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Tweaking the Tree of Life December 14 2014, 2 Comments

 

I’ve made a few changes to my Tree of Life and have new files available for free download. The changes are in the prokaryotes and protists. The three true kingdoms, the plants, animals, and fungi are still the same. These changes aren’t large, but they make the chart more accurate and useful.

Perhaps I should start by stating current rules on what constitutes a kingdom. Like any other lineage of life, a kingdom is an ancestor and all of its descendants. Organisms that are not descendants of that ancestor are excluded. That is why the Five Kingdom classification is no longer used. Two of those kingdoms, Monera and Protista, are not valid.

On my prokaryote chart, the only change is in the title. I’ve changed “Kingdom Monera” to “formerly Kingdom Monera” and reduced the font size. I wanted put stronger emphasis on the fact that Kingdom Monera is obsolete. It is no longer accepted by biologists because the two branches, bacteria and archaea, are tremendously different at the cell level. While they may have shared an ancestor very long ago, that ancestor would be the ancestor of all life, not just prokaryotic life.

On my protist chart, I changed both the title and the rhizaria branch. Biologists have good evidence that the rhizaria lineage, the stramenopile lineage, and the alveolate lineage shared a common ancestor more recently than the common ancestor of eukaryotes. The lineage is called SAR, an abbreviation for stramenopile, alveolate, and rhizaria. On the chart, I moved the base of the rhizaria lineage up onto the chromalveolate branch (which symbolizes the common ancestors of stramenopiles and aveolates) rather than showing the rhizaria as equally related to all the bikonts.

There are many uncertainties still in the protists, which are not a kingdom because they exclude the plants, animals and fungi. For convenience biologists group these eukaryotes into the informal group we call protists. There is an overwhelming amount of variety in this hodge-podge of life. When you introduce children to the protists, it is good to tell them that the branches on the chart are just the main branches, the ones with many known members. There are lots of other smaller branches as well. New protists are still being discovered and many that we have known of for years are yet to be studied enough to place them on the Tree of Life.

The Tree of Life gives a good framework for children to use as they address further diversity of life. It’s good to remind them that each of the main branches on the chart holds many other lineages, and life is always surprising us with its endless experiments. No chart will be valid for decades, at least not until we have studied many more organisms and determined configurations of many more lineages.

Happy explorations in life. You can use the comments to ask questions about these changes.

Priscilla


New Product: the Animal Kingdom Chart from InPrint for Children November 07 2014, 0 Comments

Big Picture Science now sells the Animal Kingdom Chart from InPrint for Children. Our stock is the latest printing of this chart, so it has new features. Carolyn Jones Spearman, who is the owner and designer of InPrint for Children, is meticulous in her images and designs. Each time she reprints this chart, she consults me for the latest updates.

With the high rate of change in life science, fueled by new DNA information and Tree-of-Life paradigms, there has been something to change on each printing. On this one, the material is a laminated sheet that lies flat. The color scheme is refined, and there are two new labels placed near the bottom to show the animals that are on the protostome and deuterostome branches of life. These branches are shown on my Tree-of-Life diagram for the animal kingdom.

If you are not familiar with these branches, they are explained in my book, Kingdoms of Life Connected. Briefly, the protostome (“mouth first”) lineage includes mollusks, annelids, arthropods, and roundworms. The deuterostome (“mouth second”) lineage includes echinoderms and chordates. One interesting difference between these two lineages is that identical twins are only possible in the deuterostomes. Their fertilized eggs keep the ability to develop into many tissues through several cell divisions, whereas the protostome cells specialize early. The deuterostome embryos can be divided in half and go on to form two individuals. The protostome embryos die if they are divided in half.

InPrint for Children’s Animal Kingdom Chart includes color cards to place on the chart. Each one illustrates an animal and has information about it on the back. There is a subtle clue to the animal’s environment in the shading behind the animal’s image. If the shading is blue, the animal is aquatic. If it is green, the animal is terrestrial, and if it is pinkish, the animal is a parasite.

This animal kingdom chart provides further experience for children, after they have seen the place of the animal kingdom in the Tree of Life, and after they have an introduction to the major branches of the animal kingdom. Those introductions can be done with my Tree-of-Life charts. The advantage of the chart from InPrint for Children is that it gives children more practice and introduces them to more members of the lineages of animals. The grouping of phyla on the chart reflects the branches on the Tree of Life. For instance, the arthropods and the roundworms, members of the molting animal lineage (edysozoa) are placed side-by-side with a wider margin between them and other branches of animals.

The InPrint for Children chart clarifies the confusion between chordates and vertebrates. Some Montessori materials show non-chordates and chordates rather than invertebrates and vertebrates. Those two groupings are not the same. The tunicates and lancelets are invertebrate chordates. The line on the bottom of the chart shows which animals are vertebrates and which are not.

There is a lot to learn by working with this chart. I hope you and your children find it an inspiring entrance into study of the animals.


Picturing the Tree of Life August 16 2014, 0 Comments

I have just received two posters that depict the Tree of Life. They are from Fairhope Graphics - www.fairhopegraphics.com. One is a basic level illustration for younger children. Its title is "A Story of the Life Around Us," and it has reasonable simplifications for beginners. The Archaea aren't shown, for example. The artwork is bright and inviting, and best of all, the information that is shown looks quite accurate. This poster would be good for beginning lower elementary students, and perhaps even for kindergarten age children. You may have to explain to children that the leaves pictured around the tree represent extant organisms, and are more than just leaves. When children are ready for more details, the second poster, "A History of Existing Life," supplies more of the story and does it attractively and with good accuracy. The Archaea are here, as well as major branches of both prokaryotic domains. Red lines show the endosymbiosis of mitochondria and chloroplasts. The chloroplast line could have been better placed to point to the archaeplastida, but at least it comes from the right branch, the cyanobacteria. The protists get more space on this poster, and the major branches of the eukaryotes are shown. There's an approximate timescale on the left, with arching lines across the tree that show the five major extinctions. I like seeing names such as eudicot, Deuterostomia; Ecdysozoa; and Amniota. The birds are shown properly as a branch of the reptiles, specifically the dinosaur branch of the archosaurs. The organisms pictured on the poster are extant, and they are illustrated with attractive 19th century artwork. These authors did their homework and produced a useful learning aid for all of us. The caption on the tag says that the posters grew out of a "family's journey to understand the connections between fossils they had found and the sea urchins they loved in Maine tidal pools." What a great product of curiosity!

It is important for children to see these "cartoon" tree-of-life diagrams before they see the official scientific evolutionary trees. It is much easier to mentally picture the branches and keep them straight with the simplified diagrams. That is the approach I took with my Tree-of-Life chart. You can find my diagram with my products, and download it for free.