There's+Evidence+for+Evolution?

//**__Evolution__**// is the term used to describe a genetic change or a change in allele frequencies from generation to generation. Microevolution is a change in one gene pool of a population over successive generations. Macroevolution refers to continuous evolution over many generations leading to speciation. But any failure to evolve properly due to environmental changes might result in extinction of the species. There is a vast amount of evidence found that confirms that occurrence of evolution. __//**Evolutionary hypotheses are currently being tested to prove the concept of evolution while some other factors like fossil record, comparative anatomy, comparative embryology, molecular biology, natural selection and biogeography are creating stronger evidence of the occurrence of this complex phenomenon of evolution.**//__

__//**A. What's hidden in the fossil record?**//__ Fossil record is the most direct evidence of evolution that comes from the direct study and interpretations of fossils. The process of fossilization occurs very rarely and, before the process begins, the animals or plants must be decayed or scavenged. Remains of the plants and animals that are found in sedimentary rock layers show us a record of changes through time and gives us a better idea about the variety of living things that have existed in the past. Some extinct species even contained traits that were transitional between major groups of organisms. Some fossil records are not available to the scientists as they occur in rocks while some are available but being destroyed by weathering and erosion before being collected. The gaps in the fossil records that are due to the inability of collecting information are filled with transitional fossil specimens. As a result, only a few species that have existed are known from their fossil records. Nevertheless, the fossils that are available are sufficient enough to prove evolution over generations. The fossil record shows a progression from the unicellular organisms to today’s most complex multi-cellular organisms. Even though most fossil remains are found in sedimentary rocks, recent findings have been well preserved in bogs, tar, amber or ice.



Various methods are being used to determine the age of fossils in order to figure out the chronological order of the time period when the species existed. Since layers of sedimentary rock layers are based on the sequence of their deposition, most fossils are dated according to their position in the sedimentary rocks. Index fossils are fossils that existed for a short period of time but were preserved in large numbers, which helps geologists in arranging the rock layers in chronological order and identifying the comparable layers in various locations. Studies of radioactive dating and half life also help in determining the age of fossils as each radioisotope has its own characteristics of decay. According to these studies, prokaryotes are the first organisms developed on earth which is 4.6 billion yeas old and paleontologists discovered many transitional forms that help link older fossils to modern species proving that evolution is occurring. For example, //Eohippus// links to the modern horse, while //Archaeopteryx// links reptiles and birds. Imagine, that tranquil pigeon you saw on the street is related to one of the most aggressive types of early organisms!

Comparative Anatomy is the study of different structures that contributes to a better understanding of the anatomical structures Living things on earth are very similar to each other while it comes to the basic way of living. No matter whether or not it’s a simple unicellular organism or a multi-cellular complex organism, they all start out with the same single celled organisms with the similar reproductive processes. The species that have a common origin and reflect a common ancestry is known as homologous structures. Human arms, cat forelimbs, whale flippers, and bat wings contain very similar structures as they are derived from same common ancestors supporting the facts of evolution (see figure below). Leaves are a very good example of homology in plants. For different functions, leaves are seemed to be modified its structures in various ways, again supporting evolution. Homoplasy displays crucial evidence of evolution as well as they show a different ancestry but similar adaptations due to the same environmental conditions. For example, the wings of insects and birds are not closely related but evolved to meet the same need for flight as a result of evolution. Comparative anatomy also shows us the existence of structures that are no longer able to function or vestiges. The vestigial structures may have a better usage among the ancestors but due to the new environmental condition, they may have no usage at all. An great example would be your appendix! These structures become vestiges as a species gradually lose their needs for survival.
 * //__B. Are there similarities found between body parts of living organisms?__//**



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