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WHAT IS THE EVIDENCE FOR EVOLUTION ?

WHAT IS THE EVIDENCE FOR EVOLUTION ?. Overall it is broken into 3 over arching categories: 1. Anatomical Structures (fossil records, homologous structures, and morphology fall under this area) 2. Genetic information 3. Embryonic Development or Embroylogy Let’s take a closer look….

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WHAT IS THE EVIDENCE FOR EVOLUTION ?

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  1. WHAT IS THE EVIDENCE FOR EVOLUTION? Overall it is broken into 3 over arching categories: • 1. Anatomical Structures (fossil records, homologous structures, and morphology fall under this area) • 2. Genetic information • 3. Embryonic Development or Embroylogy Let’s take a closer look…

  2. WHAT IS THE EVIDENCE FOR EVOLUTION? • THE FOSSIL RECORD • MORPHOLOGY • HOMOLOGOUS BODY STRUCTURES • SIMILARITIES IN EARLY DEVELOPMENT

  3. Phylogeny and the Tree of Life

  4. Taxonomy • The science of classifying organisms based on shared characteristics

  5. Overview: Investigating the Tree of Life • Phylogeny is the evolutionary history of a species or group of related species (usually organized into a phylogenetic tree) • Phylogenetic trees and cladograms arrange organisms based on common ancestry

  6. Phylogenetic Trees and Cladograms • Each branch point represents the divergence of two species • Sister taxa are groups that share an immediate common ancestor • A rooted tree includes a branch to represent the last common ancestor of all taxa in the tree • A polytomy is a branch from which more than two groups emerge

  7. What Phylogenetic Trees DO & DO NOTShow Us • DO: show patterns of descent • DO NOT: tell when species evolved or how much genetic change occurred in a lineage • DO NOT:assume that a taxon evolved from the taxon next to it

  8. What is the difference between a phylogenetic tree and a cladogram? Phylogenetic tree – a longer branch = a longer amount of time has passed in the lineage • In phylogenetic trees, branch lengths can represent the amount of genetic change or are proportional to time • In cladograms, the branch lengths don’t mean anything Cladogram – line length doesn’t matter

  9. How to read a cladogram • This diagram shows a relationship between 4 relatives. These relatives share a common ancestor at the root of the tree. • Note that this diagram is also a timeline. The older organism is at the bottom of the tree. • The four descendants at the top of the tree are DIFFERENT species. This is called SPECIATION. • Speciation – the formation of new and distinct species in the course of evolution

  10. How to read a cladogram • Branches on the tree represent speciation • The event that caused speciation is shown as a fork on the tree.

  11. How to read a cladogram • Species B and C each • have characteristics • that are unique only to • them. • • But they also share • some part of their • history with species A. • This shared history is • the common ancestor.

  12. How to read a cladogram Write a sentence that summarizes therelationship between A and B. What is the only thing A and B have in common?

  13. How to read a cladogram • A CLADE places species into groups that includes an ancestral species and all of its descendants. • If you cut a branch of the tree you could remove all the organisms that make up a clade

  14. How to read a cladogram • Which number would indicate the location of an ancestor shared by primates, rabbits, crocodiles, and birds? • Which number would indicate the location of an ancestor shared by crocodiles and birds? 5 4 3 2 1

  15. What evidence are phylogenetic trees and cladograms based on? • Morphologies, genes, and biochemistry of living organisms • Organisms with similar morphologies or DNA sequences are likely to be more closely related • Must distinguish whether a similarity is the result of homology or analogy • Homology is similarity due to shared ancestry • Analogy is similarity due to convergent evolution (shark/dolphin)

  16. WHAT IS THE EVIDENCE FOR EVOLUTION? • THE FOSSIL RECORD • MORPHOLOGY • HOMOLOGOUS BODY STRUCTURES • SIMILARITIES IN EARLY DEVELOPMENT

  17. EVIDENCE OF EVOLUTION Morphology: Humans share many characteristics with our close relatives, other mammals. Some of these are obvious. We all have four limbs, two eyes, two ears, lungs and a skeleton. But we also have features in common with more distantly-related species, including worms, and even single-celled organisms like amoeba. This is evidence that all organisms on Earth, whether living or extinct, are related, and that we all evolved from a common ancestor

  18. Which one is a human skull?

  19. What evidence are phylogenetic trees and cladograms based on? • Genes/DNA • Similar DNA = more likely to be closely related • Morphology – the structure of the organism (internal & external) • Similar structures = more likely to be closely related • Embyrology– study of animals before birth

  20. Morphology (continued)- • Homologous structures – organs or bones in different animals that have similar structures • b/c of shared ancestry HOMOLOGOUS STRUCTURES- STRUCTURES THAT HAVE DIFFERENT MATURE FORMS IN DIFFERENT ORGANISMS, BUT DEVELOP FROM THE SAME EMBRYONIC TISSUE. • The opposite of this is “analogous structures” – similar structures that formed in animals adapting to similar environments or circumstances (shared ancestry is NOT the cause)

  21. HOMOLOGOUS STRUCTURES STRUCTURES THAT HAVE DIFFERENT MATURE FORMS IN DIFFERENT ORGANISMS, BUT DEVELOP FROM THE SAME EMBRYONIC TISSUE.

  22. You try, identify the homologous structures between these different animals (use 5 colors). Carpals Metacarpals and phalanges

  23. WHAT IS THE EVIDENCE FOR EVOLUTION? • THE FOSSIL RECORD • MORPHOLOGY • HOMOLOGOUS BODY STRUCTURES • SIMILARITIES IN EARLY DEVELOPMENT

  24. What evidence are phylogenetic trees and cladograms based on? • Embryology– embryos of different animals look very similar in early stages • Difficult to tell them apart Can you tell which one is the human? What about now? Which one is the human?

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