Explain the fluid mechanics principle known as a “Reynolds Number” and describe its relevance to the life of single cell protists like Paramecium.

3 ways in which a multicellular organism could evolve from a protist. Symbiotic Hypothesis 3 ways in which a multicellular organism could evolve from a protist. Colonial Hypothesis Cellularization Hypothesis

and the Theory of Recapitulation Ernst Haeckle (1834-1919) and the Theory of Recapitulation Haeckel promoted the influential (but no longer widely held) recapitulation theory ("ontogeny recapitulates phylogeny") claiming that an individual organism's biological development, or ontogeny, parallels its species' evolutionary history, or phylogeny. In what way does Haeckle’s colonial theory for the origin of animals reflect his believe in “recapitulation”?

Gastrea Blastea Gastrea Strengths: models exist (Volvox, choanoflag.) (Haeckle’s favorite) Gastrea Blastea Gastrea Strengths: models exist (Volvox, choanoflag.) : parallels animal embryology Weaknesses: ???

Blastea Gastrea Strengths: models exist (Volvox, choanoflag.) (Haeckle’s favorite) Blastea Gastrea Strengths: models exist (Volvox, choanoflag.) : parallels animal embryology Weaknesses: ???

Similarities of Choanocytes (sponge cells) and choanoflagellates (protozoan) Choanocyte Choanoflagellate

Choanoflagellates live as solitary and colonial forms

a. Phylogeny based on protein domain comparisons b-d. choanoflagellate cells bear a single Flagellum and an apical collar of actin-filled microvilli (bracket, c). D. an overlay of b-tubulin (reen), polymerized actin (red) and DNA (blue) localization reveals the position of the flagellum within the collar of microvilli.

Why present in a species that is unicellular? Monosiga genome: Encodes a diverse array of cell adhesion and extracellular protein domains previously thought to be restricted to metazoans. (cadherin required for cell sorting and adhesion during embryology (why in protist????) Lectins….cell recognition, adhesion Integrin and immunoglobulin…adhesive and immune functions Collagen domains: Key component of basement membrane in metazoan tissues Why present in a species that is unicellular?

Conclusions on Metazoan Origin Evidence best supports the colonial theory Choanoflagellate group is most likely ancestor; Evidence includes cell structure and genetic similarities Idea that metazoans are monophyletic is supported

Systematics, Classification and Phylogeny Accompanying textbook pages 19-31

II. Some Important Terms and Concepts Character Homologous Convergent states Polarity attributes or features of organisms similarity due to descent from a common ancestor similar-appearing structure evolved in entirely unrelated groups various conditions of homologous character ex. fins of fish, arms of humans, forelegs horses Direction of change...Ancestral and derived...is relative

Convergent vs. Homologous Ancestral vs. Derived Distinguishing characters by these criteria is key to learning about evolution and phylogeny. Why?

Key rules of cladistics taxonomy Only shared derived homologous characters determine phylogeny : synapomorphies All species in a grouping must share a recent common ancestor All species derived from a common ancestor as well as that ancestor must be included in the taxon All species must be in monophyletic taxa ( true reflection of evolutionary history)

Monophyletic Taxon? Polyphyletic Taxon: Paraphyletic Taxon: A taxonomic grouping of species that evolved from a single ancestor and includes all descendants of that ancestor Polyphyletic Taxon: An incorrect taxonomic grouping of species that arose from two or more recent ancestors Paraphyletic Taxon: An incorrect grouping of species sharing an immediate ancestor but not including all descendants of that ancestor.

Key rules of cladistics taxonomy All species in a grouping must share a common ancestor All species derived from a common ancestor as well as that ancestor must be included in the taxon Thus all species must be in monophyletic taxa all species in this taxon share a common ancestor and all species derived from that common ancestor are included Reptiliomorpha

Key rules of cladistics taxonomy All species in a grouping must share a common ancestor All species derived from a common ancestor as well as that ancestor must be included in the taxon Thus all species must be in monophyletic taxa This is polyphyletic as the Two lineages do not share A recent common ancestor

Key rules of cladistics taxonomy All species in a grouping must share a common ancestor All species derived from a common ancestor as well as that ancestor must be included in the taxon Thus all species must be in monophyletic taxa Grouping contains the immediate common ancestor but not all descendants of that ancestor are included

Ex. Vertebrate lineage Class Pisces? Class Reptilia? Orthodox classification of Vertebrate Animals.

Use the Linnean categories: PCOFGS Three important cladistics conventions in converting cladograms to taxonomic categories: Use the Linnean categories: PCOFGS Minimum taxonomic decisions will be made Minimize use of empty or redundant categorial ranks Division Ginglymodi Family Lepisosteidae Genus Atractosteus Genus Lepisosteus Ranks of well known clades will be retained 3. Asymmetric trees containing terminal taxa may be placed at the same hierarchal rank and listed in order of their branching sequence (Sequencing convention)

Ex. Vertebrate lineage Phylogenetics nested hierarchy Phylogenetics Sequencing convention Ph Chordata SubPh Vertebrata Class Pisces Class Amphibia Class Mammalia Class Anapsida Class Lepidosaura Class Crocodilia Class Aves Orthodox classification of Vertebrate Animals.