EVIDENCE OF EVOLUTION. Key Concepts What evidence supports the theory of evolution? How do...
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Transcript of EVIDENCE OF EVOLUTION. Key Concepts What evidence supports the theory of evolution? How do...
EVIDENCE OF EVOLUTION
Key Concepts
• What evidence supports the theory of evolution?
• How do scientists infer evolutionary relationships among organisms?
• How do new species form?
Key Terms
Homologous Structures– Body parts that are structurally similar
in related species.
Key Terms
Branching tree– A diagram that shows how scientists
think different groups of organisms are related.
Identifying SupportingEvidence
• Identifying supporting evidence helps us understand the relationship between the facts and the hypothesis.
• Evidence consists of facts that can be confirmed by testing or observation.
Supporting Darwin’s Theory
• Fossils show that organisms that lived in the past were very different from organisms alive today.
• Patterns of early development show that some different organisms look similar during their early stages.
• Similar body structures in different species show that the organisms shared a common ancestor.
Interpreting the Evidence
• FOSSILS
• EARLY DEVELOPMENT
• BODY STRUCTURE
FOSSILS
• The preserved remains or traces of an organism that lived in the past.
• Fossils show that organisms that lived in the past were very different than organisms alive today.
• Scientists use fossils to infer the structures of ancient organisms.
EARLY DEVELOPMENT(embryology)
• Scientists compare the early development of different organisms to make inferences about evolutionary relationships.
• Similarities in early development among different organisms suggests that they are related and share a common ancestor.
BODY STRUCTURE(homologous structures)
• Darwin compared body structures of living species when observing the species on the Galapagos Islands.
• Body structure is an organism’s body plan, how its bones are arranged.
• Similarities in body structure provide evidence that organisms evolved from a common ancestor.
Species Relationships
• Fossils, early development patterns, and body structure provide evidence that evolution has occurred.
• Scientists also have used these kinds of evidence to infer how organisms are related to one another.
New Evidence
• DNA
• Protein Structure
Similarities in DNA• Scientists compare the
genes of different species to determine how closely related the species are.
• The more similar the sequence of bases in the DNA, the more closely related the species are.
• The more similar the order of amino acids (codes for proteins) in the DNA, the more closely related the species are.
Combining Evidence
• The use of DNA and protein structure has confirmed conclusions that scientists had already based on fossils, embryos, and body structure.
• The use of DNA and protein structure has also caused scientists to “revise” the branching trees of some species.
Branching Trees
• Branching trees show common ancestry (phylogeny).
• Evolution is about gradualism and phylogeny.
How Do New Species Form?(speciation)
• A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits.
• Isolation/Separation– River– Volcano– Mountain range
Convergent Evolution
• The process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
Divergent Evolution(adaptive radiation)
• The process by which related species evolve different traits.
Gradualism
Evolution occurs slowly but steadily.