Biological Classification

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Table of Contents

INTRODUCTION.......................................................................1

PART A .....................................................................................1

PART B.....................................................................................2

PART C.....................................................................................3

REFERENCES............................................................................5

DIVERSITY OF LIFE

INTRODUCTION:

[pic 5]The “Biological Classification” is the grouping of organisms by the similar features they share among them. (Biological Classification, 1997) Taxonomy is another term that comes across when talking about classification which is described to be the science of naming and classifying accordingly. Comparing to the times of Aristotle and other scientists, the similarity was determined by investigating the physical characteristics but now, modern classification is used through a variety of techniques such as genetic analysis and DNA technologies. The worlds we live in today consist of a great diversity of life, ranging from simple to complex organisms. (Fig: 1) There are about 8.7 million species living on earth of which approx.6.5 million lives on land and remaining 2.2 million lives in the ocean. (Sweetlove, 2011)[pic 6]

PART A:[pic 7]

The use of classification has changed over the period time from what it used to be at the initial stage. The evolution of the system of classification started way back in the 4th century, when a Greek philosopher, Aristotle, commonly known as the ‘father of science’ classified living things as animals and plants(Westbroek, 2000).(Fig:1.1) and further classified them by structure and size for plants and based on where they live for animals. As time travelled, it was understood that Aristotle’s classification system was limited and no longer adequate as newer species were found, even though it lasted for about 2000 years. It was not until in the 17th century, John Ray- an English naturalist and botanist who made significant zoological contributions in the history of classification. (Westfall, 2014) He was one of the greatest predecessors who made Carolus Linnaeus’ contributions possible in the following century. In the 18th century, Carolus Linnaeus - Swedish botanist, physician and zoologist, assembled Ray’s work and finalised that there are two kingdoms for classifying living things - kingdom Animalia and kingdom Plantae. His system of classification has been developed the modern classification system used by all over the world. He named the system as “Linnaeus’ System of Classification” (Ucmp.berkeley.edu, 2000) which consisted of the two broad kingdoms (Animalia and Plantae) divided into Phylum, then subdivided into Class, to Order, to Family, to Genus and finally to Species.(Fig:1.3) Along with classification of species according to their structural similarities and also formalised a modern naming system for organisms called the ‘binomial nomenclature’ which means each organism has a two-part scientific name where the first part is Genus(a group of similar species) and the second part is species(unique to each species). [pic 8][pic 9]

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As new species were gathered of life’s enormous diversity, biologists argued that two kingdoms are not sufficient and through the invention of the microscope, it opened new ways to classify such as it revealed that fungi cannot be classified as plants because it does not photosynthesise. Therefore in 1866, a German naturalist Ernst Haeckel proposed the idea of the third kingdom which included the single - celled organisms known as Protista. (Scientists, 2016)Later, several biologists also argued about the domain systems and currently we have a system of three main domains which has been divided into Bacteria, Archaea and Eukaryota. The prokaryotes are separated into Eubacteria (Bacteria) and Archaebacteria (Archaea) as it has its unique features and thus why eukaryote is placed in the different domain because prokaryotes lack a membrane-bound nucleus and eukaryote has a membrane-bound nucleus. (Smith, 2005)An example of biological classification is given in Fig: 1.4 of Leopard.

PART B:[pic 11]

Over the time, the system of biological classification has become more important than ever. As newer species were found, biologists faced the duty of identifying and describing them. Therefore, they needed an orderly and logical system which is used for naming and describing organisms to show their past and present relationships. When newer species were found, scientists encountered a problem, to remember organisms’ names. (Sleem, 2016)In order to study the diversity of life, the most efficient way is to classify organism to their relative group. This helps us to examine the relationship between the species within the group they are assigned to. Scientists avoided language barriers by using Latin as the language to name organisms scientifically which was universally accepted. An example of identifying species is the dichotomous key which enables us to predict species of organisms through set number of characteristics ranging from common to specific. (Oregonstate.edu, 2012) Modern technologies such as phylogenic trees and cladograms (Fig: 1.5) are used by scientists to illustrate relationships between species and the evolutionary relationships with a common ancestor. However, there are differences between those, as the cladograms might have derived from a common ancestor and subdivided into different branches but on the other hand, phylogenetic trees are equivalent to the evolutionary timescale, therefore we can seek the how species have changed over time and can describe the relationship between ancestor and their descendants. (Enzor, 2013) When classifying organisms, mistakes could have happen, for example, there is a fish known as Pickerel in both Canada and USA; though only one is edible while the other is not because they both belong to different species, thus scientific name plays pivotal role in providing us with clear information and explanation on these issues. (Enzor -2, 2013)With the limited information on Aristotle’s classification, Linnaeus’ system of classification was widely adopted due to the hierarchal naming structure that conveyed complex relationship information about what species were and their close relatives. As the world is changing, scientists find new ways to classification such as through DNA analysis and genetic coding. The advancement in our understanding of organisms has lead to the change in classification systems we use today. As we discover more about species, the change in classification will further in pace with the improvement in technologies.[pic 12][pic 13][pic 14]