The variety of life

1. What are species, families, domains?
   • What are the three domains of life?
2. What is the history of Life on Earth
   • Biodiversity: the # species today (1 - 100 x 10⁶)
   • A fraction (<99%) of all species that have lived Background Extinction: every 4 yrs (bird, mammal)
     vs. Mass Extinction Example: Phanerozoic Marine
   
   Any discussion of biodiversity should begin with the The Tree of Life
   You should also have a look at the Endangered Species Page (U.S. Fish & Wildlife Service)

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What is a species?

• a species includes sexually reproducing organisms that, when they breed, produce live, fertile offspring
  
• Example: horses & donkeys Equus species,
  but not mules or zorse
  ♂ donkey ♀ horse = mule
  ♂ horse ♀ donkey = hinny Wikipedia
• Example: blue & foothills paloverde Parkensonia

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Formal (Latin) species names vs. common names

• Formal names are unique, and commonly describe some characteristic feature
        Ursus horribilis [firstpeople.us] --> &
        Homo neanderthalensis [New Anatomist]
• Common names are NOT unique. What a Californian calls a ' bumblebee,' an easterner calls a 'yellow jacket,' and what a Californian calls a 'yellow jacket,' an easterner calls a 'wasp.'

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Taxonomy above the Species

• Kingdom-- Animalia (animals) (below domains)
• Phylum--Chordata (have notochord)
• Class--Mammalia (nurse young)
• Order--Primates (ex: lorises, monkeys, apes)
• Family--Hominidae (ex: Homo, Pan, Gorilla)
• Genus--Homo (ex: sapiens, neanderthalensis, erectus)
• Species--sapiens
  • Subspecies--sapiens

* Homo sapiens
Taxonomy Examples

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Three Domains:

• Archaea (Prokaryotic)
• Bacteria (Prokaryotic)
  Eubacteria
  Cyanobacteria (blue-green algae)
• Eukarya -- (Eukaryotic) all others;
  
  Protists
  Fungi
  Plants
  Animals--Animalia
* You Are Here

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Origin of life (what is life)

Chemical evolution

• 4.7-3.8 billion years ago (Hadian eon)
  
  • Early atmosphere (O₂) - H₂O, HCN, N₂, CO, CO₂, CH₄, C₂H₆, NH₃, H₂S, HCl (cf. Titan)
  • Electrical & Geothermal energy transforms these gases into amino acids, sugars & bases
  • "RNA World" now: DNA > RNA > protein

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Biological evolution I

• 3.8-2.1 billion years ago (Archean)
  
  
  
• Prokaryote World
  • Before ca. 2.3 Gyr: bacteria + archea only
    RESPIRATION only
        CH₂O + O₂ => H₂O + CO₂
  • Thereafter: Cyanobacteria (blue-green algae) PHOTOSYNTHESIS (2.32 Gyr)
       H₂O + CO₂ => CH₂O + O₂

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Biological evolution II

• 2.1-0.65 billion years ago (Proterozoic)
  
  
  
• Eukaryote World - with organelles dominate
• 2.1 Gy First multicellular Eukaryotic organisms
• ENDOSYMBIOSIS: mitochondria, chloroplasts, golgi ...

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Biological evolution III

• 0.65 billion years ago to present (Phanerozoic)
  
  
• Origin and development of modern organisms
  Edicarian Fauna movie
  Cambrian Explosion 510 My
  Invasion of land by plants 400 My
• Paleo- Meso- Cenozoic

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KEY DATES in the Evolution of Life on Earth

• 4.7 Gy begin chem evolution
   ??  RNA-world
• 3.8 Gy begin prokaryotes
• 2.3 Gy begin photosynthesis
• 2.1 Gy begin eukaryotes
• 0.65 Gy diversification of modern
• 0.40 Gy land plants

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