Children’s Books About Evolution

Evolution is a difficult subject to learn, let alone teach. Because evolution is generally such a slow process, it involves a timeline that is challenging for us to comprehend. Evolution is also commonly misunderstood, so misconceptions abound, be they purposeful misrepresentations, gaps in understanding, or otherwise. Wrapping one’s brain around even the basic tenets of evolution can take years of study, yet it is one of the most fundamental concepts of biology; failing to understand it stifles one’s knowledge of and appreciation for the study of life on Earth. On the flipside, gaining an understanding of the workings of evolution can inspire a greater appreciation for our place in the universe and can instill in oneself the urgency of conservation.

Despite being a tough subject to grasp, there is no reason why children should be exempt from learning about it. However, because it is such a complex topic, adults can struggle to find ways to explain it. Luckily, there are some great children’s books about evolution that introduce the subject in basic ways. These books are good starting points and can help cultivate a desire to explore the topic further. Understanding evolution and the science surrounding our world and the broader universe is a lifelong pursuit. Children will benefit from a head start.

What follows are reviews of a handful of books that may be useful in teaching kids about the theory of evolution.

I Used to Be a Fish by Tom Sullivan

i-used-to-be-a-fish

This book is an excellent place to start. It is a quick and easy read, and it introduces – in a very simple way – the evolutionary lineage of humans. It doubles as a lesson on evolution and, as Sullivan puts it, “a tribute to every child’s power to transform their lives and to dream big,” which is achieved by highlighting the imagination of the main character and defining evolution as the gradual development over a lifetime towards achieving goals and aspirations.

In the Author’s Note, Sullivan briefly explains some important aspects of evolution: it is “a very slow process” that “occurs over generations to entire populations of creatures,” it doesn’t occur in a straight line like the book implies but instead looks “more like a tree with many complicated branches,” and “it doesn’t happen because a creature wants it to.”

One step in our evolutionary lineage as depicted in I Used to Be a Fish by Tom Sullivan

One step in our evolutionary lineage as depicted in I Used to Be a Fish by Tom Sullivan

Life history

Timeline from I Used to Be a Fish by Tom Sullivan. Look how far we’ve come!

Grandmother Fish by Jonathan Tweet; illustrated by Karen Lewis

grandmother-fish

This book is similar to Sullivan’s book, but it adds a little more detail to the story and invites interaction from its audience. As major periods in our evolutionary lineage are reached, readers are asked to “wiggle” like our Grandmother Fish, “crawl” like our Grandmother Reptile, “squeak” like our Grandmother Mammal, “hoot” like our Grandmother Ape, and so on. As the story transitions from one main character to another, simplified versions of evolutionary trees are shown (like the one below).

grandmother-fish-2

A larger version of “Our Evolutionary Family Tree” is featured at the end of the story followed by several pages of additional information that adults can use to further explain evolution to children, including discussions on three major concepts of evolution (descent with modification, artificial selection, and natural selection), more details on the main characters in the book, and a guide to correcting common errors about evolution.

grandmother-fish-3

When Fish Got Feet, Sharks Got Teeth, and Bugs Began to Swarm by Hannah Bonner

when-fish-got-feet

This book is much more text heavy than the first two, but is still very approachable. The illustrations are both humorous and informative, and Bonner excels at explaining complex topics in a way that makes them easy to digest. Rather than covering hundreds of millions of years of evolution like the first two books, this book focuses mainly on events that occurred during the Silurian and Devonian periods – between 360 and 444 million years ago. It was during this time that plants were making their way to land and diverging into many different forms. Arthropods were doing the same. During this period, the earth’s atmosphere became more oxygen rich and soil began to accumulate largely due to the growth and expansion of land plants.

Recipe for a land plant from When Fish Got Feet by Hannah Bonner

Recipe for a land plant from When Fish Got Feet by Hannah Bonner

This was also a period of great diversification in the fish world. Jaws were becoming more common and skeletons made of bone (as opposed to cartilage) were developing.  The first tetrapods (fish with legs) emerged from the oceans and onto land in the Devonian period. These tetrapods were our early ancestors, and Bonner explains how some of the skeletal features that fish developed during this time period were precursors to our current skeleton.

Unlike the first two books, the evolution of plants receives some attention in Bonner’s book. It is during the Devonian period that the first trees and seed-bearing plants appear. As in the other books, there are additional resources at the end, including this important warning by Bonner: “Please remember that anyone can set up a Web site, so not everything you will encounter will be good science.”

A time line of life on earth from When Fish Got Feet by Hannah Bonner

A timeline of life on earth from When Fish Got Feet by Hannah Bonner

Key to helping children understand evolution is understanding it ourselves, and there are, of course, endless resources out there to help with this. I will suggest just two additional books. In keeping with the spirit of children’s books, there is a great illustrated biography of Charles Darwin (who is considered the Father of Evolution) called Darwin For Beginners by Jonathan Miller and Borin Van Loon. It’s basically Darwin’s life told in graphic novel form. And keeping with the fish theme, you can’t go wrong with Neil Shubin’s, Your Inner Fish, a fascinating look into the origins of many of the parts, pieces, and other features of the human body.

Do you have a favorite book, children’s or otherwise, about evolution? Please share it in the comment section below.

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What Is a Plant, and Why Should I Care? part four

What Is a Plant?

Part one and two of this series have hopefully answered that.

Why should you care?

Part three offered a pretty convincing answer: “if it wasn’t for [plants], there wouldn’t be much life on this planet to speak of.”

Plants are at the bottom of the food chain and are a principle component of most habitats. They play major roles in nutrient cycling, soil formation, the water cycle, air and water quality, and climate and weather patterns. The examples used in part three of this series to explain the diverse ways that plants provide habitat and food for other organisms apply to humans as well. However, humans have found numerous other uses for plants that are mostly unique to our species – some of which will be discussed here.

But first, some additional thoughts on photosynthesis. Plants photosynthesize thanks to the work accomplished by very early photoautotrophic bacteria that were confined to aquatic environments. These bacteria developed the metabolic processes and cellular components that were later co-opted (via symbiogensis) by early plants. Plants later colonized land, bringing with them the phenomena of photosynthesis and transforming life on earth as we know it. Single-celled organisms started this whole thing, and they continue to rule. That’s just something to keep in mind, since our focus tends to be on large, multi-cellular beings, overlooking all the tiny, less visible beings at work all around us making life possible.

Current representation of the tree of life. Microorganisms clearly dominate. (image credit: nature microbiology)

Current representation of the tree of life. Microorganisms clearly dominate. (image credit: nature microbiology)

Food is likely the first thing that comes to mind when considering what use plants are to humans. The domestication of plants and the development of agriculture are easily among the most important events in human history. Agricultural innovations continue today and are necessary in order to both feed a growing population and reduce our environmental impact. This is why efforts to discover and conserve crop wild relatives are so essential.

Plants don’t just feed us though. They house us, clothe us, medicate us, transport us, supply us, teach us, inspire us, and entertain us. Enumerating the untold ways that plants factor in to our daily lives is a monumental task. Rather than tackling that task here, I’ll suggest a few starting points: this Wikipedia page, this BGCI article, this Encylopedia of Life article, and this book by Anna Lewington. Learning about the countless uses humans have found for plants over millennia should inspire admiration for these green organisms. If that admiration leads to conservation, all the better. After all, if the plants go, so do we.

Humans have a long tradition of using plants as medicine. Despite all that we have discovered regarding the medicinal properties of plants, there remains much to be discovered. This one of the many reasons why plant conservation is so important. (photo credit: wikimedia commons)

Humans have a long tradition of using plants as medicine. Despite all that we have discovered regarding the medicinal properties of plants, there remains much to be discovered. This is one of the many reasons why plant conservation is imperative. (photo credit: wikimedia commons)

Gaining an appreciation for the things that plants do for us is increasingly important as our species becomes more urban. Our dense populations tend to push plants and other organisms out, yet we still rely on their “services” for survival. Many of the functions that plants serve out in the wild can be beneficial when incorporated into urban environments. Plants improve air quality, reduce noise pollution, mitigate urban heat islands, help manage storm water runoff, create habitat for urban wildlife, act as a windbreak, reduce soil erosion, and help save energy spent on cooling and heating. Taking advantage of these “ecosystem services” can help our cities become more liveable and sustainable. As the environmental, social, and economic benefits of “urban greening” are better understood, groups like San Francisco’s Friends of the Urban Forest are convening to help cities across the world go green.

The importance of plants as food, medicine, fuel, fiber, housing, habitat, and other resources is clear. Less obvious is the importance of plants in our psychological well being. Numerous studies have demonstrated that simply having plants nearby can offer benefits to one’s mental and physical health. Yet, urbanization and advancements in technology have resulted in humans spending more and more time indoors and living largely sedentary lives. Because of this shift, author Richard Louv and others warn about nature deficit disorder, a term not recognized as an actual condition by the medical community but meant to describe our disconnect with the natural world. A recent article in BBC News adds “nature knowledge deficit” to these warnings – collectively our knowledge about nature is slipping away because we don’t spend enough time in it.

The mounting evidence for the benefits of having nature nearby should be enough for us to want to protect it. However, recognizing that we are a part of that nature rather than apart from it should also be emphasized. The process that plants went through over hundreds of millions of years to move from water to land and then to become what they are today is parallel with the process that we went through. At no point in time did we become separate from this process. We are as natural as the plants. We may need them a bit more than they need us, but we are all part of a bigger picture. Perhaps coming to grips with this reality can help us develop greater compassion for ourselves as well as for the living world around us.

What Is a Plant, and Why Should I Care? part three

“If it wasn’t for the plants, and if it wasn’t for the invertebrates, our ancestors’ invasion of land could never have happened. There would have been no food on land. There would have been no ecosystems for them to populate. So really the whole ecosystem that Tiktaalik and its cousins were moving into back in the Devonian was a new ecosystem. … This didn’t exist a hundred million years before – shallow fresh water streams with soils that are stabilized by roots. Why? Because it took plants to do that – to make the [habitats] in the first place. So really plants, and the invertebrates that followed them, made the habitats that allowed our distant relatives to make the transition from life on water to life on land.” – Neil Shubin, author of Your Inner Fish, in an interview with Cara Santa Maria on episode 107 of her podcast, Talk Nerdy To Me

Plants were not the first living beings to colonize land – microorganisms have been terrestrial for what could be as long as 3.5 billion years, and lichens first formed on rocks somewhere between 550 and 635 million years ago – however, following in the footsteps of these other organisms, land plants paved the way for all other forms of terrestrial life as they migrated out of the waters and onto dry land.

The botanical invasion of land was a few billion years in the making and is worth a post of its own. What’s important to note at this point, is that the world was a much different place back then. For one, there was very little free oxygen. Today’s atmosphere is 21% oxygen; the first land plants emerged around 470 million years ago to an atmosphere that was composed of a mere 4% oxygen. Comparatively, the atmosphere back then was very carbon rich. Early plants radiated into numerous forms and spread across the land and, through processes like photosynthesis and carbon sequestration, helped to dramatically increase oxygen levels. A recent study found that early bryophytes played a major role in this process. The authors of this study state, “the progressive oxygenation of the Earth’s atmosphere was pivotal to the evolution of life.”

A recreation of a Cooksonia species - one of many early land plants. (photo credit: wikimedia commons)

A recreation of a Cooksonia species – one of many early land plants (photo credit: wikimedia commons)

The first land plants looked very different compared to the plants we are used to seeing today. Over the next few hundred million years plants developed new features as they adapted to life on land and to ever-changing conditions. Roots provided stability and access to water and nutrients. Vascular tissues helped transport water and nutrients to various plant parts. Woody stems helped plants reach new heights. Seeds offered an alternative means of preserving and disseminating progeny. Flowers – by partnering with animal life – provided a means of producing seeds without having to rely on wind, water, or gravity. And that’s just scratching the surface. Rooted in place and barely moving, if at all, plants appear inanimate and inactive, but it turns out they have a lot going on.

But what is a plant again? In part one and two, we listed three major features all plants have in common – multicellularity, cell walls composed of cellulose, and the ability to photosynthesize – and we discussed how being an autotroph (self-feeder/producer) sets plants apart from heterotrophs (consumers). Joseph Armstrong writes in his book, How the Earth Turned Green, “photosynthetic producers occupy the bottom rung of communities.” In other words, “all modern ecosystems rely upon autotrophic producers to capture energy and form the first step of a food chain because heterotrophs require pre-made organic molecules for energy and raw materials.”

So, why should we care about plants? Because if it wasn’t for them, there wouldn’t be much life on this planet to speak of, including ourselves.

Plants don’t just provide food though. They provide habitat as well. Plus they play major roles in the cycling of many different “nutrients,” including nitrogen, phosphorous, carbon, sulfur, etc. They are also a major feature in the water cycle. It is nearly impossible to list the countless, specific ways in which plants help support life on this planet, and so I offer two examples: moss and dead trees.

The diminutive stature of mosses may give one the impression that they are inconsequential and of little use. Not so. In her book, Gathering Moss, Robin Wall Kimmerer describes how mosses support diverse life forms:

There is a positive feedback loop created between mosses and humidity. The more mosses there are, the greater the humidity. More humidity leads inexorably to more mosses. The continual exhalation of mosses gives the temperate rain forest much of its essential character, from bird song to banana slugs. … Without mosses, there would be fewer insects and stepwise up the food chain, a deficit of thrushes.

Mosses are home to numerous invertebrate species. For many insects, mosses are a place to deposit their eggs and, consequentially, a place for their larvae to mature into adults. Banana slugs traverse the moss feeding on “the many inhabitants of a moss turf, and on the moss itself.” In the process they help to disperse the moss.

Moss is used as a nesting material by various species of birds, as well as squirrels, chipmunks, voles, bears, and other animals. Patches of moss can also function as “nurseries for infant trees.” In some instances, mosses inhibit seed germination, but they can also help protect seeds from drying out or being eaten. Kimmerer writes, “a seed falling on a bed of moss finds itself safely nestled among leafy shoots which can hold water longer than the bare soil and give it a head start on life.”

moss as nurse plant

Virtually all plants, from the tiniest tufts of grass to the tallest, towering trees have similar stories to tell about their interactions with other living things. Some have many more interactions than others, but all are “used” in some way. And even after they die, plants continue to interact with other organisms, as is the case with standing dead trees (a.k.a. snags).

In his book, Welcome to Subirdia, John Marzluff explains that when “hole creators” use dead and dying trees, they benefit a host of “hole users:”

Woodpeckers are natural engineers whose abandoned nest and roost cavities facilitate a great diversity of life, including birds, mammals, invertebrates, and many fungi, moss, and lichens. Without woodpeckers, birds such as chickadees and tits, swallows and martins, bluebirds, some flycatchers, nuthatches, wood ducks, hooded mergansers, and small owls would be homeless.

As plants die, they continue to provide food and habitat to a variety of other organisms. Eventually they are broken down to their most rudimentary components, and their nutrients are taken up and used by “new life.” Marzluff elaborates on this process:

Much of the ecological web exists out of sight – underground and in rotting wood. There, molds, bacteria, fungi, and a world of invertebrates convert the last molecules of sun-derived plant sugar to new life. These organisms are technically ‘decomposers,’ but functionally they are among the greatest of creators. Their bodies and chemical waste products provide us with an essential ecological service: soil, the foundation of terrestrial life.

Around 470 million years ago, plants found their way to land. Since then life of all kinds have made land their home. Plants helped lead the way. Today, plants continue their long tradition of supporting the living, both in life and in death.

Thoughts on Equisetum Phylogenesis

This a guest post. Words and photos by Jeremiah Sandler.

These notes do not discuss either anatomy or medicinal uses of Equisetum. Both topics are worthy of their own discourse.

Plants in the genus Equisetum can be found on each continent of our planet, except for Antarctica. The plants are collectively referred to as scouring rush or horsetail.  Equisetum is in the division of plants called Pteridophytes, which contains all of the ferns and fern-allies (lycopods, whisk ferns, etc.) Pteridophytes are characterized by having a vascular system and by reproducing with spores, rather than seeds. Equisetum is the only living genus within the entire class Equisetopsida.  Within this single genus, there are a mere 20 species.

Picture 1

Equisetums can live pretty much anywhere. They can tolerate lots of shade, lots of sun, and virtually any soil condition (including submerged soil). Rhizomatous stems make it difficult for either disease or insects to kill an entire population. They do not require pollinators because they reproduce with spores.  Sounds like a recipe for reproductive and evolutionary success. Yet with all of these traits working in their favor, there is only a single genus left.  

Where’d they all go?

Picture 2

Let’s briefly consider the origin of these plants first. In the late Paleozoic Era, during the end of the Cambrian Period, these plants began their takeover. Shortly thereafter (about 70 million years later), in the Devonian Period, land plants began to develop a tree-like habit, also called “arborescence.” Tree-sized ferns and fern-allies ruled the planet. They formed the ancient forests.

The elements required for photosynthesis were plentiful. The planet was warm. Competition from the Cambrian Explosion of flora and fauna drove plants upwards towards the sky. Larger plants can both shade their competition and remain out of reach of herbivores. None of the Equisetum species alive today are near their ancestors’ height.  

picture 3

It is rather obvious why we don’t see as many Equisetum species, and why they are not as large: The planet now is not the same planet it once was. Oxygen levels back in those times were about 15% higher than today’s levels. Seed plants can diversify much faster than non-seed-bearing plants; Equisetum cannot compete with the rate of diversification of seed-bearing plants.

The most interesting predicament comes when Equisetum is compared with other Pteridophytes. Some ancient Pteridophytes still do have diversity of genera. True Ferns, as they’re called, are broad-leaved ferns. In the class Filicopsida, there are 4 orders of True Ferns containing about 100 genera combined. Equisetum has 1 order and 1 genera.

What’s the primary difference between these two classes of Pteridophytes?  Broad leaves.

Most pteridophytes tolerate some shade; most other plants can’t tolerate as deep of shade as ferns. More specifically, the amount of shade the plants create could be a deciding factor in this question. True ferns have all of the traits equisetums have, with one additional physical trait that has pulled them ahead: Broad leaves allow true ferns to actively shade out local competition while creating more habitat for themselves. Equisetums don’t have this aggressive capacity.

Of course there are other biological and evolutionary pressures affecting equisetums beside their lack of broad leaves. The structure they do possess has benefited them at a time when it was advantageous to have it.  Otherwise why would it exist? Equisetums remind me of the dynamic nature of a planet. I don’t anticipate equisetums coming back. 

Although, I find it entertaining to humor the idea that they might return to their former glory. The planet’s climate could change toward any direction (I’m not a climatologist, though). Maybe equisetums are adequately prepared to adapt to whatever changes come – or maybe we are observing the gradual decline of an old branch on the tree of life.  

Resources:

What Is a Plant, and Why Should I Care? part two

“Organisms green with chlorophyll appeared pretty early in Earth history, diversified, and adapted to oceanic, coastal, and finally terrestrial environments. As this took place, the Earth turned green.” – Joseph E. Armstrong, How the Earth Turned Green

world turned green

The Earth not only turned green, but the composition of its atmosphere dramatically shifted. Thanks in part to photosynthesis, Earth’s atmosphere went from having virtually no free oxygen to being composed of about 21% oxygen. The increasing availability of oxygen helped facilitate the evolution of more and more diverse forms of life. Had photosynthesis (specifically oxygen-producing photosynthesis) never come about, the Earth would not be anything like it is today.

There are organisms in at least three taxonomic kingdoms that have the ability to photosynthesize: Bacteria, Protista, and Plantae. A book itself could be written about how photosynthesis developed and how it differs among organisms. The important thing to note in a discussion about plants is that the type of photosynthesis that occurs in cyanobacteria is the same type that occurs in the chloroplasts of plants and green algae. Additionally, pigments called chlorophyll are only found in cyanobacteria and the chloroplasts of plants and green algae. As Joseph Armstrong puts it in How the Earth Turned Green, “evidence strongly supports the hypothesis that chloroplasts were free-living photosynthetic bacteria that became cellular slaves within a host cell.”

In Part One, we established that green algae are closely related to plants, and that a subset of green algae colonized the land and evolved into modern day plants. Plants are green because of cyanobacteria via green algae; however, cyanobacteria are not plants, and green algae may or may not be plants depending on your preference. Classification is not nearly as important as determining evolutionary relationships.

So, again, what is a plant? K. J. Willis and J. C. McElwain offer this summary in their book, The Evolution of Plants: “Plants are relatively simple organisms with a common list of basic needs (water, carbon dioxide, nitrogen, magnesium, phosphorous, potassium, some trace elements, plus various biochemical pathways necessary for photosynthesis). This list has remained almost unchanged from the first land plants to the present.” In Part One, we also listed three major features that all plants have in common: multicellularity, cell walls that contain cellulose, and the ability to photosynthesize.

Photosynthesis is a big one, because it means that plants make their own food. They are autotrophs/self-feeders/ producers. This sets them apart from heterotrophs, organisms that consume other organisms in order to obtain energy and other essential nutrients. Plants are at the bottom of the food chain, providing energy and nutrients to all other organisms that either directly or indirectly consume them. In Armstrong’s words:

“Eating and being eaten is a fact of life, a process by which the light energy captured by green organisms is passed through a series of consumers, a food chain, before eventually being lost as heat, which dissipates. Everything else is recycled with the able assistance of decomposers, primarily fungi and microorganisms, heterotrophs who obtain their food from dead organisms or their metabolic wastes. A large part of ecology concerns such trophic or feeding interactions, the energy transfers that result, and the cycling of biogeochemicals, the elements of life.”

Their ability to photosynthesize, among other things, gives plants a prominent role in the world’s ecosystems. Much more will be said about that as we continue, but first there are a few other things about plants worth mentioning.

Plants exhibit modular growth. While animals generally produce all of their body parts early on in life and rarely reproduce new body parts in replacement of lost ones, plants can continue to reproduce and replace body parts. Even at maturity, plants maintain embryonic tissues, which allows them to regenerate body parts as needed. This is one reason why so many plants can be propagated asexually via stem, root, and/or leaf cuttings. Roots can be encouraged to grow from unlikely places, and a whole new plant can be produced as a result.

Plants are generally stationary. Rooted in place, they must obtain everything necessary for life, growth, and reproduction by accessing whatever resources are in their immediate vicinity. Roots search the soil for water and other nutrients, and leaves harvest sunlight and carbon dioxide to make sugars. Relationships are maintained with soil fungi to aid in the search for water and nutrients, but otherwise, plants are largely on their own. Since they cannot run or hide, they must stand and fend for themselves when insects and other herbivores come to devour them. They have adapted a variety of chemical and physical defenses to address this.

Despite being largely immobile during their juvenile and adult phases, plants can actually be incredibly mobile during their embryonic stage (or in other words, as seeds/spores/progules). Employing biotic and abiotic resources, seeds and spores can potentially move miles away from their parent plants, enjoying a freedom of movement they will never know again once they put their roots down.

It is estimated that the total number of plant species on the earth today is around 400,000. (For reference, see this BGCI page and this Kew Gardens page. See The Plant List for up to date plant species names.) The first land plants evolved around 450 million years ago. It wasn’t until around 160 million years ago that the first flowering plants appeared, yet about 90% of the plants in existence today fall within this group. How many tens of thousands of species of plants have existed on Earth throughout history? I don’t think we can say. So many have come and gone, while others have radiated into new species. Exploring life that currently exists on this planet is an enormous pursuit on its own; add to that the exploration of life that once existed, and your pursuits become endless.

Sticky purple geranium (Geranium viscosissimum) one species of around species of extant flowering plants.

Sticky purple geranium (Geranium viscosissimum) is just one of more than 350,000 species of extant flowering plants.

At the close of the first chapter of his book, Armstrong highlights eight major historical events that have brought us plants as we know them today: “the origin of life itself, the development of chlorophyll and photosynthesis, the advent of the eukaryotic (nucleated) cell, the development of multicellular organisms, the invasion of land, the development of vascular tissues, the development of seeds, and the development of flowers.”  Consider that a brief synopsis of all we have to cover as we continue to tell the story of plants.

What Is a Plant, and Why Should I Care? part one

I want to tell the story of plants. In order to do that, I suppose I will need to research the 4 billion year history of life on earth. And so I am. Apart from satiating my own curiosity, studying and telling the story of plants advances me towards my goal of creating a series of botany lesson themed posts. Botany 101 and beyond, if you will. An ambitious project, perhaps, but what else am I going to do with my time?

So what is a plant anyway? We all know plants when we see them, but have you ever tried to define them? They are living beings, but they are not animals. They are stationary – rooted in the ground, usually. Most of them are green, but not all of them. They photosynthesize, which means they use water, carbon dioxide collected from the atmosphere, and energy harvested from the sun to make food for themselves. No animal can do that (okay…a few sort of can). They reproduce sexually, but many can also reproduce asexually. They are incredibly diverse. Some grow hundreds of feet into the air. Some barely reach more than a few centimeters off the ground at maturity. They have discernible parts and pieces, but they can also lose parts and pieces and then grow them back. There aren’t many animals that can do that. They have been on this planet for hundreds of millions of years, colonizing land millions of years before animals. Plants helped pave the way, and if it weren’t for plants, animals may not have stood a chance.

I don’t mean to pick on animals, it’s just that for a long time, humans grouped living things into just two kingdoms: Plantae and Animalia. Stationary things that appeared to be rooted to the ground or some other surface were classified as plants. Green things that lived in the water were also considered plants. Thus, lichens, fungi, algae, and everything we consider to be a plant today were placed in kingdom Plantae. Everything else was placed in kingdom Animalia. This, of course, was before much was known about microorganisms.

Dichotomous classification was reconsidered as we learned more about the diversity of organisms in each kingdom, particularly as the theory of evolution came into play and microscopes allowed us to observe single celled organisms and chromosomes. Eventually, fungi was awarded its own kingdom, which includes lichens – organisms composed of both fungi and photosynthetic species but classified according to their fungal components. Most of the algae was placed in a kingdom called Protista, a hodgepodge group of unicellular and unicellular-colonial organisms, some of which are animal-like and some of which are plant-like. Two kingdoms were also formed for prokaryotic organisms (organisms with cells that lack membrane bound organelles): Bacteria and Archaea.

Illustration of one current itteration of kingdom classification system (illustration credit: wikimedia commons)

Taxonomic kingdoms as we currently consider them (illustration credit: wikimedia commons)

In short, the answer to what is a plant seems to be whatever organisms humans decide to put in kingdom Plantae. One problem with this answer is that some chose to include certain species of algae and others don’t. But why is that? It has to do with how plants evolved and became photosynthetic in the first place.

Microorganisms developed the ability to photosynthesize around 3.5 billion years ago; however, the photosynthetic process that plants use today appeared much later – around 2.7 billion years ago. It evolved in an organism called cyanobacteria – a prokaryote. Eukaryotic organisms were formed when one single cell organism was taken inside another single cell organism, a process known as symbiogenesis. In this case, cyanobacteria was taken up and the eukaryotic organisms known today as algae were formed. The incorporated cyanobacteria became known as chloroplasts.

Not all algae species went on to evolve into plants. A group known as green algae appears to be the most closely related to plants, and a certain subset of green algae colonized the land and evolved into modern day plants (also known as land plants). That is why some taxonomists choose to include green algae in the plant kingdom, excluding all other types of algae.

Common stonewort (Chara vulgaris, a species of green algae (photo credit: www.eol.org)

Common stonewort, Chara vulgaris, a species of green algae (photo credit: www.eol.org)

The term land plants refers to liverworts, hornworts, mosses, ferns, fern allies, gymnosperms, and flowering plants – or in other words, all vascular and non-vascular plants. Another all encompassing term for this large group of organisms is embryophytes (embryo-producing plants).

Still confused about what a plant is? Three main features can be attributed to all plants: 1. They are multicellular organisms. 2. Their cell structure includes a cell wall composed of cellulose 3. They are capable of photosynthesis. Many species of green algae are unicellular, which is an argument for leaving them out of kingdom Plantae. Certain parasitic plants like toothwort, dodder, and beech drops have lost all or most of their chlorophyll and no longer photosynthesize, but they are still plants.

Deciding what is and isn’t a plant ultimately comes down to evolutionary history and common ancestry. As Joseph Armstrong writes in his book, How the Earth Turned Green, “Our classifications of human artifacts are totally arbitrary, but to be useful scientifically our classification of life must accurately reflect groupings that resulted from real historical events, common ancestries.”

Obviously this is going to be a multi-part series, so I will have much more to tell you about plants in part two, etc. For now, this You Tube video offers a decent summary.

Biodiversity Dips When Japanese Rice Paddies Go Fallow

Large-scale farms that generally grow a single crop at a time and are managed conventionally are, by design, lacking in biodiversity. Abandoning such farms and allowing nature to take its course should, not surprisingly, result in a dramatic uptick in biodiversity. Plant colonization of abandoned farmland (also referred to as old field succession) is well studied and is regularly used as an example of secondary succession in ecology textbooks. The scenario seems obvious: cease agriculture operations, relinquish the land back to nature, and given enough time it will be transformed into a thriving natural community replete with diverse forms of plants and animals. This is an oversimplification, of course, and results will vary with each abandoned piece of land depending on the circumstances, but it generally seems to be the story. So what about when it isn’t?

Rice farming in Japan began at least 2400 years ago. Rice had been domesticated in China long before that, and when it eventually arrived in Japan it shaped the culture dramatically. For hundreds of years rice was farmed in small, terraced paddies in the mountains of Japan. Dennis Normile writes about these traditional, rice paddies in a recent issue of Science. He describes how they were found in villages “nestled in a forested valley” accompanied by vegetable plots, orchards, and pasture. Today, farms like these are “endangered,” and as they have become increasingly abandoned, plants, insects, and other wildlife that have historically thrived there are suffering.

Since the 1960’s, a combination of factors has resulted in the decline of traditional rice farming in Japan. For one, large scale farming has led to the consolidation of paddies, which are farmed more intensively. Diets in Japan have also shifted, resulting in a preference for bread and pasta over rice. Additionally, Japan’s population is shrinking, and residents of rural areas are migrating to cities. Traditional rice farmers are aging, and younger generations are showing little interest in pursuing this career.

Red rice paddy in Japan - photo credit: wikimedia commons

Red rice paddy in Japan – photo credit: wikimedia commons

Demographic and dietary concerns aside, why in this case is the abandonment of agriculture imperiling species? The answer appears to be in both the way that the rice paddies have been historically managed and the length of time that they have been managed that way. Agriculture, by its very nature, creates novel ecosystems, and if the practice continues long enough, surrounding flora and fauna could theoretically coevolve along with the practice. When the practice is discontinued, species that have come to rely on it become threatened.

Traditional rice paddies are, as Normile describes, “rimmed by banks so that they can be flooded and drained.” Farmers “encouraged wild grassland plants to grow on the banks because the roots stabilize the soil.” The banks are mowed at least twice a year, which helps keep woody shrubs and trees from establishing on the banks. In some areas, rice farming began where primitive people of Japan were burning frequently to encourage grassland habitat. Maintaining grassland species around rice paddies perpetuated the grassland habitat engineered by primitive cultures.

As rice paddies are abandoned and the surrounding grasslands are no longer maintained, invasive species like kudzu and a North American species of goldenrod have been moving in and dominating the landscape resulting in the decline of native plants and insects. Normile reports that the abandoned grasslands are not expected to return to native forests either since “surrounding forests…are a shadow of their old selves.”

Additionally, like most other parts of the world, Japan has lost much of its natural wetland habitat to development. Rice paddies provide habitat for wetland bird species. On paddies that have been abandoned or consolidated, researchers are finding fewer wetland bird species compared to paddies that are managed traditionally.

The gray-faced buzzard (Butastur indicus) is listed as vulnerable in Japan. It nests in forests and preys on insects, frogs, and other animals found in grasslands and rice paddies. It's decline has been linked to the abandonment and development of traditionally farmed rice paddies. (photo credit: wikimedia commons)

The gray-faced buzzard (Butastur indicus) is listed as vulnerable in Japan. It nests in forests and preys on insects, frogs, and other animals found in grasslands and rice paddies. Its decline has been linked to the abandonment and development of traditionally farmed rice paddies. (photo credit: wikimedia commons)

All of this adds fodder to an ongoing debate: “whether allowing farmland to revert to nature is a boon to biodiversity or actually harms it.” Where agriculture is a relatively new practice or where conventional practices dominate, abandoning agriculture would be expected to preserve and promote biodiversity. However, where certain agricultural practices have persisted for millenia, abandoning agriculture or converting  to modern day practices could result in endangerment and even extinction of some species. In the latter case, “rewilding” would require thoughtful consideration.

The thing that fascinates me the most about this report is just how intertwined humans are in the ecology of this planet. In many ways humans have done great harm to our environment and to the myriad other species that share it. We are a force to be reckoned with. Yet, the popular view that we are separate, above, apart, or even dominant over nature is an absurd one. For someone who cares deeply about the environment, this view has too often been accompanied by a sort of self-flagellation, cursing myself and my species for what we have done and continue to do to our home planet. Stories like this, however, offer an alternative perspective.

Humans are components of the natural world. We evolved just like every other living thing here, and so our actions as well as the actions of other species have helped shape the way the world looks. If our species had met its demise early in its evolutionary trajectory, the world would look very different. But we persisted, and as it turns out, despite the destruction we have caused and the species we have eliminated, we have simultaneously played a role in the evolution and persistence of many other species as well. We must learn to tread lightly – for the sake of our own species as well as others – but we should also quit considering ourselves “other than” nature, and we should stop beating ourselves up for our collective “mistakes.” It seems that when we come to recognize how connected we are to nature we will have greater motivation to protect it.

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