Transcript macroevolution

• 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.