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Evolution: Speciation
and More Evidence
Evolution is a FACT
Outline
1. Key concepts
2. Speciation
3. More evidence
4. Conclusions
Key Concepts:
A species consist of one or more populations of
individuals that can interbreed and produce
offspring
Speciation is the process by which daughter species
evolve from a parent species
All species that have ever lived are related
Comparative anatomy help reconstruct patterns of
change through time
Biochemical comparisons also provide evidence of
evolution
Speciation
The process by which daughter species
evolve from a parent species
Speciation occurs as results of
Natural selection
Genetic drift
Mutation
Move Evidence
Various types of evidence help scientists
determine evolutionary relationships
among organisms
1.
2.
3.
4.
5.
The fossil record
Fossil dating
Comparative anatomy
Comparative embryology
Molecular biology
The fossil record
Fossil: any record of a dead
organism, frequently preserved
in stratified, sedimentary rocks
Older strata below, newer strata
above, provide relative record
of geologic time and of hardbodied organisms alive at that
time
Fossil dating
Radiocarbon dating method:
• Depends on ratio of radioactive
carbon (14C) to stable, nonradioactive
form, 12C in fossil
• New 14C continually formed and
added into living cells but stops
when organism dies
• Fossil 14C decays, so ratio changes in
fossil with half-life of ~5000 years
Strata of sedimentary rock at the Grand Canyon
Descent with modification
Comparative anatomy
Evolutionary relationships determined by
examining anatomical structures:
Homology
Similarity in body parts in different organisms
Attributable to descent from a common ancestor
Analogy
Similarity in body parts in different organisms
Attributable to similar environmental pressures
Homologous Structures
Vertebrate forelimbs
Comparative anatomy
Comparative embryology
•
•
Embryonic stages
of many
organisms similar
despite adult
differences
Suggests
relationships
among those
organisms derived
from some
common ancestor
Similar Vertebrate Embryos
Adult
shark
Aortic arches
Two-chambered
heart
Early
human
embryo
Certain veins
Molecular biology
Mutation (change) in DNA is basis for
evolutionary change
Homology in base sequences between
two organisms suggests evolutionary
relationship
More homology, closer relationship;
less homology = more mutations so
more distant relationship
Comparative Biochemistry
Kinds and numbers of biochemical
traits that species share is a clue to
how closely they are related
Can compare DNA, RNA, or
proteins
More similarity means species are
more closely related
Comparing Proteins
Compare amino acid sequence of proteins
produced by the same gene
Human cytochrome c (a protein)
Identical amino acids in chimpanzee protein
Chicken protein differs by 18 amino acids
Yeast protein differs by 56
Molecular biology
Constructing evolutionary trees
Trees are graphs of relationships
among various organisms and groups
of organisms
Pattern of relationships shown on
horizontal axis; time on vertical axis
Can estimate rates of evolution among
different groups
Constructing evolutionary trees
In Conclusion
A species consists of individuals in a
population or populations
Genetic divergence is a buildup of
differences in allele frequencies between
populations
Speciation is the process by which species
form a population of a parent species
In Conclusion
There is extensive evidence of evolution
based on similarities and differences in
body form, function, behavior, and
biochemistry
Comparative biochemistry has
identified similarities and differences
among species