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