Key terms Flashcards
Taxonomy
science of naming and classifying organisms within Taxa
Phylogeny
The evolutionary history of a species
Systematics
the science of determining evolutionary relationships between organisms
Taxon
A unit of classification
Primitive characteristics
a character that belongs to all members of a group, but also members of the group before it
Parsimony principle
a phylogenetic tree is only a hypothesis, we first investigate the hypothesis with the fewest evolutionary steps of DNA base changes
asymmetry
No symmetry
Such as in Porifera
Radial symmetry
Symmetry is circular, there is no left or right side
such as in adult Echinoderms and Cnidarians
Bilateral symmetry
The animal is symmetrical from left to right
Such as in Chordata, Arthropoda, Mollusca, Platyhelminthes, Annelida and Nematoda.
Coelom
The internal body cavity inside most animals that contains the organs, surrounded by mesoderm
Coelomate
Animal that has an internal cavity surrounded by mesoderm
acoelomate
animal does not have an enclosed body cavity
pseudocoelomate
animal has a cavity but it is not entirely surrounded by mesoderm, partly surrounded by endoderm
pseudocoelomate
animal has a cavity but it is not entirely surrounded by mesoderm, partly surrounded by endoderm
explain the development of a protosome
in 8 cell stage, the two layers are offset, the solid masses of the mesoderm tissue split to form the coelom, the mouth develops from the blastopore
