Warm-Up Contrast adaptive radiation vs. convergent evolution? Give an example of each. What is the correct sequence from the most comprehensive to least comprehensive taxon? In a population of 500 rabbits, 320 are homozygous dominant for brown coat color (BB), 160 are heterozygous (Bb), and 20 are homozygous white (bb). What are the frequencies of the alleles (B and b)? What are the frequencies of the different genotypes (BB, Bb, and bb)?

Phylogeny and the Tree of Life Chapter 26 Phylogeny and the Tree of Life

What you need to know: The taxonomic categories and how they indicate relatedness. How systematics is used to develop phylogenetic trees. The three domains of life including their similarities and their differences.

(evolutionary history) Systematics: classifying organisms and determining their evolutionary relationships Taxonomy (classification) Systematics Phylogenetics (evolutionary history)

Tools used to determine evolutionary relationships: Fossils Morphology (homologous structures) Molecular evidence (DNA, amino acids) Who is more closely related? Animals and fungi are more closely related than either is to plants.

Taxonomy: science of classifying and naming organisms Binomial nomenclature (Genus species) Naming system developed by Carolus Linnaeus.

REMEMBER!! Dear King Philip Came Over For Good Spaghetti Dear King Philip Crossed Over Five Great Seas Dear King Philip Came Over From Germany Stoned Your own???

Phylogenetic Tree Branching diagram that shows evolutionary history of a group of organisms

Simple trees European wildcat Domestic cat South China Tiger IMAGES FROM: Wikimedia Commons

Ancestor of domestic cat and wildcat European wildcat Ancestor of all three cats Tiger

Human Gorilla Chimpanzee IMAGES FROM: Wellcome Images / Wikimedia Commons

Extant species Hypothetical ancestors Human Chimpanzee Root (common ancestor) Outgroup Branch Gorilla

Cladogram Phylogram Branch length shows evolutionary change or time (or both) Branch length does not indicate evolutionary change or time

Rooted tree Unrooted tree Relationships and the order of events are shown Only relationships are shown

Three possible layouts Circular (rooted) tree Unrooted tree Rooted tree

Constructing a phylogenetic tree A 0 indicates a character is absent; a 1 indicates that a character is present.

Branch lengths can represent genetic change

Branch lengths can indicate time

Build your own tree

Living (extant) species Common ancestor (fossil)

Extant species Common ancestor

Possible answers

Tree 1

Tree 2

Tree 3

Problems

Convergent evolution Vertebrate eye Octopus eye Nerve fibres Retina Blind spot Optic nerve Optic nerve Vertebrate eye Octopus eye IMAGE FROM: Caerbannog. Wikimedia Commons

different trees are possible Rhesus monkey Squid Bacterium Tiger Herring Snail Dog Octopus Baboon Coelacanth Fox Turbot Lemur Chimpanzee Oak tree Cat Redwood tree Gibbon Pine tree Human With 20 species 8, 200, 794, 532, 637, 891, 559, 375 different trees are possible Only one is right

Human Bacterium Coelacanth Cat Tiger Dog Fox Baboon Rhesus monkey Chimpanzee Gibbon Lemur Herring Turbot Snail Octopus Squid Redwood tree Pine tree Oak tree

Draw a phylogenetic tree based on the data below Draw a phylogenetic tree based on the data below. Draw hatch marks on the tree to indicate the origin(s) of each of the 6 characters.

Answer:

Cladogram: diagram that depicts patterns of shared characteristics among taxa Clade = group of species that includes an ancestral species + all descendents Shared derived characteristics are used to construct cladograms Turtle Leopard Hair Amniotic egg Four walking legs Hinged jaws Vertebral column Salamander Tuna Lamprey Lancelet (outgroup) Cladogram

Monophyletic, paraphyletic, and polyphyletic groups

Monophyletic A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants

Paraphyletic A paraphyletic grouping consists of an ancestral species and some, but not all, of the descendants

Polyphyletic A polyphyletic grouping consists of various species that lack a common ancestor

Outgroups An outgroup is a species or group of species that is closely related to the ingroup, the various species being studied Systematists compare each ingroup species with the outgroup to differentiate between shared derived and shared primitive characteristics Outgroup comparison assumes that homologies shared by the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor It enables us to focus on characters derived at various branch points in the evolution of a clade

Practice Use the four cladograms below to answer the following questions: (5) a. Which cladograms have identical topologies (show the same pattern of relationships)? b. On tree 1, circle two different monophyletic groups. c. On tree 2, can you circle those same monophyletic groups. If so, do it! d. On tree 3 circle a paraphyletic group. E. On tree 4, which organisms are more closely related B and C or C and D. How can you tell?

More Practice Answer the questions associated with the following tree: a. Circle the monophyletic group that includes Mimes & Carnies. b. Which group(s) are most closely related to Carnies? c. Are Clowns, Jugglers & Comedians a monophyletic group? If not, who else would need to be included? d. Who is more closely related to Jugglers: Mimes or Clowns, or are they equally related? e. What type of trait is “uses face paint” (e.g. shared ancestral, derived, etc.)?

Principle of maximum parsimony: use simplest explanation (fewest DNA changes) for tree – “keep it simple” Molecular clocks: some regions of DNA appear to evolve at constant rates Estimate date of past evolutionary events Eg. Origin of HIV infection in humans= 1930’s

Tree of Life 3 Domains: Bacteria, Archaea, Eukarya

Identification of species SYSTEMATICS focuses on phylogeny Biological diversity taxonomy cladistics classification Identification of species D K P C O F G S Homologous similarities fossils binomial molecular Genus, species morphology