BIOL Biodiversity, Classifying life, & Phylogenetic Trees

Biological Diversity (Biodiversity)

• Numbers of Species

  • 4-100 million species are currently extant (species currently living– opposite of extinct)

  • Newly discover 15,000 species yearly 

    • Sometimes species are hiding in plain sight– species can be mistakenly identified 

• Unequal Representation 

  • Why do we have a better count of some species compared to others?

    • Smaller species are harder to encounter

    • Some species are cryptic, they blend into their environment

    • Some species are located in difficult areas to investigate (the deep sea) 

    • Some species are just unpopular and not as cool

• Biosphere

  • All of the types of organisms and all their respective environments in the world

  • All life in the biosphere is interconnected due to the atmosphere

    • Waste, nutrients, water cleaning, food availability, pharmaceuticals all come from biodiversity

      • The recent loss of species is concerning– the planet is losing around 400-100,000 species lost per year

Systematics

the study of the diversity of organisms and their evolutionary relationship

Taxonomy

the science of naming, describing, and classifying organisms

Phylogeny

the evolutionary history of a group of organisms from a common ancestor

Binomial Nomenclature

Genus species

• Two part name

• Genus is more included– there can be multiple species that are in the same Genus. Genus can be used by itself.

• The species epithet is never used by itself– it's always used in conjunction with the genus.

Taxon (most broad to most narrow)

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

3 Domains of Life

• Bacteria

• Archea

• Eukarya

6 Kingdoms

• Bacteria

• Archea

• Eukarya

  • Protists (supergroup)

  • Plantae

  • Fungi

  • Animalia

Phylogenetic Trees

 basically an evolutionary hypothesis– gives insight on how organisms might be related to each other

(can be disproven, but as long as they are in place and not disproven they are useful to answering various questions)

Constructing Phylogenetic Trees

• Homologous structures

  • Things that come from the same source

  • Used to determine similarities in relationships

    • homology

    • homoplasy

    • shared derived characters / synapomorphies

• Choosing Criteria

  • Can be challenging– need to be cautious about what characteristics we’re using

  • Molecular traits– DNA & RNA sequences, Amino acids

• Taxa evolutionary relationships

  • Monophyletic taxon

  • Paraphyletic taxon (non-monophyletic)

  • Polyphyletic taxon

  → best to avoid paraphyletic and polyphyletic groups as they misrepresent the evolutionary relationships

Homology

•  presence of structures that are derived from a most recent common ancestor 

  • Ex) humans and bats– come from the same fundamental place

Homoplasy

•  appears to be homologous, but has independently acquired or lost in another branch

  • Based on convergent evolution– when unrelated organisms evolve similar characteristics 

    • Ex) the wings of insects are NOT homologous to the wings of birds and bats because those wings evolved from exoskeletons, not from four limbs 

Shared Derived Characters / Synapomorphies

• A character shared by everyone after a certain point, but is not present before that point 

  • Could be an anatomical structure, genetic trait, physiological characteristic, developmental characteristic, behavioral characteristic, or molecular 

Monophyletic taxon

Group where they share a most recent common ancestor

Paraphyletic taxon

Group where some of the descendants are not included and are left hanging— cut in two branches to get the group

• Ex) calling reptiles, “reptiles”, but excluding birds although they are descendants of reptiles 

Polyphyletic taxon

Have several lines/ branches that do not share the same most recent common ancestor