L2 Invertebrate Organization Flashcards
Monophyletic
Classification when a group of organisms all share the same common ancestor and every descendant of that common ancestor is included.
Paraphyletic
Classification when a group of organisms share the same common ancestor but not every descendant of that common ancestor is included.
Polyphyletic
Classification when a group of organisms have more than one common ancestor.
Homologous traits
Character states, traits that were derived through evolution and divergence (common ancestry). PHYLOGENETIC RELATIONSHIP.
Analogous traits
Character states or traits among organisms that were derived out of necessity or because of exposure to similar environmental conditions (selective pressures). NO EVOLUTIONARY RELATIONSHIP = CONVERGENT EVOLUTION
Simplesiomorphies
Homologous traits that all organisms in a group share. So they cannot be used to describe relationships in the group because there is no divergence.
Cladistics (Systematics)
Grouping organisms and finding the phylogenetic relationships between mono phyletic groups of organisms. BASED ON THE MOLECULAR LEVEL NOT PHENOTYPE.
Synapomorphies
Derived character traits shared by members of a group. These types of traits can help us describe relationships because they are specific to some members in a group.
Asymmetry
No symmetry. No central axis or point arrangement of body parts. SPONGES
Radial symmetry
The arrangement of body parts such that a single plane cutting along the oral-aboral axis divides into mirror images CTENOPHORANS
Bilateral symmetry
The arrangement of body parts such that cutting a plane down the longitudinal axis will divide into equal right and left parts. HUMANS
Diploblastic
Ectoderm –> epidermis
endoderm –> gastrodermis
Middle layer of jelly-like filled mesoglea
Triploblastic
Ectoderm –> epidermis
Endoderm –> gastrodermis
Mesoderm –> support cells, contractile cells and blood cells
Body cavity
Triploblastic organisms are split up into DO THEY HAVE A BODY CAVITY OR NOT. Body cavities are fluid filled spaces where there’s lotsa room for organs to float around and to be separated from the body wall.
Why have a body cavity?
1) room for organ development
2) more SA for gas diffusion, nutrient diffusion and waste diffusion in and out of organs
3) storage area
4) act like a hydrostatic skeleton (think water ballon has more range of movement and flexibility)
5) give a way to eliminate wastes and reproductive products (babies)
6) allow for bigger body size
