Macroevolution Macroevolution The result of repeated speciation events

Macroevolution • Macroevolution – The result of repeated speciation events • Speciation: the formation of new and distinct species in the course of evolution. – Evidences • From Comparative Anatomy • From the Fossil Record • From Biochemistry • From Biogeography

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

Congruence of Anatomic Features • 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

Whale hipbones

Ear Moving Muscle 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.

Homologous Structures

Living Intermediates 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.

Echinoderms

Chordates

Hemichordates

Hemichordates • The most distinguishing characteristic of the Hemichordate s is a more primitive form of notochord, called a stomochord that contained a nerve system.

Peripatus Onychophorans were once seen as the missing link between annelids (segmented worms) and arthropods (insects, spiders, crustacea). Like the annelids, they have a hydrostatic 'skeleton' – a fluid-filled core surrounded by muscle – instead of a hard exoskeleton like arthropods or a bony skeleton like vertebrates.

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 • Things in common appear first and then things that are different appear

Von Baer’s Law

Paleontology • 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.

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

Biogeography • Evidence for macroevolution from the field of biogeography – Continental drift and phylogenetic lines – Taxa and their geographic radiations – Islands, refugia and speciation • Refugia: an area in which a population of organisms can survive through a period of unfavorable conditions, especially glaciation.

Continental Separations • Continental Separations – Pangea (triassic, 220 my) – Laurasia – Gondwana (jurassic, 160 my) – N. America, Europe, Asia, S. America, Antarctica, Australia, Africa, India (cretaceaous, 100 my) New Land Bridges – Berringea, De. Geer/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.

Pangea Map Poster • Cut out the Pangea maps and glue them together (remember there will be 2 maps) • Define Macroevolution in your own words • Research which organisms match the bands on either map (5 organisms) – Why do these patterns exist? – How do these patterns support macroevolution? – The poster will be out of 16 marks

Pangea Map Poster Criteria /8 /2 /4 /2 /16