Essay Sample Fossils are the remains or marks of plants and animals that lived a very long time ago. They are usually found in rocks and stones. Fossils are important because they tell us a story about things that lived on the earth before blogger.comted Reading Time: 6 mins Page 1 of 50 - About essays Body Fossils and Trace Fossils Fossils can be divided into two categories, body fossils and trace fossils. Body fossils encompass preserved remains of an organism, such as bones, claws, teeth, skin, embryos, Fossil Tiktasalik Essay Words 3 Pages The author and his colleagues chose to focus on million year old rocks in their search for fossils because amphibians that look dissimilar to fish were discovered in million year old rocks, while fish without amphibian characteristics were discovered in million year old rocks
Essay on Fossils: Top 6 Essays | Fossils | Palaeobotany | Botany
Essay 1. Thus, a fossil refers to anything that is excavated from the earth and not fashioned by man. Actually, the fossil refers fossil essay organic remains taken from the earth. So in common sense, fossil essay, fossils are the traces of the past life forms in the fossil essay of the earth, fossil essay.
Essay 2. These are the remnants of organic compounds p reserved in sediments or in parts of fossilised structures without undergoing any or minimal change. These include amino acids, hydrocarbons, fatty acids, lipids, carbohydrates and the derivatives of other organic compounds. The chemical composition of Pre-Cambrian rocks is an important criterion to establish the biogenicity of putative unicellular or multicellular organisms present in Pre- Cambrian rocks.
The existence of insoluble kerogen is used as proof of biogenicity. Similarly, the occurrence of pristane and phytane, degradable products of chlorophyll molecule, fossil essay, may fossil essay used as proof of photosynthesis. Sometimes, indications of prior existence of organisms in the sediments of earth may be regarded as trace fossils or Ichnofossils. These include animal tracks or foot print preserved in rocks, burrows of invertebrates, coprolites fossil excretesgastroliths polished stones in the abdomen of dinosaursfossil essay, gnawed bones, etc.
Microscopic organisms like bacteria, spores and pollen fossil essay, fungal and algal spores, foraminifera, diatoms, epidermal and wood fragments of plants etc.
preserved in the sedimentary deposits are referred to as microfossils. Microfossils are visible only after maceration of sediments. Large parts of plants like leaf, stem, root, flower, seed, etc, fossil essay.
and animal remains as whole organism or in parts, preserved in the sedimentary deposits are called megafossils. These are visible to naked eyes and are the better source of fossil essay as well as anatomical studies. The megafossils may be categorised into the following five types on the basis of the nature of fossilisation:. These are plant parts, compressed by the vertical pressure of the sediments Fig.
The plant fragments like leaves, fossil essay, stem, seeds get flattened and are retained as thin carbonaceous films with outline of external features. Generally, internal structure is not preserved, however, in rare instances cuticles, stomate, etc. are retained. Impression may be defined as the negative of a compression. These are just impression of plant parts which do not contain organic matters as in compression Fig. The sediments containing fossil essay flattened plant parts become hardened and when split open shows the negative imprint i.
These are the best, but rarest types of fossil which preserve the external form as well as the internal structures. The cellular details are preserved due to the infiltration of minerals like SiO 2CaCO fossil essayMgCO 3FeS, etc.
into the tissue. The petrified fossils can be cut into small pieces and series of section can be made for anatomical studies Fig. In these types, the deposition of iron and carbonate minerals occurs in the form of a hard cast around the plant parts.
The internal structure is degraded to form a cavity which is completely filled up by the surrounding sediments. Thus, the external preserved surface of the plant part is called a mold Fig. Stigmarian root system is an example of mold, while the pith cast of fossil essay Catamites stem is a common example of incrustation Fig, fossil essay. In these types, only external forms are preserved, while internal cellular details are not preserved.
A certain time period is required for the formation of a fossil. If the plant or animal parts are excavated before they completed their fossilisation process, they are called sub-fossils. Coal is a compressed fossil, while peat, an early stage of coalification is referred to as sub-fossil. Sometimes inorganic rocks that appear to be fossils are actually mineral deposition, fossil essay.
These fake structures are mistaken for plant or animal remains. These are known as pseudofossils. The fossilised organisms that held in a stratum younger or older than the fossil themselves are called derived fossils. These are results fossil essay tectonic movement of earth or other geological upheaval.
The fossil essay spherical balls containing plant parts are commonly termed coal balls Fig. These spherical balls are formed as a result of infiltration of plant debris in swamps by carbonates of calcium or magnesium, thus restricting the conversion of the debris into coal.
Coal balls occur in localised regions and they range in few centimeters to several meters and weigh from a few to several pounds. Coal balls are specifically significant in palaeobotanical studies. It consists of thin dead leaves, dispersed in organic matrix. The inner tissues of leaves are destroyed, thus the paper coal consists of layer after layer of cuticles, often with decomposed stems. The carbonaceous lime stone horizon at Tovarkovo, in Toula in Russia, fossil essay an example of paper coal.
The fossilised resin of extinct coniferous trees, Pinus succinifera in particular, fossil essay, is called Amber. The resinous exude flowed due to injury caused by boring insects which eventually accumulated on the forest floor and got hardened forming amber. Insects and flowers are often found preserved in amber. Amber has high economic value and used in jewelllery. The organisms that help in dating other fossils found in the same sedimentary layer are called index fossils, fossil essay.
Such fossils are found widely distributed geographically, and limited in time span having very distinct characteristic features. Monograptus is an index fossil of Lower Devonian, while Myrepollenites is fossil essay marker of Eocene.
Foraminifera, pollen grains, fossil essay, spores etc. are also used as index fossils. Essay 3. Nomenclature of Fossils : The fossil essay plant is not preserved, but only detached fossil essay parts like stem, root, cone, leaf, etc. are preserved as fossils. These detached plant parts are being discovered in different times by different authors. Thus, these detached plant parts or organs are given a bionomial generic and specific name by the same set of rules under the International Rules of Botanical Nomenclature which have been framed for living plants.
The first valid description of Lepidodendron came into existence from the publication of Sternberg in Each detached organs or fragments is given a different name. Each of these names acquires the status of a genus.
The generic name in fossils is applicable for only a plant part like root, stem, leaf, cone or other organ, without indicating to what plant it belongs. Thus, the genus is termed form genus or artificial genus in contrast to natural genus for living plants.
A form genus cannot reliably be assigned to a single family, however, it may be assigned to an order or other higher taxonomic rank, fossil essay. For example, fossil essay, Stigmaria is a form genus of the order Lepidodendrales which cannot be assigned to any one of the three families: Lepidodendraceae, Sigillariaceae or Bothrodendraceae, fossil essay. When the relationships among different organs like stem, root, leaf and reproductive structures are established and can be assigned to fossil essay same family, then the genera can be called organ genera, fossil essay.
For example, stem genus Bucklandia, leaf genus Ptilophyllum, male fructification Weltrichia and female fructification Williamsonia are genetically related and assigned to the same family Williamsoniaceae. Thus, all are considered to be organ genera. However, there is no provision in the International Rules of Botanical Nomenclature for the use of organ genera, fossil essay.
During reconstruction, the palaeobotanists should select the earliest after validly published generic name applied to any one of its parts as per Rule of Priority, fossil essay. He or she will use any one of the form genera as the generic name for the whole organism. Say, for example, the validly published female fructification, Williamsonia has fossil essay used for naming the whole plant. Essay 4. Techniques for the Study of Fossils: The following points highlight the top four techniques used for the study of fossils.
The techniques are: 1. Ground Thin Section 2. Film or Peel Technique 3. Transfer Technique 4. Maceration Technique. The smooth surface is attached to a glass slide with melted resin. Then, fossil essay, the specimen is cut as close to the glass as possible, thus a moderately thin section is obtained, fossil essay.
The thin section fixed to the glass slide is further ground on a revolving lap with carborundum till sufficiently translucent, so that the section can be viewed under the microscope. Finally, the slice is mounted with a cover glass using suitable mounting media.
A thin section of petrified wood can be made that preserves the cellular structure in an unchanged condition. b A small number of sections can be made from a given specimen, thus a lot of material is wasted. This is a conventional and most suitable technique for study of well-preserved petrifactions with considerable organic materials. The etched surface is gently washed in running water for the removal of acid and is air-dried and then covered with a solution or a thin film of nitrocellulose.
The specimen is air-dried for at least 6 hours. Then the film is carefully peeled by loosening one edge fossil essay is permanently mounted on a slide with a cover- glass using suitable mounting media.
An improvement fossil essay the peel technique has been made that makes possible rapid preparation of serial sections. This technique is most suitable for study of coalified compression which reveals additional details of venation, epidermal pattern and hairs.
The face of the specimen adjoining the rock surface is cleaned either mechanically or by washing in an acid for removal fossil essay rock particles.
The prepared surface of the rock is coated with a solution of nitrocellulose or with a cellulose acetate film.
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Fossil Tiktasalik Essay Words 3 Pages The author and his colleagues chose to focus on million year old rocks in their search for fossils because amphibians that look dissimilar to fish were discovered in million year old rocks, while fish without amphibian characteristics were discovered in million year old rocks View Fossil Findings blogger.com from ANTH at University of Texas, Rio Grande Valley. 1 ANTH Fossil Findings When looking back into Page 1 of 50 - About essays Body Fossils and Trace Fossils Fossils can be divided into two categories, body fossils and trace fossils. Body fossils encompass preserved remains of an organism, such as bones, claws, teeth, skin, embryos,
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