If you are still using a Five Kingdoms, Six Kingdoms, or heaven forbid, a Two Kingdoms chart, you need to change to a different kind of chart. A Tree of Life chart is used to introduce children to the diversity of life. When I give this lesson, I tell children that this chart has a branch for all the major kinds of life on Earth. (And you may have one precocious child who asks “What about viruses?” No, they don’t belong on the organisms’ Tree of Life. They have their own.)
I can envision directing children’s attention to the big, black branches and noting that they are all connected, and they all share a common origin. I would also say that there are many, many varieties of life, and we would have a hard time studying it all at once. Instead, we put certain branches together for the purpose of focusing on them. Three of these major branches are called kingdoms because they are all the descendants of a common ancestor. They are outlined with color rectangles – yellow for fungi, red for animals, and green for land plants. The other two rectangles show organisms that we put together for the purposes of study – purple for prokaryotes and blue for protists.
The Tree of Life is used for children ages 6-9 to show them the big overview of life. They enjoy putting the cards on the solid, colored rectangles. The text on the back of the illustrations helps children place the picture of the organism. To help them find the right place, the major section and the name of the branch are in bold typeface. Older children and even secondary level students can still use the Tree of Life, and they should have an opportunity to place the cards and discuss this chart. Do they see that animals and fungi are sister kingdoms? This is why treating fungal infections is so hard.
On the other hand, the Timeline of Life shows the organisms that have lived during the time periods of the Phanerozoic Eon. A few timelines may have a bit of the previous Late Proterozoic, but the major emphasis is on life since the beginning of the Cambrian Period. There is nothing other than a timeline of life that can show this. Unfortunately the traditional Montessori Timeline of Life is riddled with mistakes – omission of the five major extinctions, all extinctions shown as ice ages, indistinct organisms, no grouping of related organisms, and my worst pet peeve, converging red lines that seem to show several lineages being fused into one.
OK, enough attacks on the Timeline of Life. It is still an important material for children, and I think it is important to use one that is updated and corrected, either by the teacher or by a company that has carefully researched its product. The Timeline of Life helps children understand how life has changed through time. (One last rant – add the Devonian explosion of plants! During that period, the land turned green as plants changed from a low green fuzz to trees that bore seeds. The Devonian – It’s not just for fishes!)
As a reminder of what is available on my website to aid you, my Outline of Geologic Time and the History of Life has lots of information that will help you make an accurate, up-to-date Timeline of Life. The Tree of Life chart is still a free download – my gift to the Montessori community. My book, Kingdoms of Life Connected, is a teacher’s guide to the tree of life. I updated it in the fall of 2016.
May you and your children enjoy exploring the living world, both its diversity and its history.
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.
Last June, the organization that officially recognizes the discovery of chemical elements and their names announced the proposed names for the final four elements on the periodic table. This governing body, the International Union of Pure and Applied Chemistry (IUPAC), took suggestions from the discoverers of the elements and then it issued the proposal. People could submit comments about the names for several months, and then in November, the IUPAC published the names. This was the final step in making them official.
The element names and atomic numbers are: nihonium (Nh) for element 113, which is named for the country of Japan; moscovium (Mc) for element 115, named for Moscow, Russia; tennessine (Ts) for element 117, named for the state of Tennessee; and oganesson (Og) for element 118, named after a Russian scientist who helped discover several elements, Yuri Oganessian. A new periodic table with these names is available at the IUPAC website, https://iupac.org/what-we-do/periodic-table-of-elements/ .
So what does this mean for the Montessori classroom? Children are ready for the abstract idea of chemical elements when they are in their elementary years. When they get an introduction to the periodic table, it should include the full set of names. Children should get a least a brief story of how elements get their names and how governing bodies of science fields bring order to science knowledge.
Children need to know, however, that there are elements that one cannot see with one’s eyes. There are quite a number of elements that are known only by the energy, particles, and atoms produced when they undergo radioactive decay.
The image below is from my newly updated card set, Discovering the Periodic Table. It comes with two sets of cards for all 118 elements, one in color and one in black and white. The card on the left is an example of the color set, and in this case sodium's symbol is color-coded red to show it is one of the alkali metals. The other card is the back of the black and white card, and it shows the type of information given for each element - physical properties, chemical properties, and other information. The front of the black and white card is like the card on the left, but with the symbol only outlined.
I updated and expanded Discovering the Periodic Table last summer after the new names were announced. At that time I added some features to help children understand the nature of the largest elements. The elements that cannot be made in visible quantities have symbols with a dotted outline rather than a solid one. The smallest of these is astatine, atomic number 85. Scientists have calculated that if one could make a piece of astatine, it would instantly vaporize itself because of the energy released by its vigorous radioactive decay.
If you tell children this, they may wonder how such an element was ever discovered. If they don’t think of it, help them arrive at this question. We want children to think about what they hear and ask about how we know what we know. The idea to search for astatine came from its place in the periodic table. Mendeleev left a blank beneath iodine on his first periodic table, implying that there was another element in the halogen family. Researchers that first identified this element used a nuclear reactor to bombard bismuth, atomic number 83, with alpha particles. This added two more protons to bismuth nuclei, and produced a small amount of astatine, which quickly decayed. Later, when researchers knew astatine’s characteristics, and they were able to find tiny traces of it in uranium ores.
After astatine, the next element that can’t be made in visible amounts is francium, atomic number 87. The dotted outline symbols don’t show up again until atomic number 101, mendelevium. It and all larger elements cannot be made in visible amounts. Researchers have made so little of elements 104-118 that the chemical properties of these elements are also unknown. In the cards with color-coded symbols from Discovering the Periodic Table, elements 104-118 have gray symbols to show that there is not enough evidence to assign them to a chemical group such the halogens.
Your children may ask if more elements can be discovered. In theory there could be, but if someone does discover more elements, it will be bigger science news than any recent element discovery. Meanwhile, help 6-9 year-olds explore the common everyday elements with the cards set, Elements Around Us from InPrint for Children. The set, Element Knowledge, will help 9-15 year-olds learn element names, symbols, and several significant groups. This set includes the first 111 elements. You can add the names and symbols of the other seven if your children are interested. They certainly won’t see those symbols in any chemical formulas.
The second edition of my book, Kingdoms of Life Connected: A Teacher’s Guide to the Tree of Life, is available now. I wrote the first edition in 2008, and it was already time for an update this year. New information keeps coming in all fields of science. This leads to gradually evolving ideas, but change has been exceptionally rapid in the field of systematics, the study of the diversity of life.
The flood of DNA information continues, and we must bear that in mind in our presentations. It would be better to state that the story you tell is based on the evidence scientists have gathered for now. In the future, there could be adjustments. This doesn’t mean that all the information about the Tree of Life will change. Instead there will be small alterations. The potential for change certainly doesn’t excuse the presentation of obsolete classifications as anything other than history.
One of the hardest tasks for my book revision was finding up-to-date children’s books about the diversity of life. I had to leave many older, but valuable, books on the resource lists. At least it is easier to find out-of-print books now than it was a decade ago. I also found that publishers have reprinted some valuable older books. They include Peter Loewer’s Pond Water Zoo: An Introduction to Microscopic Life. Jean Jenkins illustrated this book in black and white, and it has attractive, clear drawings of many protists, bacteria, and microscopic animals, along with text that upper elementary children can read. You will have to warn your children that the classification scheme presented, the Five Kingdoms, is obsolete, but the information about the groups of organisms is still quite good.
A forty-year-old book by Alvin and Virginia Silverstein, Metamorphosis: Nature’s Magical Transformations, has been reprinted by Dover Books. It has a chapter on sea squirts that shows the tadpole-like larval stage and tells about the life cycle of these chordates. I haven’t found another children’s book that tells this story. The black and white illustrations show how old the book is, but there didn’t seem to be a good alternative.
I know the pain of having to purchase a new edition of a reference book. My favorite biology textbook cost nearly $200, and I see the new edition, just published this month, is priced at $244. Yikes, that’s hard on the budget. If you own the first edition of Kingdoms of Life Connected, you will be able to purchase the ebook version – the pdf file – of the book at a reduced price. Please email info (at) bigpicturescience (dot) biz for information about how to do this.
I’m always happy to find children’s books that portray bacteria as something other than germs. In my recent searches, I’ve found three gems. Two of them came from Australia, but I found the shipping was quick. The publisher is Free Scale Network, and the books are sold by Small Friends Books http://www.smallfriendsbooks.com/. The authors are Ailsa Wild, Aviva Reed, Briony Barr, and Dr. Gregory Crocetti.
It’s not often that bacteria get to be the protagonists, but in The Squid, the Vibrio, and the Moon the heroes are bacteria that help a young bobtail squid evade its predators. The story is set near the Hawaiian Islands, and it is dramatic and engaging. The attractive illustrations do a great job of supporting the story. They combine scales and will need some explanation, but the size scale at the front will help children keep all the components of the story in perspective.
The second book, Zobi and the Zoox, is set in a coral colony on the Great Barrier Reef. The protagonist is a rhizobia bacterium, Zobi for short. The action takes place in a coral polyp named Darian. The personification of these organisms could be distracting, but it isn’t. It helps one keep the characters separate and follow the action. There’s plenty of action as the coral faces warming in the ocean.
Both of these books can give children a greater appreciation for the many roles that bacteria play in making the biosphere work. It is easy to say that bacteria are an important part of all ecosystems, but that statement needs to be followed with great examples of actual symbioses like these books provide.
These two books are 38 pages long, and they can be enjoyed as a read-aloud by beginning elementary children. Older elementary can read the books themselves, and even secondary levels can learn from them. There is a glossary and several pages of additional information in the back of the books.
The third book that would be a great addition for studies of the microbial world is Inside Your Insides: A Guide to the Microbes That Call You Home by Claire Eamer, illustrated by Marie-Eve Tremblay. It was just released this month. This book has a wide range of information about microbes – what they are, where they live, and what they have to do with us and our world. The illustrations are goofy and cartoonish, but they work well enough to help children picture what is going on. The information is accurate and current, something that is hard to find in any children’s science book, much less one on microbes. Upper elementary children will likely enjoy the corny jokes sprinkled through the book, but they will also find plenty of good information. You could read it to lower elementary children.
If you look closely at my Tree of Life chart, you may notice changes. Knowledge about the early branches of the eukaryotes has grown, and it was time for another adjustment in the protists. This time I changed the label on the unikonts to also include a newer term for them, the Amorphea. Some biologists wanted this change because the original hypothesis about what makes the unikonts unique failed. The unikonts do not always have one flagellum, and they have two basal bodies (the part from which flagella grow), like other eukaryotes. What they do have is a unique fusion of three genes. This condition is so rare that it is unlikely to arise twice. The lineage of amoebas, animals, and fungi is still called the unikonts by many biologists, so I left that name on the chart.
The other main branch of eukaryotes, known informally as the bikonts, has a fusion of two different genes, another rare feature. The branch that includes chromalveolates (brown algae, diatoms, ciliates, etc.) and rhizarians (foraminiferans, radiolarians, etc.) has a much less wieldy name. It is now known as SAR (or Sar), an abbreviation for stramenopiles, alveolates, and rhizarians, and I added this to the chart. The evidence now points to some associations that I wanted to include on my Tree of Life. It appears that the Archaeplastida and SAR are more closely related to each other than they are to the Excavata (euglenas, Giardia, etc.). I’ve moved the branch positions on the chart to show this.
I like a newer term for the main branches of the eukaryotes. They are called the eukaryotic supergroups, which is a good descriptor for them.
You may be wondering what to do with your Tree of Life chart if you printed it from the older files. At lower elementary, I would do little more than adding the SAR and Amorphea labels. At that level, it is about showing a broad sweep of life, not the more exacting details. At upper elementary, you may wish to briefly explain about the changes since your chart was printed. Secondary students can learn more about these changes and modify their chart if they are interested.
And then there is that little fact we like to ignore. There are at least as many organisms not shown on our charts (even the more sophisticated scientific ones) as we show there. DNA studies show as many or more bacteria that have never been cultured or named as known bacteria. There are many named, but unplaced protists. Life isn’t simple! Is this the last version of the Tree of Life? Not likely, but it works for now.
You may also be wondering why I bothered to change the chart. Why not start new users of it with the most up-to-date information? As the flood of information continues, it will be best to go forward, not back. The most important thing is that children understand the Tree of Life and the evolutionary history it reflects. As a recent article in Nature Microbiology (2016, article number 16048) states “The tree of life is one of the most important organizing principles in biology.”
Smile! It makes you feel good, and it helps others to do the same. I found some interesting ideas about how did our ability to have facial expressions arose as I researched mammals lately. It all started long ago with the first synapsids, the lineage that led to mammals. Although Dimetrodon is a synapsid on a different branch of life than mammals, that animal has a piece of the puzzle on smiles.
“Dimetrodon” means “two measure teeth” or “two long teeth.” Compared to its reptilian sister lineage, the synapsids were experimenting with different shapes, sizes, and therefore, functions of teeth. The reptiles, even the dinosaurs, have more uniform teeth. This shows two different strategies for eating and digestion. Synapsids developed the ability to chew their food. Reptiles, with only a few exceptions, are bulk feeders, meaning that they eat large pieces of food (like a snake eating a rat) and digest them slowly or they use a muscular stomach to grind the food (like birds and other dinosaurs).
The study of mammal evolution focuses a great deal on the study of teeth. Not only do teeth fossilize well, they show the changes as mammals arose and lineages developed. A key characteristic of mammals is teeth that can do a better job of biting, chewing, and grinding.
What’s the big deal about chewing our food? It has to do with how fast the food can be broken down by digestive enzymes. All the action of enzymes is at the surface of the food. Lots of surface area equals fast digestion. And why would one want to digest food quickly? Quick digestion leads to quick metabolism and production of molecules that supply energy to cells. It is necessary if the animal is warm-blooded and has a large brain. Maintaining our body temperature and feeding our brains are very expensive in calories.
OK, we chew our food and digest it quickly, maintain our warm body temperature, and feed our expensive brains. What does that have to do with smiling? In order to chew food, an animal needs muscles that operate the jaw. That seems straight forward enough. Those muscles must attach to the head, and an array of muscles around the head brings another possibility – the ability to have facial expressions.
Have you ever seen a facial expression on a fish, amphibian, reptile, or any of the avian dinosaurs, aka birds? They don’t chew their food, and they have few, if any, facial expressions.
Most mammals, on the other hand, have many facial expressions. Evolution is not a straight line, climb-the-ladder sort of thing, so some mammals have lost the ability to have facial expressions. Or perhaps their expressions are so subtle that we can’t see them. I’m thinking of whales and dolphins. Their use of sound to communicate probably works better than small visual changes because of their aquatic environment.
The social mammals that live on land have many ways to communicate. Many mammals use the position of their ears to express themselves. A snarl shows teeth and speaks loudly across many mammal lineages. Facial expressions are important and versatile ways of communicating for the more visual lineages, like primates. Our smiles likely started millions of years ago, judging by the use of facial expressions in our fellow great apes.
I recommend a generous bestowing of smiles on your fellow humans. You can celebrate that your ancestors took the road to chewing food as you smile. It is a fine thing to celebrate the wonder of our long journey as a species as well.
The first time I introduced children to the chemical elements, I wanted to give them a sense of where they might find these substances, either as single elements or in combination with others. Laying out the periodic table is one experience with the elements, but it is quite abstract and disconnected with everyday life. I wanted to help children learn about the elements in common substances, items they could encounter and experience.
I made a set of cards that had pictures of items, and I listed the major elements in each one on the back of the card. To let you know how long ago that was, I printed the lists of elements with a dot matrix printer and an Apple II computer. Fast forward a decade or so, and Carolyn Jones of InPrint for Children was designing a new series of materials for study of matter and atoms in Montessori elementary classrooms. We discussed the idea of a card set that shows common objects and their elements. She took the idea and produced an attractive set of cards that she calls “Elements Around Us.” Presently, only Big Picture Science sells this set.
“Elements Around Us” has photos of 20 objects. The set includes two copies of each card, one to leave whole with text that tells the elements, and one to cut apart for matching. We intentionally used some substances to simulate thinking. The photo of a cotton towel (which is mainly cellulose) and table sugar both say “This is composed of carbon, oxygen, and hydrogen.” Cellulose is a macromolecule that is built of sugar molecules. These cards lead to the concept that elements can be joined in many ways to make different substances. The card that shows gold colored coins lists no gold as an ingredient. There are cards for carbon in the form of graphite and of diamond.
After children have worked with the cards, they are often interested in doing more. The “Elements Around Us” set has a black line master called a replicard, which you can copy for children so they can make their own booklets. They can color the outline drawing and write the elements. There are two blanks for children to draw their own object and research its elements.
Elementary children who are past the stage for card materials or who want to pursue the idea further will likely enjoy How to Make a Universe with 92 Ingredients, a book by Adrian Dingle. The book, Planet in a Pebble, by Jan Zalasiewicz, begins with a chapter on the elements in a common beach pebble. This book is for adult general readers, but selections from it can be read to older children or read by secondary students.
Happy element hunting!
World Read Aloud Day, February 24th, slid by me while I wasn’t looking, but I hope you celebrate reading aloud every day. I learned about the “official” holiday from Science Books and Films (SB&F) February issue, which included this book list.
10 STEM Books for Reading Aloud
A Chicken Followed Me Home, by Robin Page. Simon & Schuster, 2015.
You Nest Here With Me, by Jane Yolen and Heidi Stemple. (Illus. by Melissa Sweet.) Boyds Mills Press, 2015.
Tiny Creatures: The World of Microbes, by Nicola Davies. (Illus by Emily Sutton.) Candlewick Press, 2014.
Raindrops Roll, by April Pulley Sayre. Beach Lane Books, 2015.
Winter Bees and Other Poems of the Cold, by Joyce Sidman. (Illus. by Rick Allen.) HMH Books for Young Readers, 2014.
One Plastic Bag: Isatou Ceesay and the Recycling Women of the Gambia, by Miranda Paul. (Illus. by Elizabeth Zunon.) Millbrook, 2015.
Tree of Wonder, by Kate Messner. (Illus. by Simona Mulazzani.) Chronicle Books, 2015.
High Tide for Horseshoe Crabs, by Lisa Kahn Schnell. (Illus. by Alan Marks.) Charlesbridge, 2015.
Waiting for Ice, by Sandra Markle (Illus. by Alan Marks.) Charlesbridge, 2012.
Feathers: Not Just for Flying, by Melissa Stewart. (Illus. by Sandra S. Brannan.) Charlesbridge, 2014.
I reviewed Tiny Creatures in a post for September 2014. Feathers: Not Just for Flying is a favorite of mine, both for the beautiful artwork and the science content.
If you subscribe to SB&F, you will receive the full content, which includes special features like this month’s list of books about technology and innovation for Black History Month. There is also a Read-Around-A-Theme feature on bats, and the usual great reviews of books for kindergarten through adult general readers.
If you can’t subscribe now, you can still get several valuable resources on the SB&F website (http://www.sbfonline.com/Pages/welcomesplash.aspx). This month there is a list of children’s books to celebrate spring, biographies of women in science, and science poetry for kids.
I have two new posters that do a good job showing the history and diversity of life. The first is just out from Fairhope Graphics, and it is called “A History of Existing Angiosperms.” The many branches of flowering plants show up very well on this poster. You can see why there’s more to flowering plant lineages than monocots and dicots. The timescale on the left of this poster could lead to confusion, so you will need to explain to your children that all the pictures show flowering plants that still exist. Each illustration is placed at the time when we think its lineage originated.
An important qualifier for this information – plant fossils are so much harder to find than large vertebrate fossils. Paleobotanists have to piece the story together from small, hard-to-preserve fragments, not large bones, so it could well be that a number of these plants will have a different age of origin as scientists obtain more fossil data. That should not detract from the information show here, however.
You can see from this poster that the plants had developed their major lineages before the K-Pg (K-T) extinction, and these lineages survived much better than the large vertebrates. The poster has the number of species and the common names of a few members for each lineage.
Look for the three main branches of angiosperms, the magnoliids, the monocots, and the eudicots, on the poster. You can also find two large branches of the eudicots, the rosids and the asterids. The rosids split into the fabids and the malvids. The asterid subdivisions are the lamiids and campanulids. These seem like a bunch of big meaningless names until you put a flower image with them, so this Fairhope Graphics poster will help make the lineages more memorable.
Fairhope Graphics also has useful posters on the lineages of birds, the Tree of Life at a simple and more advanced level, and the history of the Earth.
My second recently acquired poster is from a company called Evogeneao, which they explain on their website is short for evolutionary genealogy. The motto of this organization is “Life on Earth is one big extended family.” Their “Evolution Cousin” poster shows their branching diagram for all of life, along with several familiar organisms and a number that reflects their relationship to us. For instance, your cat is your 27 millionth cousin. You can also get a larger poster that features the Tree of Life as the main graphic and gives information about it. These posters would be great for an impressionistic lesson on the Tree of Life. If you decide to use one of these posters in your classroom (or even if you do not) you will find it useful to read the Tree of Life page under the “Learn” menu on the Evogeneao website.
Under the “Explore” menu there, you can select “Tree of Life Explorer.” When you can click on an organism, you will see lines appear from humans and the selected organism. These lines meet at the most recent common ancestor. It is a very cool illustration of our relation to all of life.