Chapter 26 Tree of Life. Where Are We Going? Taxonomy Scientific discipline of classifying and...
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Transcript of Chapter 26 Tree of Life. Where Are We Going? Taxonomy Scientific discipline of classifying and...
Chapter 26
Tree of Life
Where Are We Going?
TaxonomyScientific discipline of classifying and naming
organismsPhylogeny
Interpreting diagrams of evolutionary historyApplication
What evolutionary history says about biological diversity
Binomial Nomenclature
Common names for casual usage, but not accurateWhat animals come to mind you when hear the
word ‘fish’?Different words depending on language
Biologist use Latin scientific namesCarolus Linnaeus
2 part system: genus and specific epithetHomo sapiens or Panthera pardus
Hierarchical (Linnaean) ClassificationLinnaeus grouped named
animals into categoriesgenus Panthera: leopard
(P. pardus), lion (P. leo), tiger (P.tigris), & jaguar (P. onca)
Based on morphological similarities
Used by taxonomistsTaxon is any level of the
hierarchyReview: How can you
remember the hierarchical order of taxons?
Doesn’t always reflect evolutionary history
Phylogenetic TreesDiagrams hypotheses of
evolutionary history of organismsDegree of relatedness to
ancestorsUsed by systematists
Can reclassify if mistake found
Only implies pattern of descent, not time or age
Branch means common ancestor, not taxon from taxon
Reading Phylogenetic Trees
Which of the trees below depicts a different evolutionary history from the other two?
Series of branch points Root is last common ancestor of tree Sister taxa share an immediate ancestor
Homology vs AnalogyHomologies are similarities due to shared
ancestryUsed to construct phylogenies
Analogies are similarity due to convergent evolutionWhat is convergent evolution?
‘Moles’: marsupial vs eutherian; similar livesWings: bats vs. insects vs. birds; relation to cats
More points of resemblance make more likely ancestor was shared
Applies to morphological and molecularsimilarities
Constructing Phylogenetic Trees
Must first separate homologous from analogousSystematists then infer phylogeny using cladistics
Using common ancestry to classify organismsCreate clades or groups containing an ancestral
species and all descendants
Clades vs. Taxons
Similar to taxons because both are nested groupsEquivalent only if it is monophyletic, containing
ancestor and ALL descendantsParaphyletic contains ancestor and SOME
descendantsPolyphyletic contain taxa with different ancestors
Shared … Characteristics
Ancestral originates in an ancestor of the taxonBackbones are an example for mammals, why?
Derived is a novelty unique to a cladeHair is an example for mammals, why?
Ancestral can qualify as derived at deeper branchesWhat branch point allows backbones to be shared
derived characteristics?
Constructing PhylogeniesUse the 1st appearance of each shared derived characteristic
Determine the outgroup and ingroup
Determined from morphology, paleontology, embryonic development, or genes
Compare members of the ingroup to each other and to the outgroup
The Genome’s Role in PhylogenyNucleic acids and other molecules are also used
to determine and test hypotheses about evolutionary relationships
Important for organisms that are unlikely to have morphological similarities or organisms without fossil recordsFungi, plants, and animalsProkaryotes and other microorganisms
Determine relationships at all levels of the Tree of Life
Rates of gene evolution variesrRNA is slow = good for relationships that diverged
100’s of millions of years agomtDNA is rapid = good for recent evolution
Evolving GenomesOrthologous genes
Homologous genes in different species through speciation
Can diverge only after speciation
E.g cytochrome C (ETC protein)
Paralogous genes From gene duplication
= multiple copies in the same genome
Can diverge within a species
E.g 1000’s of olfactory receptors
Humans and mice 99% orthologous; and yeast 50%
The Changing Tree of LifeInitially 2 Kingdoms
Plants: bacteria (cell wall), chloroplast organims, fungi (sessile)
Animals: protozoans (movement and eat)5 Kingdoms
Monera: prokaryotesProtista: unicellular organismsPlantae, Fungi, and Animalia: eukaryotes
Recently 3 DomainsMolecular evidence that prokaryotes as different from
each other as eukaryotesBacteria: most prokaryotes, close to chloroplasts and
mitochondriaArchaea: diverse prokaryotes living in extreme
environmentsEukarya: cells with true nuclei
Domain Systems1 example of Life’s connectionsMost of living organisms are single-celledRed lines are multicellularMonera gone because it contains 2 domainsProtista disappearing due to diversity and similarity to other eukarya
Alternate Form of Life ConnectionHorizontal gene transfer: exchange of info between genomesMitochondrial ancestor of bacteria and eukaryaChloroplasts of bacteria and green plantsCan explain inconsistency of treesOnly diagrammable as a ring