Word | definition |
systematics | a balanced arrangement of similar parts on either side of a common point or axis |
taxonomy | the description of species and the classification of organisms into groups that reflect evolutionary relationships |
nomenclature | the study of the naming of organisms in the fashio that reflects their evolutionary relationships |
taxon | a group of organisms that are genetically (evolunionarily) related |
domain | the broadest taxonomic grouping, recent evidence from molecular biology indicates that there are three domains; Archaea, Eubacteria, and Eukarya |
kingdom | the level of classsification above phylum, the traditional classification system includes five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia; recent evidence from molecular biology studies indicates that they may not be monophyleic lineages |
phylum | the level of clasification between kingdom and class, members are considered a monophyleic assemblage derived from a single ancestor |
class | A level of classification between phylum and order |
order | the level of classification between class and family |
family | the level of classification between order and genus |
genus | the level of classification between species and family |
species | a group of populations in which genes are actually, or potentially, exchanged through multiple generations, numerous problems with this definition make it difficult to apply in all circumstances |
monera | bacteria and the cyanobacteria, they are distinguished form other organisms by being prokaryotic |
protista | are eukaryotic and consist of single cells or colonies of cells, includes Amoeba, Paramecium, and many others |
Plantae | are eukaryotic, multicellular, and photosynthetic |
fungi | are also eukaryotic and mulitcellular, the also have cell walls and are usually nonmotile |
animalia | are eukaryotic and mulitcellular, and they usually feed by ingesting other organisms or parts of other organisms |
evolutionary conservation | the slowness of change in a characteristic of an animal over time, evolutinary conservation usually indicates that the characteristic is vital for normal funtions and that change is not tolerated |
Archaea | prokaryotic microbes that live in exstreme environments such as high-temperature rift valleys on the ocean floor, high-salt, or acidic environments |
Eubacteria | are true bacteria and are prokaryotic microorganisms |
Eukarya | domain that includes all eukaryotic organisms: protists, fungi, plants, and animals |
Monophyletic group | a group of organisms decended from a single ancestor |
character | an animal attribute that has a genetic basis and that can be measured, used by systematists in investigating relatedness among animal groups |
polyphyletic groups | an assemblage of organisms that includes multiple evolutionary lineages, polyphyletic assemblages usually reflect insufficient knowledge regarding the phylogeny of an group of organisms |
paraphyletic group | a group that includes some, but not all, members of a lineages, paraphyletic groups result from insufficient knowledge of the group |
evolutionary systematics | the oldest of the three approaches, the study of the classification of and the evoluntionary relationships among animals, the attempt to reconstruct evolutionary pathways based on resemblances between animals that result from common ancestry |
numerical taxonomy | a system of classification that does not attempt to distinguish true and false similarities |
phylogenetic systematices | or cladistics, the study of the phylogenetic relationships among organisms in which true and false similarities are differentiated |
symplesiomorphies | taxonomic characters that are common to all members of agroup of organisms, these characters indicate common ancestry but cannot be used to describe relationships within the group |
outgroup | in cladistic studies, is a group outside of a study group that shares an ancestral characteristic with the study group |
derived characters | character that has arisen since common ancestry withan outgroup |
synapomophies | characters that have arisen within a group since it diverged from a common ancestor, they indicate degrees of relatedness within a group, also called shared, derived characters |
clade | a subset of organisms in a phylogenetic group that share a certain synapomorphy (derived character) |
cladogram | diagram depicting the evolutionary history of taxa, derived from phylogenetic systematics (cladistics) |
symmetry | a balanced arrangement of similar parts on either side of a common point or axis |
asymmetry | without a balanced arrangement of similar parts on either side of a point or axis |
radial symmetry | a form of symmetry in which any plane passing through the oralaboral axis divides an organism into mirror images |
bilateral symmetry | a form of symmetry in which only the midsagittal plane divides an organism into mirror images, is characteristic of activiely moving organisms that have definite anterior (head) and posterior (tail) ends. |
cephalization | the develpoment of a head with an accumulation of nervous tissue into a brain. |
diploblastic | animals whose body parts are organized into layers that are derived embryologically from two tissue layers: ectoderm and endoderm; animals in the phyla Cnidaria and Ctenophora are diploblastic |
ectoderm | the outer embryological tissue layer, gives rise to skin epidermis and glands, also hair and nervous tissues in some animals |
endoderm | the innermost embryological tissue layer, gives rise to the inner lining of the gut tract, digestive gland, anf the inner lining of the respiratory system |
triploblastic | animals whose body parts are organized into layers that are derived embryologically from three tissue layers; ectoderm, mesoderm, and endoderm; platyhelminthers and all eoelomate animals are triploblastic |
mesoderm | the embryonic tissue that gives rise to tissues between the ectoderm and endoderm (e.g. muscle, skeletal tissues and excretroy structures.) |
acoelomate | without a body cavity |
pseudocoelom | a body cavity between the mesoderm and endoderm; a persistent blastocoel that is not lined with peritoneum, also callled pseudocoel. |
coelom | a fluid-filled body cavity lined by mesoderm |
comparative embryology | the study of animal development in an attempt to deduce evolutionary pathways in particular animal groups |
protostomes | animal in which the embryonic blastopore becomes the mouth, often possesses a trochophore larva, schizocoelous coelom formation, and spiral embryonic cleavage |
trochophore larva | a larval stage characteristic of many molluscs, annelids, and some other protostomate animals |
deuterostomes | animals in which the anus forms from, or in the region of, the blastopore, often characteriszed by enterocoelous coelom formation, radical cleavage, and the presence of a dipleurula-like larval stagedeuterostomes |