The Ediacara

Before modern plants and animals, there were one-celled bacteria and eukaryotes. But was there anything in between? For a long time, people did not think so.


Enter the Ediacara

The Ediacara (also called Vendian biota) were ancient multicellular life forms that flourished for a "brief" 70 million years, and then disappeared. They were the first life forms to have distinctive cell types. They ranged in size from a few millimeters to more than a meter in diameter. They had a wide variety of body shapes, but did not have features such a mouth or internal organs. We do not know what they lived on, but speculate that they might have been filter feeders living on microorganisms, or they might have absorbed organic molecules from the water.

What was the world like in the time of the Ediacara?

At the time of the Ediacara, the world was dominated by a supercontinent, Pannotia. The rock record from that time is not very complete, so we do not know exactly what Pannotia looked like. Here is one idea of how the continents were arranged.

Pannotia

Pannotia had three parts, Congo, Proto-Laurasia, and Proto-Gondwana.

Most of Pannotia was located in the southern hemisphere. Over time the continents drifted towards the South Pole. This may have caused glaciers to build up on the polar continents and triggered the Gaskiers glaciation that ended the Ediacaran era.

Pannotia was surrounded by a super sized ocean, the Panafrican Ocean. The Panafrican Ocean was teaming with life, but Pannotia was sterile and lifeless. Life forms that could live on land had not yet evolved.

The Ediacara arose after the end of a period of world-wide glaciation, called the Marinoan glaciation. It ended with another great period of glaciation, called the Gaskiers glaciation

What Did the Ediacara Look Like?

The Ediacara life forms do not look like the plants and animals that arose in the succeeding Cambrian era. We do not know if the Ediacara were the direct ancestors of the Cambrian life forms, or a side branch of evolution that eventually died out. Other animals that lived during this time were sponges and probably tubeworms.

The Ediacara were very successful during their time on earth. Their fossils have been found in

• Namibia
• Charnwood Forest, England
• Ediacaran Hills, South Australia
• Mistaken Point, Nova Scotia

This picture shows an artist's idea of what Ediacara looked like in their natural habitat.

This Youtube video show Ediacara fossils. 

Here is a video of two guys looking at Ediacara fossils at Mistaken Point, Newfoundland. They are wearing paper shoes to protect the rocks. This area is now a protected World Ecological Reserve. 

For more about the Ediacara, go to http://en.wikipedia.org/wiki/Ediacara_biota

What are Cyanobacteria?

Cyanobacteria are bacteria that a capable of photosynthesis. They are are also called blue-green algae, but this name is misleading, since they are not true algae, but bacteria. The name "cyano" means blue, and refers to their blue-green color. Cyanobacteria are one of the most successful life forms that has ever existed on earth.


Small is beautiful


Cyanobacteria are a very ancient form of life, and existed more than 2.8 billion years ago. They are responsible for the modern world that we know today. In the early earth's atmosphere, carbon dioxide levels were 10-100 times higher than they are today, while oxygen levels were much lower than today. As cyanobacteria grew abundant, they reduced the amount of carbon dioxide in the atmosphere, and increased the amount of oxygen.


Other organisms that could not tolerate the presence of oxygen became extinct, or were confined to restricted ecological niches. For example, the bacteria that causes tetanus, Clostridium tetani, is anaerobic and can only survive in deep wounds where there is no oxygen.


Some forms of cyanobacteria can change color according to the light. In red light they produce more phycocyanin, and in green light, they produce more phycoerythrin. Thus, they appear green in red light, and red in green light. This helps them get the most energy from the available light.


What do cyanobacteria look like?


Cyanobacteria clump together in colonies of various shapes. Some form filaments, others form sheets, clumps or globes. Here are some pictures of cyanobacteria.

Stromoliths

Modern Stromoliths

Stromatoliths are large clumps of cyanobacteria. 

Stromatoliths are among the oldest fossils, and still exist today in Australia.  

Cyanobacteria shapeshifters

Cyanobacteria change form as environmental conditions change. 

• The normal photosynthetic cells are called vegetative cells.
• When conditions are unfavorable, cyanobacteria survive as spores,  that are resistant to harsh conditions.
• When oxygen levels are low, some types of cyanobacteria can form heterocysts, which can turn nitrogen gas into ammonia, nitrites or nitrates. Heterocysts have thick walls which contain the nitrogen reducing enzymes.
• Cyanobacteria can form mobile filiaments called hormogonia, that can travel and form new colonies. The cyanobacteria in the hormogonia are thinner than vegetative cyanobacteria.

Where are cyanobacteria located?

Just about everywhere! Cyanobacteria live in the ocean. They also live in fresh water ponds, lakes, streams and rivers. They live in damp soil, and in deserts after a rain.  They even live in Antarctica, and in glaciers, forming "green snow" in the spring. 

One of their most unusual habitats is the  fur of sloths in South America.  Cyanobacteria form a symbiotic relationship with fungi to form lichens. Lichens are able to survive on rocks, and are among the first inhabitants of new land.  

Descendants of cyanobacteria may also be living in every green leaf on the planet. 

It is thought that the chloroplasts in all green plants and red algae were originally cyanobacteria that were engulfed by other microoganisms.  This symbiotic relationship proved beneficial to both the cyanobacteria and the hosts, producing the green planet that we enjoy today.

What are acritarchs?

Acritarchs are microscopic fossils of any kind. They can be archaea, bacteria, or eukaryotes. They can be algae or even egg cases of small metazoa. The biggest acritarchs are about one millimeter in diameter. Acritarchs are a general name for these types of fossils when they cannot be more accurately classified. Once a more accurate classification is made, the organism is removed from the acritarch class.

The first acritarchs are found in the later Paleoprotozoic era. They are simple organisms, and are not very abundant. In the Mesoprotozoic era, acritarchs are more abundant and appear to be definite eukaryotes. They have ellipical shapes, processes, and appear in multicellular colonies.

Acritarchs from the Neoprotozoic era have a great variety of shapes and processes. Some look like modern fungi and algae. Many also had tiny spines. Some people think that the spines were for protection against early predators or grazers who fed on the acritarchs. Here are some pictures of acritarchs.

Snowball Earth

The snowball earth theory says that at least once during the earth's history, the entire earth was covered with ice. The end of the last period of world glaciation was 550 million years ago, and marked the beginning of the age of plants and animals. As evidence, scientists have found rocks that look like drop stones in ancient rock layers close to the equator. Drop stones are stones dropped by glaciers when they melt. The snowball earth is fascinating because it says that our planet has gone through extreme climate changes throughout its history.

Usually we say that Venus, which is about the same size as earth and is closer to the sun, is "too hot" for life to exist. Mars, which is smaller than the earth and farther way from the sun, is "too cold." The earth is "just right."

However, the snowball earth theory says that every planet is constantly subject to tug of war between the frozen cold of space and the inferno of magma within.

• The temperature on the Earth's surface is the result of many factors:
• The shape and location of the continents
• The amount of CO2 in the atmosphere
• The reflective properties of the surface - water, snow, rocks, plants

 The following three BBC videos explain the evidence for Snowball Earth. It is an exciting story of scientific detective work, and how scientists build on the work of others to better understand our past and our future.

 

Precambrian Era

Although it does not appear so large in the table, the Precambrian period actually made up 88% of earth's history. We know little about it, because there are relatively few rocks or fossils from that time.

In the 1800's, it was believed that life did not begin until the Cambrian era. Now we know that during long Precambrian period, microscopic life developed the biochemical and cellular foundations of life used by plants and animals

Cyanobacteria

Cyanobacteria are bacteria that a capable of photosynthesis. They are are also called blue-green algae, but this name is misleading, since they are not true algae, but bacteria. The name "cyano" means blue, and refers to their blue-green color. Cyanobacteria are one of the most successful life forms that has ever existed on earth.

Small is beautiful 

Cyanobacteria are a very ancient form of life, and existed more than 2.8 billion years ago. They are responsible for the modern world that we know today. In the early earth's atmosphere, carbon dioxide levels were 10-100 times higher than they are today, while oxygen levels were much lower than today. As cyanobacteria grew abundant, they reduced the amount of carbon dioxide in the atmosphere, and increased the amount of oxygen. Other organisms that could not tolerate the presence of oxygen became extinct, or were confined to restricted ecological niches. For example, the bacteria that causes tetanus, Clostridium tetani, is anaerobic and can only survive in deep wounds where there is no oxygen.

Cyanobacteria might have caused global glaciation or "snowball earth". As the amount of carbon dioxide in the atmosphere decreased, the earth became colder. The longest and most severe period of glaciation the earth has ever known was the Huronian glaciation 2.1-2.4 billion years ago. However, this period of extreme climate change may have been the stimulus for the formation of the first multicellular life forms.

What do cyanobacteria look like? 

Some forms of cyanobacteria can change color according to the light. In red light they produce more phycocyanin, and in green light, they produce more phycoerythrin. Thus, they appear green in red light, and red in green light. This helps them get the most energy from the available light.

Cyanobacteria clump together in colonies of various shapes. Some form filaments, others form sheets, clumps or globes. Here are some pictures of cyanobacteria.


http://www.abc.net.au/science/news/stories/s1441707.htm


http://serc.carleton.edu/details/images/2698.html

http://www.mbl.edu/news/press_releases/images/cyanobacteria2_brmma.jpghttp://www.mbl.edu/news/press_releases/images/cyanobacteria2_brmma.jpg

http://www.mbl.edu/news/press_releases/images/cyanobacteria_brmma.jpg

http://commons.wikimedia.org/wiki/File:Cyanobacteria_guerrero_negro.jpg


http://biodidac.bio.uottawa.ca

  http://www.botany.hawaii.edu/faculty/webb/BOT311/Cyanobacteria/CyanoHyellaStella300Crop.jpg

Stromatoliths are large clumps of cyanobacteria. Stromatoliths are among the oldest fossils, and still exist today in Australia.
 
http://www.nirgal.net/life_seek.html


Cyanobacteria Shapeshifters

Cyanobacteria change form as environmental conditions change.

• The normal photosynthetic cells are called vegetative cells.
• When conditions are unfavorable, cyanobacteria survive as spores, that are resistant to harsh conditions.
• When oxygen levels are low, some types of cyanobacteria can form heterocysts, which can turn nitrogen gas into ammonia, nitrites or nitrates. Heterocysts have thick walls which contain the nitrogen reducing enzymes.
• Cyanobacteria can form mobile filiaments called hormogonia, that can travel and form new colonies. The cyanobacteria in the hormogonia are thinner than vegetative cyanobacteria.

Where are cyanobacteria located?

Just about everywhere! Cyanobacteria live in the ocean. They also live in fresh water ponds, lakes, streams and rivers. They live in damp soil, and in deserts after a rain. They even in Antarctica, and in glaciers, forming "green snow" in the spring. One of their most unusual habitats is the fur of sloths in South America. Cyanobacteria form a symbiotic relationship with fungi to form lichens. Lichens are able to survive on rocks, and are among the first inhabitants of new land.

  http://www.sheridanmedia.com/news/community-colleges-quotpartnershipsquot-and-lichens13308

Descendants of cyanobacteria may also be living in every green leaf on the planet. It is thought that the chloroplasts in all green plants and red algae were originally cyanobacteria that were engulfed by other microoganisms. This symbiotic relationship proved beneficial to both the cyanobacteria and the hosts, producing the green planet that we enjoy today.

Timeline of Life

The history of life on earth is divided into four major eras.

During the Precambrian era, which actually lasted for almost 90% of the whole time that life has existed on earth, the only forms of life were microscopic single-celled bacteria and eukaryotes, and some early multi-cellular life forms.

The Paleozoic era was life before the dinosaurs - invertebrates, early forms of fishes, amphibians, and early reptiles and mammal-like forms.

The Mesozoic era was the age of dinosaurs.

The Cenozoic era is the age of mammals that has emerged after the dinosaurs became extinct, and continues to the present time.

In the chart below, you see the geological time periods, how long ago they existed, the animals and plants that emerged during that time period, and on the right, major continents during that period of time.

How Old Is The Moon?

'The moon is about the same age as the earth, about 4.6 billion years old. The "giant impact" theory says that a planet larger than Mars struck the earth. Most of the other planet and a large part of earth vaporized. Debris from the great explosion circled the earth and eventually coalesced into the moon.

Maybe before the moon formed, earth had rings like Saturn does today!

The moon is covered with impact craters.

The moon's surface shows striking contrasts of light and dark. The light areas are rugged highlands. The dark zones were partly flooded by lava when volcanoes erupted billions of years ago. The craters appear dark because sometime after they were formed, the basins were flooded with lava. That means that the craters were formed a long time ago, when the moon still had a liquid core.

The Far Side

The earth has about 80 times more mass than the moon. The pull of the earth's gravity has slowed down the rotation of the moon, so that the same side of the moon always faces the earth.

So human beings did not see the far side of the moon until the first pictures were sent back from an unmanned probe in 1959.

The far side of the moon is has many more craters than we see on the "earth side". One theory is that there was less lava flow to cover the craters on the far side of the moon. There was more lava flow on the near side of the moon because earth's gravity pulled the molten core off center. Learn more about this theory at: http://www.msnbc.msn.com/id/40135552/ns/technology_and_science-space/

Of course the obvious reason why there are fewer craters on the near side of the moon is that the near side of the moon received some shielding from the earth.