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.