Midterm #1 Flashcards
Epibenthic
: Living on or just above the substrate
Infaunal
Living within the substrate
Pelagic
Organisms live within the water column
Apomorphy
any derived or specialized character
Autoapomorphy
a derived character possessed by only one descendant of an ancestor, and thus of no use in discerning relationships among other descendants
Cladogenesis
the splitting of a single lineage into two or more distinct lineages
Homoplasy
the independent acquisition of similar characteristics (character states) from different ancestors through convergence or parallelism. Such homoplastic events create the illusion of homology.
Paraphyletic Grouping
a group of species sharing an immediate ancestor but not including all descendants of that ancestor.
Pleisiomorphy
any ancestral or primitive character
Polarity
The direction of evolutionary change
Polyphyletic Grouping
an incorrect grouping containing species that descended from two or more different ancestors. Members of polyphyletic groups do not all share the same immediate ancestor. Members of polyphyletic groups may resemble each other because of the independent evolution of similar traits by different ancestors
Saturation
a situation in which the gene sequences being compared have experienced so many base-pair substitutions hat the phylogenetic signal is largely lost.
Synapomorphy
a derived character that is shared by the most recent common ancestor and by two or more descendants of that ancestor. In cladistic methodology, synapomorphies define clades; that is, they determine which species (or other groups) are most closely related to each other. Essentially, synapomorphies are homologous characters that define clades.
Cladistics
Cladistics is an approach to biological classification in which organisms are categorized in groups based on hypotheses of most recent common ancestry
Phylogenetic Classification
is the evolutionary history of group of related organisms
Choanoderm
Internal cell layer of sponge. Made of choanocytes
Pinacoderm
External cell layer of sponge. Made up of pinacocytes
Mesohyl
Gelatinous middle (connective) layer in a sponge. Made of spicules, collagen and archaeocytes
Choanocyte
Flagellated collar cell responsible for current and food capture
Archaeocytes
free ameboid cells; food digestion, nutrient storage, skeletal secretion and gamete differentiation
Spicules
Structural components of the sponge. Calcium or silica
Spongin
the modified type of collagen that forms the mortar to help hold together spicules
Choanoflagellates
the clade of unicellular heterotrophs
Asconoid
Basic body plan, atrium with a single osculum
Syconoid
Infolding of the atrium to form radial canals. More complex with increased SA
Leuconoid
Highly complex body plan, with many, flagellated chambers and often many oscula
Class Calcarea
calcareous spicules and all 3 body plans
Class Demospongiae
Siliceous spicules and/or spongin. Leuconoid and most sponges belong to this class
Class Hexactinellida
Siliceous spicules (6 point fusion) and syncytial tissue
Syncytial Tissue
Multinucleate cell with cytoplasmic mass confined within one cell membrane
Gemmules
a tough-coated cluster of dormant embryonic cells produced by freshwater sponge. Wait for favourable conditions then develop (asexual)
Cnidaria Major Characteristics (6)
True Gut (carnivores) Diploblastic Radial Symmetry Nerve Net Cnidocytes – synthesize cnidae Alternation of generations: polyp and medusa
