The Great Lesson Journals

Friday, August 23, 2002

Wednesday, September 4, 2002

Thursday, October 3, 2002

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The Journal for Friday, August 23, 2002

This year I am back in my own room. I only have an assistant from 10 - 11 as NC has cut the budget. Every 35 students gets an assistant, so in our school we gave every Primary a full time assistant. Oh yeah, on top of the cut in the budget, we have a hiring freeze right now, so every 3 lower elementary classes is sharing one assistant as well, until the freeze allows us to hire one more. Life is so much fun.

Anyway, we moved to a beautiful location with lots of land to take walks and search for interesting stuff. Squirrels play in the trees and there is shade everywhere. This is such a change from our bleak beginning where lock downs were becoming a constant reality. It's too hot to really enjoy the outdoors yet, but soon we will explore every day. We now have 6 Primaries, 7 Lower Elementaries and 4 Upper Elementaries.

The first day, we did some general chores, explored the class and each other and then I presented the first Great Lesson. Here's the text. It has changed a good deal from the last one I wrote. I did away with the balloon as there is no sound in space. I was worried that the text might be too high, but the discussion proved me wrong. The class is really into the concept that atoms make everything. They decided they want special glasses so they could see. They discussed how everything would look alive this way as everything would be in motion. They are a high class this year, with many deep thinkers in the 3rd and 2nd grade levels. A younger class may have had trouble.

The Universe

When you were outside today what did you see? (Let students tell you.) This is a story about how everything came to be. A long, long time ago there were no people, no animals, no birds, no insects, no life on Earth at all. There were no waters to fill the seas, no trees to fill the forests, no air to fill the skies. There was no Earth, no Sun, no stars at all, no Milky Way - there was nothing and it was very cold. Actually there was something. It was a potential or a secret waiting to be told. Have you ever waited to surprise someone? Everyone is so still - an energy waiting to happen. Or think of when you were ready to jump up. Your legs are tense. This was the singularity. It was like a secret waiting to be told. It held a great power.

Now close your eyes and become very still. Now open your eyes and what do you see? Close them again and open them quickly. This is how our Universe was born. There was nothing and it was very cold and then there was everything and it was very hot. There was light for the first time.1 This candle represents the first light. The light came from radiation or photons, the particles of light. There were also particles of matter - the protons and neutrons and electrons and antiparticles. Now when scientists say everything appeared, they only mean these infinitesimal or very small particles; they do not mean that planets and couches and animals appeared. Our history began right then and continues even now into the future.

The Universe was very small and very hot. Particles were crashing into one another. They were wild and free and obeyed no laws. When the particles crashed into each other, they annihilated each other with a burst of energy called light. This picture is what it probably looked like. Clouds of matter with bursts of light where energy was given off.2. Luckily for life, the Universe was expanding and as it expanded it cooled just a bit. As it cooled, the particles of matter began to develop laws. The force appeared and the protons and neutrons began to slowly come together and formed the first atoms. Then these atoms joined with electrons and formed the element hydrogen which joined to form the elements helium. Now, when the photons of light crashed into them, the atoms allowed the light to pass right through. The Universe again became dark and rested.3.

When the Universe burst into being, it was not smooth like a balloon, but wrinkled. It was like your blanket or sheet on your bed. There were little wrinkles in time. The particles of matter began to get caught by these wrinkles and formed clouds. These clouds were what made the first galaxies. In the galaxies, there were places where a lot of particles were caught and they began to spin around each other and the temperature again began to rise. Suddenly, just as before, there was a great burst of light as the first stars were born.4 The Universe began to twinkle all over - in all the one hundred billion galaxies that filled its space. One billion years had passed.5

The earliest galaxies or elliptical galaxies are the oldest in the Universe. Their heat and life are almost past. The later galaxies are the spiral galaxies. These gas clouds have stars that continue to be born even today. These galaxies are special. There are over a billion galaxies in the universe and only a hundred million of these are spiral. One very special galaxy is called the Milky Way. Every star we see in the sky at night is in this galaxy. There are so many stars in our galaxy that scientists have calculated that if every star was one grain of sand, they would cover all the states from NC to Florida 200 meters high!6

Long ago, our galaxy had a special really huge star that was ready to end its life. A star is really a little factory that turns all the hydrogen inside it into helium. The light we see are really little photons of light or energy that is released inside the star. When all the hydrogen is used up, the star will expand outwards. This makes it really hot and gives the star enough energy for the helium to join to form carbon. The star then can shine with a brighter light. When all the helium has been turned into carbon the star again will expand and the carbon will join to form oxygen. This will continue until neon, sodium, magnesium, aluminum, silicon and finally iron are formed.7 This is a chart of all the elements now on Earth. Every element has come from the stars. This is why scientists say everything is made of star dust. When a really big star has used up all its energy it expands into a red giant and then boom! The star goes super nova8. This is a picture of a supernova. All the elements inside the star are shot out into space along with a lot of dust and gas. 9 This is called the interstellar matter. Then, the galaxy slowly, slowly, again gathers this interstellar matter together until a new star is born.

Four billion years ago a new star, our Sun, was born10. It is only a medium star, but it is still one million times bigger than Earth. 11. So why does our Sun looks so small? (Wait for answers) Do you know how long it takes the light from our Sun to reach us here on Earth? 8 minutes. Do you know how fast light travels? 186,000 miles per second or 11,160,000 miles per minute. Light travels so fast that it can go around Earth 7 times in one second.12 If I had a super car and drove at 100 miles per hour without ever stopping to rest, it would take me 10 days and 10 nights to get around Earth. Our Sun must be very far away if light takes 8 minutes to reach us. This means that every time we look at the Sun, we are seeing 8 minutes into the past. This is why the telescope Hubble can see the past - it gathers light from so far away, it has pictures millions of years old.

When our Sun was formed, some small discs called protoplanets13 remained and they continued to gather matter until our nine planets were circling the Sun. All spinning and rotating just as the force required. In the beginning, all the planets were molten or gaseous. The elements first huddled together, but they got too hot and expanded out to space to cool. Then they contracted and raced back to huddle in the center. Expanding to space - contracting to huddle - this continued for millions of years until finally the smallest, closest planets, Mercury, Venus, Earth and Mars settled.

Finally, the heaviest elements sank to the core while the less heavy elements stayed in the middle and the lightest floated on top.14 All the other rocky planets remained this way, but one planet was special. This was our blue pearl that came to be called Earth. At first, Earth was still hot - so hot that the rains that fell sizzled quickly back out to space. Gigantic electrical storms flashed across Earth with immense lightning bolts filling the skies. This continued for hundreds of millions of years until it was cool enough and then the particles assumed three different states of matter: Solid in which the particles hug each other tightly, liquid in which the particles hold each other, but not so closely and finally gas which just runs off in all directions.14

At last, near the end of this first story, Earth cooled enough for rain to reach the rocky crust. Pools of water formed, then ponds, then lakes, then immense oceans. At times, though, the molten elements from deep beneath the Earth's crust still sprang out15 - the minerals and gases from deep in the Earth mixed with the waters of the oceans and the minerals from the rocks. The Earth was ready for the next story, but that story will be told another day.

1. Light a beautiful candle

2. Picture of early universe

3. Blow out the candle

4. Light the candle again

5. Picture of galaxies with stars twinkling

6. Sand and meter stick

7. Chart of Elements

8. Supernova

9. Matter rushing out of a supernova

10. Our Sun

11 Globe

12. Hierarchy cube and unit

13. Picture of protoplanets - then chart of planets

14. Solid, liquid, gas

15 A volcano / baking soda, red food coloring, vinegar

My favorite question was a second year boy who asked me later how wide the path would be if the stars were lined up form NC to Fla....

I really liked the poem that circulated on the Montessori List this summer, so the second day I read it to them and then I offered my class the opportunity to do a play. As our research won't be ready for a while, we could just put on a play instead. This logic has proved slightly lacking as the play has put our research off even further, but it has been fun. Our new school has a full blown auditorium with a huge stage so they jumped at the chance. This is what we came up with. I divided the students into stanza's and then had our cool TD teacher come and work with each group to brainstorm ideas. Our new art teacher is Lower El trained as well, so after her initial surprise that I had already organized a project for her, she jumped in whole heartedly. I got the general language and math of the class going and then the students and I met to discuss ideas and polish them after lunch each day. We will perform it this Friday to parents and other classes of the school. Wish us luck!


(house lights go down)

Welcome to our first presentation.

We are performing a poem adapted by Ms. Barbara from Earth History by

Vera Edelstadl.

We would like to thank Ms. Susan and Ms. Trish for their help.

We hope you enjoy the show!


Stanza 1

Speaker 1

(lights go off)

About five billion years ago

(spots go on)

The Earth and all its friends were formed. Whirling, burning balls of gases

(students whirl across stage)

Spinning madly off in space

(students whirl across stage)


Speaker 2

Melted rock and molten metal swirling formed a white, hot ball

(students swirl to center and form ball)

They spun around, along with gases;

(students spin in circle)

Then settled in their final form

(students kneel in a line - put heads down)


Speaker 3

Granite floated on the top; iron sank down to the core

(some students stand up, some stay down)

Finally, the granite cooled to make a solid crust of stone.

Stanza 2

Speaker 1

(volcanoes on stage)

Volcanoes spurted like flaming daggers;

(volcanoes spurt)

The Sun flung down its blistering rays

(Sun walks out and flings his rays)

Earth was scorched with blazing heat; rain evaporated back to gas

(rain does dry ice)


Speaker 2

Meteors came from the sky; no atmosphere to burn them up

( meteors are thrown at the mural)

A large one may have helped to form the moon that circles Earth today

(Moon rises)

Stanza 3

Speaker 1

Finally, the Earth had cooled, enough to let the rains pour down.

(rain )

Storm clouds wrapped the Earth in darkness

(storm clouds wrap the mural)

Lightning cracked in jagged patterns

(lightning bolt comes out)

(thunder crashes cymbals)

(student sneaks out and lowers second mural - sneak back)

Nothing lived on Earth to notice; wet, bare crust, that's all there was

(students part and point to the mural)

Then one day the rains did stop

students leave)

The clouds grew thin and light did shine

(Sun come out and shines - then leaves)


Stanza 4

Speaker 1

Still there was no life on Earth; just rocky crust and restless oceans

In the oceans, conditions were right, the Hadean Era was at its end

Another story now needs to be told

(student carries out poster of Life)]

(student returns to stairs)

All bow


student - Thank you for coming. We hope you enjoyed our poem

Costumes and props

Swirling balls of gas: paper plates with streamers of curled ribbon

Paper plates have granite and iron written on top so when they kneel words are visible

Volcanoes have gloves died red with streamers - cones around their bodies

Sun sandwich with Chinese yo-yos for rays

Dry ice for evaporated rain

Meteors are crumpled paper

Moon picture

Rain is purchased table skirt of silver paper cut into strips

Storm clouds are fabric wrapped around bodies

Lightning is cardboard; thunder are cymbals

Sign with life



Mural with a picture of Earth as a gaseous planet

Mural of barren Earth Body

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The Journal for Wednesday September 4th

Well, we performed the play on Thursday and Friday. We performed on Thursday for the Primary and half the Upper Elementary. I led my class out of the auditorium first and as they exited the building, they exploded with enthusiasm. They knew how much work it was to practice and how going over scenes could be tedious - although they took the practices with excitement and good concentration - but after performing for a large audience, they were full of energy. Yes! they almost simultaneously exploded, "That was so much fun!"

The next morning we performed for the Lower Elementary and rest of the Upper El. This time there was a definite lack of concentration and talking on the steps where they awaited their turn. A parent made a video of the performance so after our music special we all went to watch the show. They could easily see their mishaps and hear voices. So, when we performed for the parents that afternoon, they were amazing. The same parent taped the play again and I hope to watch it next week and make copies for anyone interested. They exited the stage telling me that now they were true actors.

They have learned that a play takes work and planning, that control is important; that the audience can be distracted from the action by loud noises and that a play is ever so much fun.

Next week, the third graders have their first round of testing, we begin the Time Line of Life and definitely settle into work. I have decided to talk about each era on a different day and then show the Time Line of Life as a finale. I'll see how it goes. I have the most wonderful pictures of animals form each period that I have copied from the Internet. Some students are already researching reptiles of the oceans and dinosaurs from the different eras, but I have not noticed the first year students noticing when the time line has been put out. They are kind of in a wandering fog overwhelmed by the big thoughts and play.

This is the text of my new second Great Lessons:

The Precambrian Period: Age of the Archaeans and Cyanobacteria

So what was Earth like at the end of our first story? (They should note that the crust had formed, rains had fallen and formed the great oceans and that lightning storms raged over the Earth.)

The Hadean Era was over. Earth was about 1 billion years old. Most of the land was covered with immense oceans that were warm and thick with minerals. There was an atmosphere, but it did not look like our sky of today. It was orange and did not offer the protection we have today; it just let the sun's rays shine right through. It was hot and Earth smelled of rotten eggs. This was the Archaean Era.

Rain does not seem like a strong force to most of us unless we live where floods occur, but it is an important force on our Earth. When rain fell, it washed tiny bits of minerals out and carried them along to the immense oceans. These minerals filled the seas and turned the water murky. Scientists think that as lightning struck the water, the most amazing event ever to occur on Earth happened.

Life appeared. It was microscopic and very simple. It followed new laws that all life would follow ever after. It ate, made more of itself and changed just slightly over time. This tiny life was all alone on Earth for over 1 billion years, but it filled the oceans. This new life later came to be called the Prokaryotes.

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The Journal for Thursday, October 3, 2002

Well, I haven't written for a long time and never did get the second journal up, so here's a third. The students loved the pictures and I think discussing each period before the Timeline of Life presentation really worked. When I did get to the Timeline, they had enough previous knowledge that although they still were so excited about the pictures of life, they could better discuss the totality of the Timeline.

We then went on to Early Humans and I presented it in much the same way as outlined in last year's lesson. We are still working towards the History of Writing. I expect to get there Monday at the latest.

The second grade reports on planets will happen on Friday. They are ready and excited and have finished their models. We have been making fossils out of Plaster of Paris and making great rubbings of early creatures with some work I picked up from some Montessori company - lots of help aren't I? I think it cost under $10 and it was four plastic sheets of different eras that could be rubbed. Some of my students have figured out how to make beautiful scapes. The first graders have just started research. Some are doing volcanoes, two are researching Hubbell - very teacher led, but they love the pictures, and some are doing earth's composition. I just let them choose. Many of the third graders are being edited - they have worked very hard on dinosaur reports. Carnivores, Hadrosaurs and reptiles of the sea have captured their imaginations.

The class is rolling and now the usual problem of slowing it down enough to get more lessons in.

We're having a scary story party. Everyone is writing scary stories - I haven't read them yet. We're having scary snacks, wearing red and black clothes and decorating our class as a dungeon. (All student organized of course.) I'm excited as my class has never organized such a happening before. It should be fun.


In the beginning Earth was hostile. The sun beat down strongly as there was no protective atmosphere. The water were hot from the sun and erupting volcanoes. The first kind of Prokaryote or bacteria as they are sometimes called, were probably the Archaeans. They developed to live in the unpleasant places on Earth and still live there even today. They did not mind the intense heat or murky water - as a matter of fact, they love these conditions and a few still live in the worst places on Earth today - at least by our standards... Most of them used the mineral sulfur - that rotten egg stuff - that washed off rocks for their energy. Soon there were so many of them filling the oceans that food started to disappear. They were eating the chemicals in the water faster than the rains could wash them away from the rocks above. Some changed, just a little bit at a time, but finally some could eat the waste of their friends and some became carnivores and ate their friends.

Others looked to find another, easier way to get food. Some looked at all the sunlight high above them and made another small change. They came to be called the Eubacteria. They ate the Sun's light. A special Eubacteria was the Cyanobacteria. It has chloroplasts just like plants. They used the Sun's energy to make their food and then gave off oxygen into the water. Earth's rocks took in this new elements at first and all the rocks turned bright red as they made iron. The Cyanobacteria now filled the seas. Soon the rocks had taken in as much oxygen as they could, so the oxygen was free to go off into the atmosphere.

The Archaeans did not like this new atmosphere; it was poisonous to them. Some hid under the Cyanobacteria that grew in huge mats on the surface of the ocean. The Cyanobacteria protected their brothers and sisters. Eventually these mats hardened into great stromatolites that lined the edges of the new continents. They were the first coral reefs. Other Archaeans were eaten by their brothers and sisters, but they did not disappear. Instead, they lived inside and made this new bacteria have even more energy. This is like our cells today. The stromatolites filled the seas along with their other bacterial brothers and sisters until about 600 million years ago when the mats of stromatolites slowly began to disappear. What caused them to almost disappear?

Scientists have a few clues. Strange fossils have been found of unknown organisms. Scientists have named them Ediacaran organisms as they first found their remains in the hills of Edicara in Australia. They did not resemble anything ever found before in fossil records and scientists do not at all agree on what they were, but they did exist in oceans all around the world. They have named this short time the Vendian Period.

Some scientist think they were one-celled animals that swelled up to huge sizes. They may have absorbed oxygen and nutrients directly from sea water or bacteria may have lived inside them and helped make their food. Or they may have nibbled on the Stromatelites. Others have different ideas. They think the fossils that looked like disks could have been jellyfish, frond shapes were possible animals like Sea Pens, which are relatives of the Sea Anemones. The flattened forms, which look like squished chewing gum, could have been a type of annelid or worm. Then again, they may have been a kind of lichen. We don't know, but they did live and there were many different kinds and they may have gobbled up all the Stromatolites.

During the Precambrian Period, the continents had been moving to form supercontinents, and then broken up into smaller pieces as they moved over the mantle. The Earth had passed through at least three Ice Ages. Now, at the end, Earth again became very active. There were many earthquakes and volcanoes and the huge amount of ash that was spewed out caused Earth to cool again. Great glaciers began to cover the Earth in a new Ice Age. A new supercontinent that scientists have named Rodina was formed. Many life forms, including the Edicara went extinct.

As the Precambrian Period came to an end, Rodina began to split, forming the Panthalessic Ocean. The Earth was about to explode, but not with volcanoes this time.

(I downloaded pictures off the Internet of the vendian animals and showed enlarged pictures of bacteria.)

I love to talk about bacteria separate from the Time Line. I have done this for several years now and it has been very successful. Bacteria was mysterious to the young child as they cannot be seen, but they do know about their effects and have heard about 'germs' all their lives. One third grader clapped his hands and told me he had just killed millions of bacteria - no, I replied, they are so tiny, they can fit in the nooks and crannies of your hands. He looked at his hands intently. We also talked about how they come in just 3 shapes, although there are so many kinds. Every year we grow bacteria in petrii dishes. We with our cu-tips to our bodies or places like the bathroom or tables or books and swab away. Wait a week and gross!!! Keep the tops on and throw away when done.

Over the week we talked about the Paleozoic Era. I had downloaded realistic pictures of life in the seas from the Internet. They loved the pictures - it makes the story more real. Then on Friday I showed the Time Line and finished the story and when you talk about dinosaurs, they are gone anyway. I really liked telling the stories separate from the timeline. They listened more and we got into more depth. The middle of next week will be Early Humans.

Here's the rest of my text. Remember to put it in story form - this is more an overview for the teacher based on newer research. Do be sure to talk about the special gifts each phylum has given to life. This plants the seeds for the Gifts of the Phylum work. I ask a lot of questions so the students give most of the story and I elaborate on their knowledge. I want the young uns to know that this is a story that they can know - it is not adult knowledge.

Paleozoic Era

Paleozoic means old life. Most of the life on Earth developed in this Era. It is broken up into six periods; the first of which is the Cambrian Period. It is known as the time of the explosion of life. Over 900 species have been recorded. One of the reason scientists have been able to learn so much about these new animals is that so many of them had hard shells made from the minerals that filled the seas.

Almost all life was invertebrate or without an internal backbone. All life lived in the great oceans, although some bacteria probably ventured onto land. There were many animals that would look familiar to us today.

The Porifera were probably one of the first animals to float in the Cambrian waters. They are the sponges. Sponges are many tiny organisms that work together as one. If you take a living sponge and put it through a strainer, it breaks apart, but given time, all the organisms will again come together as one. This cooperation between cells was happening everywhere in the seas.The Cnidarians (ny-dair-ee-ans) were probably the first animals to move. They are now the jellyfish, corals, hydras and anemones. They have two layers of cells, nerves and muscles, that work together to move. They do not move with a purpose, however, but just float in any direction they happen to go. They also have specialized cells in their tentacles that can sting its prey. They do not hunt their prey, however, but just wait until it comes along.

The Platyhelminthes (pla-tee-hel-minthes) were probably the first active hunters. They are the flatworms. They have three layers of cells. They have a simple brain and a nerve cord that runs the length of their body. They have bilateral symmetry like we do, a head, and a tail. They do not have eyes, but they do have cells sensitive to light called eyespots. They can go out and actively search for food.

The most successful animals in the Cambrian seas and forever after in our world were the Arthropods. The crustaceans are the marine arthropods or lobsters, crabs, shrimp and barnacles. The name Arthropod means "jointed foot" as they can bend their legs. All arthropods have segmented bodies and are covered in protective armor called an exoskeleton. Their body muscles attach to the inside of the exoskeleton. In order to grow, arthropods must molt or shed their shell or exoskeleton and then grow a new shell. They developed the most amazing specialized cells: antennae, claws, wings, shields, and mouth parts

The Trilobite was the arthropod that filled the Paleozoic Seas to its end. It had three lengthwise segments on its body and came in many different sizes. In the Cambrian Period most of them lived on the ocean floor, but a few actually swam in the water. Some may have been predators eating other, smaller animals and some may have scavenged or eaten dead animals. Some of them had eyes like the insects and crustaceans of today.

The Mollusks developed the best defense against these new predators. They are the clams, snails, slugs, nautiloids, squid and octopus. They built shells around their bodies. Their shells have chambers filled with water and air which can be adjusted to let them sink or rise in the water.

The Echinoderms are the Sea Stars, Sea Lilies, Sea Urchins, Sea Cucumbers, and Brittle Stars. They developed in a totally different, but still successful way. They become radial with five-part symmetry and no central brain. They have tube feet that cover their five legs. These tubes are what they use to move and to pry open their favorite mollusks. They do not have any muscles at all. Their bodies are made of hard plates that are often spiny and covered by a thin skin. Most have a very special ability; it's called regeneration. They can grow back a leg that has been cut off..

The Annelids are the earthworms, leeches and bristle worms, may be thought of as lowly worms, but they are impressively powerful and capable animals. They also have a most important job in that they help to break down bits of rock and dirt and dead plant and animal matter into soil. This process releases carbon dioxide into the air or water. Today carbon dioxide helps land plants to thrive. Annelids all have ring-like bands along their muscular body called segments. This is why they are called segmented worms. They have a circulatory system to distribute blood and oxygen and both a mouth and an anus. Now food could be continuously taken in the mouth and digested without stopping to spit out the remains. Annelids creep along or burrow. The sea floors of the Cambrian period were full of these small, burrowing animals.

There was one other animal in the Cambrian seas that is worth talking about. It was an eel like animal, but it was very special for our own history. It was a Chordate. We are vertebrates as we have a hard bony part of our skeleton that protects the main nerve that comes from our brain. The Pikara had a one main nerve running down their back with muscles on either side. It also had a stiff rod that ran down its center called a notochord. So scientists think these were the very first chordates - our ancestors. It lived 500 million years ago.

Every Period thereafter has brought some new change that caused certain types of animals to survive while others went extinct. The Ordovician Period brought new, fierce predators. A huge cephalopod mollusk called the Nautiloid had its arms on its head. Some grew up to 30 feet long. It had tentacles with sticky suckers to seize its prey and a hard beak to break open shells. In the next period called the Silurian, the most ferocious predators were arthropods called the Sea Scorpions. The largest, the Pterygotus, grew to 6 ft long. It had very sharp pincers on arms in front of its mouth and had a tail and side arms that could move it through the water. Its eyes were very large. In response, the trilobites which still filled the seas, developed harder, thicker shells or learned to roll up for protection.

Another chordate, this one in a special subphylum called the vertebrates, appeared toward the end of the Silurian Period. These were the jawless fishes scientists call the Agnatha. They lived at the bottom of the seas and sucked up small particles of food. The first jawed fish also appeared. They had spiny fins that may have helped to protect them from predators. Most of the jawed fish had teeth to grab their prey with. These jawed fish developed scales like modern fish.

At the end of the Silurian Period another great event that was to change Earth forever occurred. Seaweed, brown, red and green algae, had flourished in the shallow waters around the coasts of the continents. They formed huge beds which sometimes washed up on the shore. Some of the green algae developed a way to protect itself from drying out. It was a waxy surface called the cuticle. The cuticle had small openings that still let carbon dioxide in and oxygen out so they could live. They developed roots that searched the land for minerals and tubes to transport water. They were not very tall, just like our mosses today, but they began to slowly transform the land.

By the Devonian Period a carpet of green plants now spread across the land. At first, they had no leaves and grew only to about 7 inches, but by the end of the Devonian, they developed into great forests of lycopods. As the plants grew more densely, the Sun's light was blocked so some grew taller and developed a woody tissue to help support their long stems - not bark as we know today, but more like the scales of reptiles. The plants began to break up the rock with their roots and when the plants died, fungi that had joined the plants and bacteria began to break them up mix it with the rock. Earth was slowly covered with soil..

Small arthropods soon began to move out onto the land to take advantage of all this new food. The larger predator arthropods soon followed them. The land now swished in the breezes and small chomping and rustling noises filled the air.

Fish continued to change and filled the seas. They came up with all kinds of plans to help in their survival. There were fish with heavy armor, fish with scales, fish with jaws, fish without jaws, fish with cartilage and fish with bones. Some of the jawed fish had sharp plates in their mouths. They could throw back their heads and open their jaws wide and then crunch down on its prey. They had the power to attack anything. They are called the placoderms and some grew to 11 feet. The first sharks had streamlined bodies and large fins to swim fast. Rays also swam in the seas above. Toward the end of the Devonian, the bony fish - the osteichthyes - appeared. They had a swim bladder to help them move up and down in the water. This swim bladder would later become lungs. Most bony fish have fins made of bones (ray finned fish) but a few have a more fleshy fin. These are called the lobe-finned fish.

These lobe-fined fish became very important in the history of life on Earth. They had two pairs of fins - one in front and one in back. They used these lobe fins that had bones very much like our hands and feet to pull themselves out onto land in search of the plants and insects that now made their life there. Water provides animals with a lot of support, and air provides little, so these fish had to change a bit more before they were ready to join the arthropods entirely on land, but change they did and during the Carboniferous Period they crawled out onto land to eat. They became known as the amphibians. They, too, evolved into many different forms. Some were huge and lived much of their lives in the water, some were small and ate the insects scurrying about in the forests. Some had no legs and burrowed into the mats of plants that covered the floor. All stayed close to the water that had been their home.

The Carboniferous Period is named for the coal which came from the lush, swampy forests. The forests were now thick with trees reaching even 150 feet high. Insects swarmed everywhere. And spiders and cockroaches scurried about along with grasshoppers, beetles centipedes and millepedes. Some insects developed wings and buzzed through the trees to escape their predators. The dragonflies grew up to 27 inches. Butterflies and moths soon followed, but there still were not enough organisms in the soil to break down the great amount of dead plant matter on the forest floor so it began to form huge mats. By the end of the Carboniferous much of the land was again covered by seas and huge swamps. The dead plants and animals now began their journey to become coal.

The Carboniferous Period ended with a new plant called the seed fern that produced seeds which were carried by the wind. Now drier areas of the continents would be covered by plants as well. A new animal also made its appearance: the reptile. Most were small and looked like our lizards of today. Now they too wandered through the forests.

The Paleozoic Era was about to end. The Permian Period began with the arrival of the early reptiles. They still had their legs out to the side and they were small insect eaters, but they could go out into the forest far from the water's edge. By the end of this Era, huge reptiles wandered over the land. Some had developed huge sails on their backs and some were ferocious carnivores. Others had returned to the seas and developed flippers.

A few, called therapsids, evolved legs that grew directly under their body. This allowed them to run and move faster. As they held their chest higher, they did not need to rest to breathe. Some became warm blooded so that they could adjust their body temperature without the Sun's help. This meant they were active for longer periods of time. A special synapsid developed teeth just as mammals have today: sharp, front incisors for grasping and biting and flat molars for chewing. They also developed the ability to breathe while they chewed, so they did not have to swallow their food whole. They may have even had fur to keep themselves warm.

Life had evolved to fill every niche and cranny. Every animal had a particular job to do. They had developed special methods of either escaping those that wanted to eat them or to be able to eat what they wanted. Then something happened on Earth. Scientists are not sure what - it may have been that huge mud slides from volcanoes filled the oceans, making it hard to breathe or maybe a huge asteroid hit the Earth blocking off the light or maybe the animals just could not adjust to the great formations of mountains which was causing a very the dry climate. In any case, there was a great extinction, the greatest that has ever occurred on Earth. The extinction was spread equally across land and marine environments. The trilobites were never to appear again. All the large amphibians and many smaller ones went extinct and many of the old plants that relied on water were wiped out.

The next direction life was to take on Earth was perhaps not the most important, but it was certainly exciting.

Mesozoic Era: Age of Reptiles

Mesozoic means middle life. It is divided into three periods: the Triassic, Jurassic and Cretaceous Periods. The end of the Permian left many parts of Earth uninhabited and those that were left quickly evolved to fill in.

While some of the reptiles in the Permian Period had developed extra skin to glide with, in the Triassic Period reptiles called Pterosaurs developed a new wing which had skin stretched over elongated ribs. They glided high over the cliffs. A new reptile called the thecodent also appeared. They came out of the water to live on land, so at first they moved much like a crocodile with its legs out to its sides. As it adapted to life on land, its legs moved under its body and these new rulers of the land became the strongest walkers and runners Earth had ever seen. They would usually walk on all fours, but when in a hurry they would lean back, use their tail to balance and run on their strong hind legs. They had a hole in their hip socket and a right angle bend at the top of their thigh bone. The dinosaurs were about to rule the world.

The Jurassic Period saw a return to the lush, green Carboniferous world. Cycad and conifer forests again spread away from the edges of lakes and rivers to again cover the land. New oceans formed as the continents again started moving apart, and the new continents gave sea life more shallow edges to live on. Great coral reefs sprang up and octopus and squids appeared. Insects also evolved quickly into new species: ants, bees, flies, wasps and others quickly filled the new forests.

Reptiles still dominated the land. Huge sea reptiles hunted in the sea alongside the sharks and bony fish. Other reptiles developed long necks so they could stand at the water's edge and fish. Turtles, crocodiles and tortoises appeared. As the continents were all joined into Pangaea, great herds of plant eaters could roam over great span of land. Huge birds called Pterosaurs filled the air. Their bones were now hollow and their teeth had disappeared. The most common dinosaur of the Jurassic were the sauropods. These were huge lumbering dinosaurs that had necks like giraffes. They spent their day munching on the leaves found in tall trees. There were also giant, carnivore dinosaurs. They walked on two legs and their toes each had large, powerful claws. The front legs also had long, clawed fingers that could have easily ripped open a prey's neck. At the end of the Jurassic Period, true birds with feathers evolved. They still had small claws on their wings. Some may have slept upside down as bats today do.

The oceans of the Cretaceous Period saw the appearance of lobsters, crabs and shrimp. The land now saw the appearance of snakes and seabirds had evolved to feed on fish. Flowers now worked with the insects to spread their pollen and this caused an explosion of flowering plants to spread over the land masses. Today there are 250,000 species of flowering plants, but only 50,000 species of other plants altogether. This shows how successful they were.

Duckbill dinosaurs called the Hadrosaurs were the dominant grazing dinosaur. They also lived in herds. There were also Stegosaurs and the Ankylosaurus Crests, frills, spikes and strange horns were even more elaborate than in the Jurassic Period. The Triceratops made its appearance right at the end of the Cretaceous Period. It did not walk the Earth for long.

Cenozoic Era: Tertiary and Quaternary Periods

The Cenozoic Era which means new life is broken into two periods. The bony fish and sharks remained the greatest carnivores in the sea. On the land, the mammals began to fill in the gaps left by the extinction of the dinosaurs. Most early mammals had been small insect eaters that mostly came out at night when the dinosaurs were less likely to be active. Mammals now diversified. Some lived in trees like today's squirrels, some ate carrion or dead animals, large herbivores and carnivores appeared. Some had tusks and some developed horns just as the dinosaurs had. Some returned to the sea to take the place of the huge reptile carnivores that had gone extinct. Penguins, ducks, gulls, herons, pelicans and later, parrots, pigeons, woodpeckers, crows and falcons were common.

Another group of mammals that would soon rule Earth developed. They were the placental mammals. They kept their young inside them until they were much more developed. These young had a much better rate of survival. They spread to all parts of the world. Today there are 4,000 species of placental mammals which have adapted to the driest, wettest, coldest and hottest areas of Earth and have adapted to both the air and the sea.

Moles, poisonous snakes, rabbits, camels, mice, rats, guinea pigs, porcupines and voles appeared, and finally at the end of this epoch the cats, dogs and bears evolved. The largest land mammal to ever live was the Megistotherium. Its head was twice as big as a grizzly bear's. The Diatryma was a flightless bird that was seven feet tall. It had a huge parrotlike beak that could tear its prey to pieces. The first elephant appeared, although it looked a bit more like a pig with a long nose. The first horse was about the size of a fox.

Herbivores began to increase with the new increased grassland areas. The rhinoceros, pigs, cattle and deer appeared. Edentates appeared in South America - they are the toothless mammals like the anteaters, sloths and armadillos. The horse lost some of its toes and grew taller while the elephant grew tusks. These herbivores continued to increase in numbers. Some herbivores developed larger teeth for chewing grass and a system of stomachs that allowed them to regurgitate their food so they could chew it later when in a safe spot. They also developed eyes on the sides of their head so that they could see all around for protection from predators.

Monkeys appeared in South America, Asia and Africa while apes lived in Africa. They developed a new system of seeing that allowed them to see three dimensionally. This helped them to judge distances when they leaped from branch to branch. They had larger brains than the other primates and took longer care of their young who had much to learn. The Quaternary Era began 2 million years ago and continues through today. Today we live in an interglacial period or a time in between an Ice Age. After the last Ice Age, many animals became extinct. Scientists are not sure if the cold was to blame or if a new, more adapt hunter had caused their extinction, but that is a story for another day. That is the story of a special mammal named Homo Erectus.

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