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Fields of Study in Animal Diversity Phylogeny Systematics Determining evolutionary relationships of organisms (the study of phylogeny). Taxonomy The evolutionary history of a species or group of related species. Assigning organisms to different categories based on their evolutionary relationships. Nomenclature The science of naming organisms The Kingdoms How are relationships – evolutionary relationships – determined? Structure Breeding behavior Geographical distribution Chromosome comparison Biochemistry These provide clues to how organism evolved Structure Many shared physical traits implies species are closely related Came from a common ancestor: Examples Lynx and bobcats have similar structure (skeletal) = more similarities than to any other groups Dandelions and sunflowers = similar flower and fruit structures Conclusion So what happens if you come across an unknown animal that can retract its claws similar to: Lions Tigers Bobcats Lynxes? What family should it belong to? Breeding Behavior What if two species live in the same area, and are similar in structure? What else could you do analyze to determine if one species, or two different? Look at breeding patterns Example • • 2 species of frog: – Hyla versicolor – Hyla chrysoscelis During mating season, the males make different sounds to attract females, only mate with females of their own species Geographical distribution • Location of species on Earth helps biologists determine relationships with other species • Similarities between species separated by large distances show common ancestry Example Many species of finches on the Galapagos Islands off the coast of South America Example How did the birds get there? Some members of species of finches from South America reached the Galapagos Islands These finches spread into different habitats and evolved into diverse species…but kept genetic similarities Chromosome Comparison Number and structure of chromosomes Example The following all look different, grow in separate climates, however they all have nearly identical chromosomal structure!! Cauliflower Cabbage Kale Broccoli Example Humans, gorillas and chimpanzees have chromosomes with similar appearances Chromosomal Comparisons Chromosomes of Unrelated Species Bacteria Other Species Conclusion Chromosomal similarities suggest a common ancestry Biochemistry Biochemical – DNA – evidence shows closely related species have similar DNA sequences Similar proteins Each specie’s DNA has a unique sequence and order: DNA is located on a small section of the chromosome Example ≠ ║ ║ Conclusion • The more similarities two species have between the sequence/order of their DNA molecule, the more closely related Unexpected Family Tree Currently, systematists use Structural, biochemical, fossil, and molecular comparisons to infer evolutionary relationships You Your Cousin! Morphological and Molecular Homologies In general, organisms that share very similar structures, breeding patterns or similar DNA sequences Are likely to be more closely related than organisms with vastly different structures or sequences. Not always true! Analogy vs. Homology Homology Homologous Structures – structures in different species that are similar because of common ancestry. Analogy Analogous Structures – similarity in structures due to adaptations from similar evolutionary pressures (convergent evolution) and not a common ancestor. Convergent evolution occurs when similar environmental pressures and natural selection Produce similar (analogous) adaptations in organisms from different evolutionary lineages Australian Mole – marsupial mammal North American Mole – placental mammal Sorting Homology from Analogy • A potential misconception in constructing a phylogeny – Is similarity due to convergent evolution, called analogy, rather than shared ancestry Ex: Humans, gorillas, and ravens have the ability to problem-solve, and are highly intelligent. Humans and gorillas share ancestry: homology. Ravens are in a separate phylum (birds), so developed their intelligence separately from humans. Linking Classification and Phylogeny Systematists depict evolutionary relationships In branching phylogenetic trees Each branch point Represents the divergence of two species “Deeper” branch points Represent progressively greater amounts of divergence “KLADOS” = Greek word meaning “BRANCH” or “SPROUT” Cladogram - a shows pattern of shared, inherited characteristics; a “graphic organizer” based on measurable traits and not evolutionary relationships. Cladogram for Transportation Wheels are the most ancestral (oldest). Wings are the most derived (newest). Construct a Cladogram for Us! Gorilla Four limbs Fur No tail Tiger Four limbs Fur Tail Lizard Four limbs Tail Fish Tail Chimpanzee Four limbs Fur No tail Clade With 4 Limbs Clade With Fur Clade With No Tail Characteristics (Traits) for Constructing this Cladogram Tail is the most ancestral Four limbs is the oldest derived trait Fur is a later derived trait Loss of tail is the most derived trait One Possible Cladogram Four Limbs Where’s the Tail? How do we know the gorilla and chimpanzee have lost their tail? Sometimes cladists must compare embryological development and internal anatomy to determine relatedness. May not be exactly the same structures. Coccyx- Primate Vestigial Tails Gorilla Pelvic Girdle Human Pelvic Girdle Vestigial Structure - historical remnants of a structure that has little or no use in a modern organism but had a function in ancestors. A Vertebrate Cladogram Lancelet Vertebrae Birds Mammals Reptile Feathers Amphibian Fur Fish Endothermic Lancelet Amniotic Egg Four Limbs Vertebrae What is the shared primitive character for this clade? Ans: Birds Reptile Mammals Feathers Amphibian Fur Fish Endothermic Lancelet Amniotic Egg Four Limbs Vertebrae What is the shared derived character for amphibians, reptiles, birds & mammals? Ans: Four Limbs For reptiles, birds & mammals? Ans: Amniotic Egg Phylogenetic Trees and Timing A cladogram is not a phylogenetic tree; may need more information (fossils, molecular systemics, etc.). Any chronology represented by the branching pattern of a phylogenetic tree Is relative rather than absolute in terms of representing the timing of divergences. Phylograms In a phylogram: The length of a branch reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineage. A phylogram of homologous hedgehog genes. Outgroup Ultrametric Trees In an ultrametric tree: The branching pattern is the same as in a phylogram, but all the branches that can be traced from the common ancestor to the present are of equal length. Outgroup A Rule about Phylogenetic Trees William of Ockham – 14th Cent. English philosopher, stated that, when all qualities of hypotheses are equal, the simplest explanation for a phenomenon is usually correct; Occam’s Razor: "entities must not be multiplied beyond necessity" (entia non sunt multiplicanda praeter necessitatem). Parsimony – stingy, economical, fewest complications.
