Definitions Flashcards
etymology
study of word origin
taxonomy
the practice of classifying organisms
ie. naming and classifying organisms
systematics
theory of classifying organisms
ie. theory behind why we put organisms in their classification
nomenclature
system of rules for naming things
taxonomic ranks
drawers that jars (taxa) are placed in
taxon/taxa
groups that have been given names
extant
still alive
extinct
no longer have any living members
type
official exemplar of a new species
holotype
specimen of the new species placed in insect collection
phylogenetic tree
ancestor-descendant relationship portrayed in a tree like format
cladistics
system we use to place organisms in a phylogenetic tree
dichotomously branching pattern
when a branch splits into two
synapomorphies
shared derived features
ingroup
taxa whose relationship you want to untangle
outgroup
taxa known to have split off prior to diversification of the taxa of interest
nodes
points of species diversification
clade
group that contains descendants of a common ancestor
taxon
when a clade is named it is called a taxon
synapomorphies
derived traits present in more than one ingroup taxon
symplesiomorphies
shared ancestral traits
autapomorphies
derived traits present in only one taxon
homologous
character states that are present in more than on species and that arose once
homoplasious
states that are present in more than one species and arose independently more than once (convergent or parallel evolution)
reversals
type of homoplasy but there is a reversal from a derived to an ancestral state
convergence
when two or more lineages evolve independently toward a similar stare
divergence
two or more lineages evolve independently to become less similar
radiations
multiple divergences from a common ancestor result in more than two descendant lineages
parallel
two or more species of closely related taxa achieve similar evolution modifications
homology
similarity due to shared ancestry between a pair of structure or genes in different taxa
homoplasy
similarity in form or function between parts of different species or lineages that is not attributable to common ancestry but is the result especially of parallel or convergent evolution in similar environments
parsimonious
simplest explanation is the most plausible explanation
sister taxa
share a common ancestor
consesus tree
a tree that combines many parsimonious trees with agreements as resolved dichotomous branches and disagreements as polytomies
polytomies
branching into more than two, we do not know set of relationships
monophyletic taxa
those that contain all descendants of a common ancestor and no other
paraphyletic
taxa missing one or more descendants
polyphyletic
taxa include species that do not share a most recent common ancestor
unicellular
single celled (almost all protists)
multicellular
more than one cell (all plants and animals except as zygotes)
5 criteria
- is not viable as a single cell (except as a zygote)
- cells are interdependent
- cells are morphologically differentiated for different tasks
- 2 or more cells work in coordinated fashion on common task
- 2 or more layers of cells are present in the organisms body
cilia (short beat stiffly) and flagella (long and beat is undulating)
cell organelles whose beating can move fluid through the body of an animal or ins some cases move an animal through fluid
-almost all animals have at least some ciliated or flagellated somatic cells (exception Arthropoda)
symmetrical
split into relatively similar halves
plane of symmetry
a symmetrical body has an axis down the middle called the plane of symmetry
asymmetrical
lack any plane of symmetry
spherical symmetry
completely spherical in shape and have infinite planes of symmetry (virtually no examples in nature only a few protists but they are not truly spherical)
radial symmetry
body parts are arranged radially around a central oral-aboral axis common in polyps like a anemone
biradical symmetry
occurs when there is an oral-aboral axis but differentiation means there is only two planes of symmetry like a jellyfish with two tentacle’s
quadriradial symmetry
oral aboral axis but differentiation makes it have 4 planes of symmetry like box jellie
pentaradial symmetry
oral aboral axis and in this case 5 planes of symmetry like a starfish
bilateral symmetry
a single anterior posterior plane divides the body into two mirror images like a lobster
mitotic binary fission
one cell duplicates into two (in protists but not metazoans)
fragmentation
one body is split into many (sponges and many worms have this)
budding
a individual grows a second self on themselves (can split off and become its own being or stay attached)
isolecithal eggs
yolk particles distributed evenly through the cytoplasm
telolecithal eggs
yolk concentrated toward one end of the egg
centrolecithal
eggs have yolk concentrated at the center of the cell
simultaneous hermaphroditism
organisms are both male and female at the same time
sequential hermaphroditism
at separate times in the animals life they are female or male
parthenogenesis
females can produce eggs that develop into offspring without being fertilized
- unfertilized eggs= males
- fertilized eggs= females
cleavage
initial cell divisions
holoblastic cleavage
complete seperation of the blastomeres and occurs in isolecithal and lightly telolecithal eggs
meroblastic cleavage
incomplete seperation of blastomeres and occurs in strongly telolecithal eggs because cell membranes can’t penetrate the dense yolk
radial cleavage
early cell divisions after the 4-cell stage stack new blastomeres directly above the previous ones
spiral cleavage
the new row of blastomeres is twisted slightly off center
blastula
after few cleavages have produced numerous cells but before formation of the germ layers embryo is called a blastula
coeloblastula
holoblastic cleavage usually results in a hallow ball of cells a coeloblastula
discoblastula
meroblastic cleavage results in a cap of cells lying on trop tf the yolk this is dicoblastula
