Erica's Original Notes We, appearing so fragile, yet are more durable than the hardest stone by our capacity to adapt.
Yeasts use sugar and release alcohol and carbon dioxide; this carbon dioxide set the stage for a change to photosynthesis by mutations which gave some organisms pigments with which to absorb energy from the sun, so that they could synthesize their own sugars from CO2 and H2O, and were, therefore, no longer dependent on molecules for food; this process released oxygen into the atmosphere. (See Note 2 below.)
DNA (deoxyribonucleic acid) was present in even the simplest life forms; it was not, however, concentrated enough to be called a chromosome and merely 'floated' in the cytoplasm. (See Note 3 below.)
RNA (ribonucleic acid) is the messenger that initiates activities in the cytoplasm dictated by the DNA in the cytoplasm. (See Note 4 below.)
Algae: These cells act rather like a football crowd; they're all together, but they live separately, each in a waterproof coat, and fit into one of the following categories: a) with no nuclei, the chlorophyll being dispersed in cytoplasm; b) with nuclei containing chlorophyll in chloroplasts; and c) may be multicellular, as found in kelp.
Bacteria are a very ancient and primitive form of life; they are mononucleic and divide by splitting, with little genetic flexibility. They may form spores for survival under adverse conditions, and their reproductive rate is unsurpassed, as they have adapted to different circumstances. Some bacteria are parasites that feed on living organisms; botulism is caused by a toxin released by an anaerobic bacteria which is not killed by boiling. Saprophytic bacteria and fungi are the sanitary engineers of the earth, recycling minerals, water and oxygen, but NOT tin cans and plastics! (See Note 6 below.)
Fungi are more complex than bacteria; they also reproduce by means of spores which can live for months without food and water and are therefore resistant to external conditions. The fungi we see are really only the fruiting bodies producing spores. A webwork of threads (mycelia) lies deep within their host where it feeds on decaying material, unless it forms part of a lichen. (See Note 7 below.)
Mushrooms are our most visible fungi; the giant puffball contains seven trillion spores; the rust fungi has to have two hosts, such as Ribes and white pine or Berberis and wheat. The Berserkers of Norway may have savage attacks of madness after eating the Amanita mushroom (hence the etymology of 'beserk'). The fruiting bodies of mushrooms are usually above ground (epigeous), but some are underground (hypogeous) as with the famous truffles.
Lichen are the pioneers of the Plant Kingdom; in drying, they pull on the rock crystals where they are growing and are instrumental in the early formation of soil. It wasn't until 1867 that Simon Schwendener discovered that they were not only a form of plant life, but that they had a double identity! Fungi and algae work together in a symbiotic relationship: the fungi, who share with us and other animals their inability to make their own food internally, rely on the nutrients provided by the algae, and, in return, the fungi provide the algae with needed minerals and an anchor as a protection from environmental stress! There are many forms of lichen, but they can be classified into three main groups: crusty, shrubby or leafy.
2013 Updates (HM) 1) The rooting of the Tree of Life and the relationships of the major lineages are controversial. When we didn't know anything about DNA and scientific investigation, the understanding of life and our place in the universe was much simpler.
Until comparatively recently, living organisms were divided into two kingdoms: animals and plants, or the Animalia and the Plantae. By the 19th century, however, evidence began to accumulate that made it obvious that these two kingdoms were insufficient to express the diversity of life, and by the 1970s, a system of Five Kingdoms had come to be accepted as the model by which all living things could be classified.
A distinction was made between the prokaryotic (bacteria) and the four eukaryotic kingdoms (plants, animals, fungi, and protists (any eukaryote that isn't a plant, animal, or fungus)). The distinction recognizes the common traits that eukaryotic organisms share, such as nuclei, cytoskeletons, and internal membranes. Then, in 1970, just to confuse things further, the study of the DNA of simple organisms that inhabited extreme environments led to the identification of an entirely new group of organisms, the Archaea. Link: The Phylogeny of Life
2) Yeasts are eukaryotes and are more closely related to us than they are to bacteria. Like us, yeast cells have a nucleus and their DNA is arranged in chromosomes. Beer, wine and yeast raised breads all come to us courtesy of these hard working little single celled organisms
3) DNA (Deoxyribonucleic acid) is a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses. Along with Ribonucleic acid (RNA) and proteins, DNA is one of the three major macromolecules essential for all known forms of life. Studying the DNA sequence of organisms has enabled more accurate identification of the relationships between organisms than was possible by using visible characteristics. DNA sequencing has led to the reclassification and renaming of many plants, a fact which tends to aggravate many plant lovers. In the future, DNA barcoding with a hand-held reader (PlantMac?) may offer the gardener a fast and accurate identification method but not yet.
4) RNA (Ribonucleic acid) includes a large variety of important biological molecules that perform multiple vital roles in the coding, decoding, regulation and expression of genes within cells. RNA is not just a simple messenger as was previously thought, and knowledge regarding the variety and range of its role and functions within a living cell is a rapidly expanding.
5) Viruses: The name of this group of organisms comes from the Latin word 'virus' meaning 'to poison.' They contain only a message in the form of RNA or DNA and cannot reproduce by themselves. Viruses use their message to hijack the machinery of a living cell in order to replicate.
6) Bacteria are prokaryotes and do not have an organized nucleus. Bacteria are vital in recycling nutrients in the environment by breaking down organic matter and in fixing nitrogen from the atmosphere. There are typically 40 million bacterial cells in a gram of soil, and they are essential for a healthy environment. Bacteria can be genetically engineered to produce pharmaceuticals, such as human insulin for treating diabetes, and to breakdown harmful materials in the environment.
7) Fungi are eukaryotes and are more closely related to us than they are to bacteria. Fungi have cell walls that contain chitin and, like bacteria, perform an essential role in the decomposition of organic matter and the recycling of nutrients.