The second organism is a species of bird. Again using the dichotomous key, we find that this organism has a regular body shape. The bird has bilateral symmetry with an internal skeleton. The bird’s appendages are jointed, not fin-like. The body of the bird is not covered in scales, the skin is covered with feathers and claws are present. 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. This organism therefore falls into the class Chondrichthyes.
The fifth organism has a regular body shape with bilateral symmetry and an internal skeleton. This animal’s appendages are jointed, not fin-like. There are no scales on the body of this animal and the skin is covered with hair. Using this information and the dichotomous key we determine that this animal should be classified in the class Mammals.
The sixth organism has a regular body shape with bilateral symmetry and has no apparent skeleton. It has a hard outer covering and has jointed legs which are only on certain body sections, and not all appendages are legs. This organism does not have claws. It has four pairs of legs and no wings or antennae. 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.a Class Reptilia
References
Audesirk, T., Audesirk, G. & Byers, B. Biology: Life on Earth. New York: Prentice Hall,
2001.
Audesirk et al., Biology: Life on Earth (New York, Prentice Hall, 2001) 146-151.
