Download History of Life and Homologies

History of Life
Biogeography | Homologies
History of Life
Learning Objectives
• Describe how biogeography and homology provide evidence for
evolution
• Distinguish between anatomical, molecular, and developmental
homologies
Fossil Record
• Fossil – the preserved traces or remains of living
organisms from the past
– See progressive change in organisms
Fossil Record
• Fossil record from
Equus genus
– Almost complete
– Supports theory
of common
ancestry
*Simplified fossil record
Fossil Record
• Stasis – the periods of time in the fossil record that show
limited change
Fossil Record
• Limitations of fossil
record
– Fossilization requires
specific conditions
– Organisms can appear
suddenly in fossil record
– Incomplete fossilization
results in gaps in fossil
record
Fossil Record
• Fossil record supports theory of sequential evolutionary
change
– Older fossils located in older strata
– Younger fossils located in younger strata
Fossil Record
• Ex) Sequential evolution of the coiled oyster
– Coiled oyster shells became
• Larger
• Thinner
• Flatter
Biogeography
• Biogeography – the
study of the distribution
of species, organisms,
and ecosystems through
geologic space and time
– Earth’s land masses have
moved over time
Biogeography
• Fossils provide evidence
of species that were
present across Earth’s
original land mass
• Allopatric speciation
occurred as land mass
split
– South American and
African monkeys share
common ancestor
Homologies
• Homology – the similar features between different
organisms resulting from common ancestry
– Anatomical
– Molecular
– Developmental
Homologies
• Anatomical homology – a group of similar structures
between different organisms resulting from common
ancestry
Homologous Structures
ARM
LEG
Flipper
Wing
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Homologies
• Vestigial structure – nonfunctional structure left over from
a common ancestor
– Ex) Pelvis in whale which lacks hind limbs
Homologies
• Anatomical homology
– Result of common
ancestor with that trait
• Convergent evolution
– Creates similar
structures/functions
– Are not anatomical
homologies
Homologies
• Molecular homology – the similar stretches of genetic
material between different organisms resulting from
common ancestry
– Shared genetic code indicates common ancestor
– Organisms likely to be related have retained same stretches of
DNA
#5 Molecular and Genetic
Evidence
 AKA Biochemical
Evidence
 Two closely-related
organisms will have
similar DNA, RNA, and
protein (amino acid)
sequences.
 This also gives
evidence of a common
ancestor.
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Homologies
• Developmental homology – the similar features in the
embryos of different organisms resulting from common
ancestry
– Hox genes – the sections of the genome that allow embryos to
develop structures in the correct place
– Similarities in development in different species indicate common
ancestry
#3 Embryology
 Embryo (early developmental stage) gives
evidence of evolution
 Identical larvae, different adult body
forms
 Similar embryos, related but diverse
organisms
 Shows
common
Larva
ancestry
Adult crab
Adult barnacle
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#3 Embryology
Vertebrates
all share gill
slits and a
tail in their
early
embryo
stage;
Share a
common
ancestor
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History of Life
Learning Objectives
• Describe how biogeography and homology provide evidence for
evolution
• Distinguish between anatomical, molecular, and developmental
homologies