Search results
Results from the WOW.Com Content Network
For example, the pentadactyl limb bone structure observed in the arms of primates, front legs of equestrians, in the wings of bats, and the flippers of seals. The fact that they are homologous is further evidence for phylogenetic inertia; these structures have been modified over time, but they are constrained by common ancestry.
A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
Biological constraints are factors which make populations resistant to evolutionary change. One proposed definition of constraint is "A property of a trait that, although possibly adaptive in the environment in which it originally evolved, acts to place limits on the production of new phenotypic variants."
The larval form is not capable of feeding, though it may have a rudimentary digestive system, [53] and is only a dispersal mechanism. Many physical changes occur to the tunicate's body during metamorphosis , one of the most significant being the reduction of the cerebral ganglion, which controls movement and is the equivalent of the vertebrate ...
Thus, if the first four cells are separated, each can develop into a complete small larva; and if a cell is removed from the blastula, the other cells will compensate. This is the source of identical twins. The mesoderm forms as evaginations of the developed gut that pinch off to form the coelom. This process is called enterocoely.
A phylogenetic tree, phylogeny or evolutionary tree is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time. [ 1 ] [ 2 ] In other words, it is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon ...
In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, and synapomorphy all mean a trait shared between species because they share an ancestral species. [a]
The phylogeny of the teleosts has been subject to long debate, without consensus on either their phylogeny or the timing of the emergence of the major groups before the application of modern DNA-based cladistic analysis. Near et al. (2012) explored the phylogeny and divergence times of every major lineage, analysing the DNA sequences of 9 ...