Taxonomy and Phylogeny of Animals CHAPTER 10 Taxonomy and Phylogeny of Animals

More than 1.5 million species of animals are named Linnaeus and Taxonomy More than 1.5 million species of animals are named Estimated that these account for Less than 20% of all animals currently alive Less than 1% of extinct animals Taxonomy (aka - Systematics) Formal system for naming and classifying species Science of classifying organisms based on similarity, biogeography, etc.

Systematics 3 types of Systematics/Taxonomy Evolutionary Systematics Grouping organisms that resemble ancestors Numerical Taxonomy Used mathematical models to group organisms according to overall similarities Phylogenetic Systematics (cladistics) Use “outgroups”, differences between taxa to make a subset called a clade (Greek - branch) Most commonly used, measures variety of characteristics. *Discussed later*

Greek philosopher Aristotle first classified organisms (350 BC) Linnaeus and Taxonomy Greek philosopher Aristotle first classified organisms (350 BC) Carolus Linnaeus designed the current system of classification (1750) Swedish botanist with extensive experience classifying objects, especially flowers Used morphology (study of form and structure) to develop a classification system of animals and plants Divided animal kingdom into species and gave each a distinctive name Grouped species into genera, genera into orders, and orders into classes His classification scheme has been drastically altered, but the basic principle is still followed

Carolus Linnaeus

Linnaeus and Taxonomy Hierarchy of taxonomic ranks now includes 7 major groups Kingdom, phylum, class, order, family, genus, and species Now, the new level of Domain is also used. All animals are placed in Kingdom Animalia, or Domain Eukarya Taxa (Taxon) - Groups of animals that share a particular set of characteristics. Example: True Flies “Diptera” - single pair of wings Each rank can be subdivided into additional levels of taxa Superclass, suborder, etc.

Division of Life - Milestones

3 Domains - current proposal Based on ribosomal RNA sequences

Nomenclature: assignment of a distinctive name to each species Taxonomy Nomenclature: assignment of a distinctive name to each species A scientific name of an animal consists of two words (binomial nomenclature) First word is the genus and is capitalized Second is the species written in lower case Scientific name should be printed in italics or underlined if handwritten Homo sapiens

Taxonomy Some animals are subspecies, usually caused by Geographic locations. They are referred to as trinomials (3 names) All three terms are in italics Subspecies is also in lower case Ex. Ensantina eschscholtzii (salamander) has many subspecies. E.e. plantens, E.e. picta, E.e.croceater

Biological Species Concept Been refined and reworded several times A species is a reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature. Ability to successfully interbreed is central to the concept 10-14

Reproductive Community Species Biologists use certain criteria for identifying species Common Descent Reproductive Community Member of a species must form a reproductive community that excludes members of other species

Taxonomic Characters and Phylogenetic Reconstruction Cladogram Diagram illustrating hierarchy of clades (groups of animals with common ancestry) To construct a Phylogenetic tree Additional information concerning ancestors, duration of lineages, and amount of evolutionary change must be included (compared to cladogram)

A cladogram Amphioxus is the “outgroup” because it doesn’t share any of the defining characteristic with the other taxa. What characteristic separates Bass from Horses?

Taxonomic Characters and Phylogenetic Reconstruction Sources of Phylogenetic Information (What do we use to identify animals??) Comparative Morphology Examines shapes, sizes and development of organisms Skull bones, limb bones, scales, hair and feathers Living specimens and fossils are used

Taxonomic Characters and Phylogenetic Reconstruction Comparative Biochemistry Analyzes sequences of amino acids in proteins and nucleotides sequences in nucleic acids Recent studies show comparative biochemistry can be applied to fossils Comparative Cytology Examines variation in number, shape and size of chromosomes Used almost exclusively on living specimens

Phylogenetic Tree based On Cytology: Comparing base substitutions on Cyctochrome C (a respiratory protein). #’ s represent number of Mutations that occurred.

Animal Kingdom Patterns of Organization Symmetry Asymmetrical (no central body point/axis) ex. sponge Bilateral (if divided right/left sides are mirror image) ex. vertebrates Radial (any plane cut through organism makes mirror image) ex. Sea anemone Embryonic Tissue Layers: Diploblastic - 2 tissues (ectoderm and endoderm) Triploblastic - 3 tissue layers (also mesoderm) Zygote Cleavage Protostome - blastopore becomes mouth Deuterostome - blastopore becomes anus

Major Subdivisions of the Animal Kingdom Traditional groupings based on embryological and anatomical characters Branch (Parazoa): phylum Porifera, the sponges and phylum Placozoa Branch (Eumetazoa): all other phyla

Major Subdivisions of the Animal Kingdom Branch Eumetazoa Grade I (Radiata): phyla Cnidaria Grade II (Bilateria): all other phyla Division A (Protostomia): (subdivisions made by presence of coelom in embryo) Acoelomates: phyla Platyhelminthes, Pseudocoelomates: phyla Rotifera, Nematoda, Eucoelomates: phyla Mollusca, Annelida, Arthropoda, Tardigrada, Division B (Deuterostomia): phyla Echinodermata, Chordata

Major Subdivisions of the Animal Kingdom Recent molecular Phylogenetic studies have challenged traditional classification of Bilateria Grade II: Bilateria Division A: (Protostomia):(subdivisions made by molting/shedding) Lophotrochozoa (non-molting): phyla platyhelminthes, Rotifera, Mollusca, Annelida, Ecdysozoa (outer covering sheds or molts): phyla Nematoda, Arthropoda, Tardigrada, Division B (Deuterostomia): phyla Chordata, Echinodermata