Macroevolution –The result of repeated speciation events –Evidences From Comparative Anatomy From the Fossil Record From Biochemistry From Biogeography

Macroevolution evidences from the field of comparative anatomy –Congruence of anatomical features –Vestigial structures –Homology –Living intermediates –Von Baer’s Law

Congruence of anatomical features –Shared features of 2 species which are derived from common ancestry should be numerous. –If two species are not from a shared ancestry then there is no particular reason for them to share an abundance of anatomical features.

Vestigial Structures Anatomical features which serve no function, or are more of a liability than a help. Thought to be passed down from an ancestor in which the feature served a beneficial purpose. Examples – whale hipbones, eyes of blind cavefish, ear moving muscles of humans

Homologous Structures Anatomical features which have the same developmental origin, but have a variety of developmental outcomes. Example – The limb bud of the vertebrate becomes bird wing, bat wing, whale flipper, horse leg, and human arm.

Living intermediates Any species or taxon which has anatomical features that are considered similar to an ancestral group linking two dissimilar taxa. Examples – Hemichordates have features linking echinoderms and chordates. Peripatus has features linking annelids and arthropods.

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

Evidences for macroevolution from the field of paleontology –Confirmation of fossil age Strata sequence Isotope dating Index fossils –Missing links

Concept of superposition

Fossil Succession

Volcanic events and dating rocks

Index fossils – rock beds with similar fossils are assumed to be approximately from the same age. If the age of one bed is known the matching beds are assigned the same age until proven otherwise.

Missing links are extinct forms that share features from two separate phylogenetic lines.

Evidences for macroevolution from the field of biochemistry –Proteins immunotaxonomy electrophoresis amino acid sequence –DNA DNA – DNA hybridization nucleic acid sequence

Evidence for macroevolution from the field of biogeography –Continental drift and phylogenetic lines –Taxa and their geographic radiations –Islands, refugia and speciation

Continental Separations –Pangea (triassic,220my) –Laurasia – Gondwana (jurassic, 160my) –N. America, Europe, Asia, S. America, Antarctica, Australia, Africa, India (cretaceaous, 100my) New Land Bridges – Berringea, DeGeer/Thule passages, panamanian connection, Middle Eastern

Radiation of Taxa –Regions of endemism may show a greater variety of taxon subgroups via repeated speciation events. –Regions more distant from an endemic center often have fewer taxon subgroups present.

Islands, refugia and speciation –Fragmented populations, located in refugia of suitable habitat or on islands, speciate and form recognizable subgroups.