Comparative Anatomy

Studies in Vertebrate Structure

• Introductory Concepts • Evolution • Kinds of Chordates • Developmental Processes

• What should we know about anatomy – Parts – Names – Developmental Origins – Functions

• Introductory Concepts • Evolution • Kinds of Chordates • Developmental Processes

• Comparative - why comparative?

– Logical progression, learn in steps – Comprehensive, know all vertebrates easily – Broadens our frame of biological knowledge •Phylogeny •Evolution •Embryology •Physiological ecology

• What is a chordate?

– In respect to other animals – 3 germ layers (not a sponge) – Bilateral symmetry (not a cnidarian) – Tube gut (not a flatworm) – Eucoelomate (not a round worm) – Deuterostome (not mollusk, annelid, or arthropod) – Segmented (not an echinoderm) – Unique features of chordates – Pharyngeal gill slits – Notochord – dorsal nerve chord

– What are the chordate subphyla?

• Urochordata -

tunicates

• Cephalochordata –

amphioxus

• Craniata (formerly vertebrata) » » » » » » » »

Hagfish Lamprey Cartilagenous fish Bony fish Amphibians Reptiles Birds mammals

• Phylogeny – “family tree” of taxa • Ontogeny - developmental process • Von Baer’s Law – “features common to all members of major phylogenetic group of animals develop earlier in ontogeny than do features that distinguish subdivisions of the group” – (shared features develop earlier)

• Conserved traits – shared by all or most subgroups of a taxon and assumed to be passed down from one ancestral line • Derived traits – present within a subgroup of a taxon as a new trait which differentiates that subgroup from others.

• The hierarchial system of taxonomy – Kingdom – Phylum – Class – Order – Family – Genus – Species

• Problems with the hierarchial system – Discrete levels oversimplify the phylogeny – Arbitrary placement of taxonomic levels – Backward jumps in taxonomic level names – Standards for classification are not the same in all groups

• Problems with the species concept

– Discerning the viability of hybrids – Populations mix in some areas, but not others – Ring species – Checking for reproductive separation of allopatrics – Clones and parthenogens – Polyploid species

• Lumpers and Splitters

•EVOLUTION

a controversial subject – Diversity of viewpoints •Literal Genesis, deny evolution •Literal Genesis, accept natural selection •Figurative Genesis, God directs evolution •Figurative Genesis, God initiated universe •Deny God as a factor in the natural world

• Levels of scientific certainty Hypothesis --------------------------------> Law Theory Law – supported by all experimentation, and all alternatives disproven by experimentation

• Five tiers of evolutionary concept – Development of first life form – Microevolution – Natural Selection – Speciation – Macroevolution

• Development of first life form – Cooling of Earth allows molecule formation and development of an atmosphere with methane, water, ammonia, hydrogen, and nitrogen – Further condensation forms organic molecules – Accumulation of organic “soup” – Organic macromolecules (preorganelles) – First reproducing cell

• Microevolution – Replication and cell division errors result in genetic variants in a population – Not all members of a population will have the same genomes

• Natural Selection (survival of the fittest) – Because not all members of a population have the same genetic make up, some may have a survival advantage.

– Evidences •Peppered moth •Pesticide resistance •Galapagos finches

• Speciation – the isolation of a reproducing lineage from other lineages within the taxon • The allopatric speciation concept – Geographic separation – Genetic change – Reproductive isolation • Sympatric speciation