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Pests, Plagues & Politics Lecture 4. How Insects Got Where They Are!!. Or Insect Evolution. Key Points Insect Evolution. Evolution by Natural Selection Survival of the Fittest The 5 Principles How is Paleoentomology important? Evolutionary Timeframes Important events in insect evolution.

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key points insect evolution
Key PointsInsect Evolution
  • Evolution by Natural Selection
    • Survival of the Fittest
    • The 5 Principles
  • How is Paleoentomology important?
  • Evolutionary Timeframes
  • Important events in insect evolution
slide5

Alfred Russell Wallace

Charles Darwin

  • Brit.
  • 1823 – 1913
  • Interests in
    • Botany
    • Entomology
  • So. America
  • SE Asia
    • 1854 to 1862
  • Brit.
  • 1809 – 1882
  • Interests in
    • Botany
    • Entomology
  • So. America
    • 1831 to 1836
charles darwin
Charles Darwin
  • 1859
    • The Origin of Species

“I have called this principle,

by which each slight variation,

if useful, is preserved, by the term

Natural Selection.”

evolution via natural selection
Evolution via Natural Selection
  • A theory independently derived by Wallace & Darwin.
  • Simplistically summarized as:
    • “Survival of the Fittest”

by the English philosopher Herbert Spencer

  • Survival = placement of your genes into the next
  • generation
  • Fittest = your ability to get your genes into the
  • next generation
selective pressure
Selective Pressure

Forces (usually environmental change) that select

for (in favor of) those organisms that are best suited

to survive the change.

Selective pressure also selects against those organisms

that are not able to “cope” with change.

evolution by natural selection works on the principle of differential reproduction
Evolution by Natural Selectionworks on the principle of differential reproduction
  • Natality - more individuals are born into a generation than will survive and reproduce.
  • Variability - there is variation between individuals in any given population.
  • Survivorship - individuals with certain characters have a better chance of surviving and passing along their genes
natural selection cont
Natural Selection, cont.
  • Heritability
    • at least some of the characteristics responsible for differential reproduction are genetically mediated.
  • Time
    • enormous spans of time are involved in evolutionary change.
insect evolution
Insect Evolution
  • Bugs do not make particularly good fossils
  • Phylum Cordata (vertebrates)
    • 33% of total known species have fossil representatives
  • Phylum Arthropoda (Class Insecta)
    • 1% of total species have a fossil record
paleoentomology
Paleoentomology
  • The study of prehistoric insects
  • Best preserved insect fossils are from ambers
  • How many orders of insects?
    • Extant = 27
    • Extinct adds another 55!

Flash:

oldest salvaged DNA is from an amber termite ca. 100 mya.

slide13

FYI

CT Scan of an amber

Insect inclusion

A 100 mya wasp.

slide14

FYI

A North American Honey Bee

Compression

Fossil

14 mya

Nevada

newest oldest bee fossil

FYI

Newest {Oldest} bee fossil

35 – 46 mya

Melittosphexburmensis

slide16

FYI

Coleoptera – Aquatic beetle

Cretaceous

Hymenoptera

Eocene

phylogeny a family tree
PhylogenyA family tree
  • A phylogeny is based largely on morphological & structural similarities between groups.
  • And while the fossil record is far from complete, it can be used to trace the outlines of insect evolution
evolutionary time frames
Evolutionary Time Frames
  • Micro-evolution - changes in populations that happen in a time scale of decades.
  • Speciation - changes over a longer time frame that result in the appearance of new species - hundreds of thousands of years
  • Macro-evolution - major changes in phylogenetic patterns over long time scales and broad geographical areas.
events of note
Events of Note
  • Earth – 4.5 billion years old
  • Precambrian – 3.1 bya
    • Prokaryotes
  • Cambrian – 600 mya
    • First abundant fossils (metazoans)
  • Silurian – 425 mya
    • Invasion of land by arthropods
events of note1
Events of Note
  • Devonian – 400 mya
    • First true insects
  • Carboniferous – 345 mya
    • First great radiation of insects
  • Cretaceous – 135 mya
    • Second great radiation of insects
  • Tertiary - 63 mya
    • Dominance of the land by mammals, birds & insects
  • Quaternary – 2 mya
    • First Homo
insect evolution1
Insect Evolution
  • Insects (as a group = taxon)
    • Evolved from the Annelids (the worms)
    • Ca. 400 mya
  • Most primitive (oldest) Insect orders
    • TheAPTERYGOTES, wingless
    • Devonian, ca. 400 mya
      • Thysanura
        • The bristle tails & silverfish
      • Collembola
        • The Springtails
slide24

The development of wings

The Pterygotes: 350 mya

Primitively winged insects known as PALEOPTEROUS

Simple wing articulation

Seen today in the orders:

Odonata = the dragonflies

Ephemeroptera = the mayflies

slide25

Dragonfly - Odonata

Mayfly - Ephemeroptera

slide26

The development of the wing flexion mechanism

Neoptera (new or “modern” wing)

300 mya

Today this covers 97% of all extant species

Snakefly

Rhaphidioptera

slide27

Development of Complete Metamorphosis

(holometabolous)

Ca. 290 mya

(note: soon after the wing flexion mechanism)

Benefits:

utilize favorable aspects of different habitats

for different life stages.

insect evolution2
Insect Evolution
  • Most advanced insect orders
    • Lepidoptera with 120,000 species
    • Coleoptera with 250,000 species
    • Hymenoptera with 89,000 species
    • Diptera with 78,000 species
the big four in review
The BIG Four [in review]
  • Origin of insects400 mya
  • Wings [paleopterous]350 mya
  • Wing flexion [neopterous]300 mya
  • Complete metamorphosis290 mya
slide30

“Humans are not the end result of predictable evolutionary progress, but rather a fortuitous cosmic afterthought, a tinytwig on the enormouslyarborescent bushof life.”--S.J. Gould, 1995

key points insect evolution1
Key PointsInsect Evolution
  • Evolution by Natural Selection
    • Survival of the Fittest
    • The 5 Principles
  • How is Paleoentomology important?
  • Evolutionary Timeframes
  • Important events in insect evolution