Transcript Chapter 4: Speciation and Phylogeny

Chapter 4: Speciation and
Phylogeny
Macroevolution
•Species and Speciation
•Phylogenies: Evolutionary Trees
Biological Species
• Reproductive isolation
– Gene flow within species
– No gene flow between species
• Allopatric speciation: results from
geographic/environmental isolation
– Selection or gene drift will eventually change
each population in different directions and
eventually they will be incapable of
interbreeding
• Sympatric Speciation: Niche diversification
– Different ways of making a living in the same
place.
– Specialization toward different resource
gathering strategies leads to different
selective forces
• Sympatric Speciation: Niche diversification
– Different ways of making a living in the same
place.
– Specialization toward different resource
gathering strategies leads to different
selective forces
Time
– Darwin’s finches
– Adaptive radiation
Other isolation mechanisms
– Mechanical isolation
– Temporal isolation
– Behavioral isolation
Seagulls around the World
Phylogenies: Trees of Life
• Linnaeus: Linnaean System of Classification
• Based on similarity of traits
• Hierarchical:
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Kingdom
Phylum
Class
Order
Family
Genius
Species
Kings Play Chess On Fine Grained Sand
Keep Pots Clean Or Family Get Sick
Humans are:
Kingdom:
Phylum:
Class:
Order:
Family:
Genius
Species
Animal
Cordates (Sub phylum Vertebrata)
Mammal
Primate
Hominid (Super Family Hominoid)
Homo
Sapiens
Phylogeny for the Hominoids
Inheritance or Convergence?
• Homologous = Similar because of
common decent (share a recent common
ancestor) – Inheritance.
• Analogous = Similar because of
adaptation to the same or similar
environmentally stable problem (Bird and
Bat wings) - Convergence.
Phylogenies use homologous
structures (traits) and must avoid
analogous structures
Present
Past
Yes
Derived Trait
(last common ancestor)
No
Analogous Trait
(convergence)
No
Ancestral Trait
(common ancestor of all 3)
Using Overall Similarity of Traits Leads to the Wrong Family Tree
Using Similarity of Derived Traits Leads to the Correct Family Tree
Using Similarity of Derived Traits Leads to the Correct Family Tree
Systematics: the study that distinguishes
ancestral from derived traits
Ancestral Traits
• Appear earlier in embryonic development
– Ontology recapitulates phylogeny
• Appear earlier in the fossil record
– Older traits
• Seen in out-groups
– If a trait is absence in one species but seen in
other more distant lineages (tails)
Genetic Distance
• DNA Hybridization
Less Related
Fewer bonds
Lower Temp to break
More Related
More bonds
Higher Temp to break
Molecular Clock
Neutral theory or Natural selection?
How Good are Human Phylogenies
•Cladistic modeling of skeletal traits do not match the cladistic modeling of DNA
distance
•Human phylogenies are based on skeletal data and are likely to have errors.
Some argue for Bastian statistics approach.