History, life history, and ecology of the invertebrates

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History, life history, and ecology of the
invertebrates Chapter 1
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The three domains all organisms

• Domain Archaea prokaryotes
• Domain Eubacteria
• Domain Eukaryota
• Kingdom Fungi
• Kingdom Plantae eukaryotes
• Kingdom Protista
• Kingdom Animalia

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Most animals are invertebrates

• 1 million species described
• 47,000 species of animals described
• millions of species are undescribed
• among the animals 95 are invertebrates

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Where did life come from?
Theories 1. From a primordial soup in
the early atmosphere 2. At deep-sea
hydrothermal vents (Archaea) 3. From
cosmogenic material
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Discuss with your group

• Which organisms appeared first on Earth?
• What types appeared afterwards?
• Which groups do you expect to have the greatest
  diversity ( species or types) very old or very
  young groups?

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Brief timeline

• 4.6 billion years ago (bya) Earth formed
• 3.6 bya disputed fossils of bacteria
• 2.7 bya first eukaryotic cells
• 600 million years ago (mya) metazoa
• 500 mya all extant phyla existed
• 470 mya terrestrial life arose

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Highlights over evolutionary time

• Ediacarian fauna (600 570 mya)
• - fossil beds of soft-bodied species, traces
• Cambrian period (570 500 mya)
• - explosion rapid radiation
• - skeletons, bilaterality, predators appear
• Permian / Triassic boundary ( 250 mya)
• - mass extinction 85 marine species
• Cretaceous / Tertiary boundary ( 65 mya)
• - mass extinction 50 all species

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Why are so many invertebrates marine? ( but not
the insects!!!)

• Life began in the oceans
• Oceans buffer conditions
• stable temperature, salinity, pH
• The switch to freshwater land is hard
• Productivity is high in oceans

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Habitat organismal vocabulary

• Littoral
• Intertidal
• Pelagic vs. benthic
• Epifaunal / Infaunal / Interstitial
• Errant vs. sessile
• Photic vs. aphotic zone
• Nektonic vs. planktonic
• Phytoplankton vs. zooplankton

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Common invertebrate habitats

• Oceans (all depths)
• Estuaries
• Freshwater habitats
• Terrestrial habitats

Discuss with your group Which do you think has
the most stable conditions? The least stable
conditions? What is difficult about life in each
habitat?
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Symbiotic interactions
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Evolutionary biology is changing!!

• Advances in molecular biology
• Advances in phylogenetic methods
• Changes in evolutionary ideas (macroevolution vs.
  microevolution)

So be critical of phylogenies
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Microevolution

• Probably most familiar
• Within-species evolution of populations
• Shifts in gene frequencies
• Driven by natural selection
• Acts upon genetic variation from recombination,
  mutation, genetic drift
• Slow evolutionary change, at species level

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Macroevolution

• New species arise
• Explosive, rapid radiation of lineages
• Major developmental shifts
• Mass extinctions
• Rapid evolutionary change, above species level

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Discuss with your group

• Does evolution occur gradually slowly, over
  millions of years, or does it happen dramatically
  and rapidly?
• What is punctuated equilibrium?

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Homeobox (Hox) genes

• Regulatory genes that control developmental genes
• Determine basic geometry of organism
• segmentation
• identities of segments
• anterior / posterior poles of organism
• limb placement
• Probably have been very important in evolution

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