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Assignment 5: Dichotomous key

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Introduction

Assignment 5: Dichotomous key Prior to evolutionary theory, scientists relied on similarity of physical characteristics to classify organisms. An 18th century naturalist, Carolus Linneas, developed a taxonomic classification system. This hierarchical system divides organisms into 5 kingdoms. Organisms visible to the unaided human eye fall into the plant, animal, or fungi kingdom. Kingdoms are then divided into phylum. This division is based body type and skeletal organization. Phylum are then divided into subphylum. Subphylum are divided into classes, orders, genus, and then species. This system of classification is still used by scientists today1. In this assignment, seven organisms are presented which are to be classified into phylum or class based on a dichotomous key. ...read more.

Middle

Using these physical characteristics we find that this organism falls into the class Aves The third organism appears to be a type of shark. The shark has a regular body shape with bilateral symmetry and an internal skeleton. The body of this animal is not fish-like and appendages are jointed. The body is not covered by scales and claws are absent. Therefore, this organism falls into the class Amphibian. The fourth organism has a regular body shape with bilateral symmetry and an internal skeleton. The organism has a fish-like body with fin-like appendages. The scales on the body of this creature do not overlap and its skeleton is made of cartilage. ...read more.

Conclusion

Given these physical characteristics, we can use the dichotomous key to determine that this organism falls into the class Arachnida. The seventh organism has a regular body shape with bilateral symmetry and an internal skeleton. The animal's appendages are jointed, not fin-like. The body is covered by scales and the animal has four legs. The organism therefore falls into the class Reptilia. Key Organism 1 1.b, 2.a, 4.a, 18.a Class Asteroidea Organism 2- 1.b, 2.b., 3.a, 19. b, 21. b, 22.b, 23. a Class Aves Organism 3 1.b, 2.b., 3.a, 19. b, 21.b, 22.a Class Amphibia Organism 4 1.b, 2.b, 3.a, 19. a, 20.a Class Chondrichthyes Organism 5 1.b, 2b., 3a., 19.b, 21. b, 22.b, 23.b Class Mammals Organism 6 1.b, 2.b, 3b., 6.a, 10a, 14.b, 16.b, 17.a Class Arachnida Organism 7 1.b, 2.b, 3.a, 19. b, 21. ...read more.

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