History of LifeBiogeography | Homologies
Learning Objectives• Describe how biogeography and homology provide
evidence for evolution• Distinguish between anatomical, molecular, and
developmental homologies
History of Life
• 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
Fossil Record
*Simplified 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
Fossil Record
• 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
Biogeography
• 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
Homologies
Homologous StructuresARM LEG Flipper Wing
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• Vestigial structure – nonfunctional structure left over from a common ancestor– Ex) Pelvis in whale which lacks hind limbs
Homologies
Homologies
• Anatomical homology– Result of common
ancestor with that trait
• Convergent evolution– Creates similar
structures/functions
– Are not anatomical 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
Homologies
#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. 17
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• 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
Homologies
#3 Embryology Embryo (early developmental stage)
gives evidence of evolution Identical larvae, different adult body
forms Similar embryos, related but diverse
organisms Shows
commonancestry
Larva
Adult barnacleAdult crab
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#3 Embryology
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Vertebrates all share gill slits
and a tail in their early
embryo stage;
Share a common ancestor
Learning Objectives• Describe how biogeography and homology provide
evidence for evolution• Distinguish between anatomical, molecular, and
developmental homologies
History of Life