Are Blue-Green Algae Bacteria?

ARE BLUE-GREEN ALGAE BACTERIA?

Russell Nash

Blue-Green Algae, or Cyanophyta, are simple organisms that are believed to be the evolutionary link between bacteria and green plants. Fossils that are over three billion years old have been discovered in sediments and are concluded to be one of the first organisms to release oxygen into the atmosphere. Today, Cyanophyta are abundant throughout the world, found in salt marshes, on tree trunks, in fish tanks etc. Besides the typical bluish-green colour, Cyanophyta can vary from a blackish-green to an orange-yellow. As well as providing an evolutionary link, Blue-Green Algae serve an integral part of our lives with its importance in food supplements as well as its ability to cause economic damage via algal blooming. In this essay I aim to show the similarities and differences between Cyanophyta and bacteria using points of comparison, to answer the question whether Blue-Green Algae can be classed as bacteria.

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Blue-Green algae are prokaryotic, unlike the rest of the algae family, which can also be said for bacteria. Most of bacteria and Cyanophyta can only be seen through a microscope because they have only one cell and are around 1µm in diameter. In both bacteria and Cyanophyta, the cells have rigid walls. Bacteria have external flagella, which aid movement. Cyanophyta never have flagella. The DNA is able to float freely in a nucleoid in the cell, as they both lack distinct nuclei. Neither of the cells contains mitochondria, though Cyanophyta do contain centroplasts. Some species of Cyanophyta contain strands of cells rather than just being single cells. They are both accredited to be the first oxygen evolving phototrophic [that is an organism which can produce its own food from inorganic substances using light] organisms, although some bacteria can absorb their food from the substances of which they live on.

Cyanophyta and bacteria both help in the Nitrogen Cycle, by converting nitrogen that is present in air and soil into nitrogen compounds which can be used by plants, however bacteria also plays a vital role in the recycling of carbon, nitrogen, sulphur, and other chemical elements used by living things.

Bacteria are more useful than blue-green algae, and you can find them in the intestines of human beings and other animals. These bacteria help in digestion and in destroying harmful organisms. Intestinal bacteria also produce some vitamins needed by the body. Bacteria also cause fermentation, can purify water, useful in sewage farms, and they are used in the making of drugs. Because bacteria cells resemble other living things, scientists study bacteria to learn about more complex organisms. Most types of bacteria reproduce quickly and some species double their number every 20 minutes. If one of these cells were given enough food, over a billion bacteria would be produced in 10 hours. Industrial and laboratory processes often produce such enormous numbers of bacteria. But in nature, bacteria lack an adequate food supply to maintain such a high rate of reproduction.

Reproduction in both Cyanophyta and bacteria is asexual. This is achieved by single or multiple binary fission, budding, or trichrome fragmentation. When they reproduce by binary fission, the DNA in each of the two resulting cells is identical to the DNA in the original. Some bacteria can exchange DNA by conjugation, which involves the direct transfer of DNA from one type of bacterial cell, called a male, to another type, called a female. Bacteria also may pick up fragments of DNA from dead bacterial cells. By transferring DNA, bacterial cells transfer individual traits. Bacterial cells that are resistant to certain antibiotics may transfer this characteristic to non-resistant bacterial cells. This is not the case with Cyanophyta.

The first living things on the earth probably included simple forms of bacteria. The oldest known fossils are those of bacteria that lived about 31/2 billion years ago. This is around the same time fossils of Blue-Green algae have been dated to. Some scientists believe certain bacteria, such as Cyanophyta, gradually developed into multicelled organisms that were the ancestors of the more complex plants and animals of today. This, and the above similarities and comparisons, prove that Blue-Green algae can be classed as bacteria.

Bibliography:

http://school.discovery.com

Collins Advanced Modular Sciences Biology AS

Personal notes

Peer Reviews

Here's what a star student thought of this essay

skatealexia

12th of Jul 2012

Quality of writing

The candidate communicates well. Some parts of the text are hard to decipher because of the swing between comparisons and it is not clear whether it is the bacteria or algae that is being discussed, so care should be taken to make this clear. Punctuation, spelling and grammar are fine, with minor grammatical errors in places. The bibliography is not that useful because it doesn't state which bits of the text came from where.

Level of analysis

The introduction is to a very high level. The candidate discusses why there is the question about whether the algae are plants and also why the algae is considered important to humans. Rather than comparing why the algae may be bacteria in a solid text, I would have used a diagram of similarities to bacteria and differences so it is much easier to discern the differences as it is easy to get lost in the bulk of text. The candidate provides good comparisons to reach an adequate conclusion based on the evidence they analysed.

Response to question

Overall a good comparison piece. The candidate discusses the similarities and differences with very in depth scientific detail that I would expect of a candidate higher than GCSE level. Sometimes, because of the comparison the text can be hard to follow in places, but this is only a minor problem. The candidate conveys their ideas clearly.

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