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E volution Thursday 10/24/13. Charles Darwin influences on his thinking // decent with modification evolution by natural selection overview Evidence of Evolution fossil record biogeography comparative anatomy // embryology molecular biology

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slide1

Evolution Thursday 10/24/13

  • Charles Darwin
    • influences on his thinking // decent with modification
  • evolution by natural selection
    • overview
  • Evidence of Evolution
    • fossil record
    • biogeography
    • comparative anatomy // embryology
    • molecular biology
    • studies demonstrating evolution
slide2

Evolution:

  • change
  • change in
  • change in
  • Charles Darwin – “father of evolution” proposed a mechanism of change over time…….
slide3

Historical Context

  • Prevailing thought prior to Darwin’s time:
  • Darwin was strongly influenced by the writings of geologist Charles Lyell
    • Lyell proposed
    • earth was at
  • Darwin reasoned that:
    • IfEarth is
    • then subtle processes occurring
slide4

Historical Context

  • Malthus’“Essay on the Principle of Population”(published 1798)
  • Darwin was strongly influenced by the Malthus’ writings and reasoned that:
    • all though all organism
    • only a limited number
slide5

The Voyage of the Beagle

  • In December 1831, Darwin left Great Britain on the HMS Beagle to explore the world…..

Darwin’s voyage on HMS Beagle 1831-1836

see fig 27.1

slide6

Darwin was intrigued by:

  • Fossil beds of South America
  • Species composition
  • Plants and animals on
  • Yet, species in similar habitats
  • Similar species
slide7

Theory of Evolution by Natural Selection:

Based on observations during his travels and subsequent research/experimentation, Darwin proposed a theory to explain how and why populations change over time:

Wrote manuscript – “Origin of Species” in 1844 – not published until 1858

w/in a decade - widely accept that evolution occurs

Fig 27.3

slide8

Descent with Modification

Darwin made two main points in The Origin of Species:

  • Organisms inhabiting Earth today
    • not all individuals
    • individuals best fit
    • population becomes
slide9

The result of natural selection is evolutionary adaptation:

(b) A Trinidad tree mantid that mimics dead leaves

(a) A flower mantid in Malaysia

(c) A leaf mantid in Costa Rica

slide10

Evolution:

  • Darwin did not invent the idea of evolution; he agreed with many philosophers and naturalists that diversity was produced by evolution
  • But scientists did not know how evolution occurred: prior to Darwin there
  • A predecessor to Darwin,
slide11

Adaptations / Evolution:

  • Lamarck’s theory of acquired characteristics
    • individuals passed on
    • better variations

fig 27.2

slide12

Adaptations / Evolution:

  • Darwin’s theory
    • parents with
    • frequency of adaptive traits
slide13

Descent with modification:

Think about “artificial selection”

  • In Nature -- NATURE DOES

Figure 13.5

slide14

Evidence of Evolution

  • Grant’s work & the Darwin’s Finches
slide15

Rivers bring sediment to the ocean. Sedimentary rocks containing fossils form on the ocean floor.

1

Over time, additional strata are added, containing fossils from each time period.

2

3

As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion by rivers reveals strata; deeper strata contain older fossils.

Younger stratum with more recent fossils

Older stratum with older fossils

Fossils

  • preserved
  • often found in
slide16

The fossil record

  • the
  • testifies that

present day South American armadillo

extinct - found in fossil record

slide17

Fossil Record & Transitional species:

  • examples:
    • fish --> early tetrapod --> modern tetrapod (amphibians)
    • early whales --> modern whales
slide18

Biogeography

  • the study of the
  • suggested to Darwin that
  • organisms in
  • organisms on isolated islands

Australia

Koala

Kangaroo

slide19

Comparative Anatomy

see fig 27.7

    • the comparison of
    • confirms that
  • Homologous characters
  • Analogous characters
slide20

Comparative Embryology

  • Comparative Embryology is the comparison of structures

see fig 27.8

Comparative embryology of vertebrates supports evolutionary theory

-

slide21

Molecular Biology

  • Evolutionary relationships among species
  • more closely related evolutionarily:
  • more distantly related evolutionarily:

relative similarity between CytochromeC structure (protein used in ETC)

fig 27.9

slide22

Evidence of Evolution

  • Example of microevolution:
    • Darwin’s finches - medium ground finch

Peter and Rosemary Grant

Researchers at Princeton, began studying the finches in the 70’s

Geospiza fortis –

Medium Ground Finch

darwin s finches
Darwin’s finches

South America

  • Grassquit colonized islands from SA 2.3 mya
  • Darwin observed on Beagle 1831-1836

Galapagos

  • noticed: different bills and diets
slide25

Researchers captured, measured, weighed, and banded individuals

Medium Ground Finch

Variation in

  • Variation in
slide26

variation in

    • population of

Over 20 months 84% disappeared before breeding

slide27

Selective pressure:

  • Typically
  • Number and type of seeds

Tribulus seeds

result evolution of greater beak depth
Result: evolution of greater beak depth
  • mean beak depth of finches hatched in 1976:
  • mean beak depth of finches hatched in 1978:
  • fossils:
slide29

heritable character!

Evidence of Evolution

  • Example of microevolution: change w/in a population over generations
  • variation in
    • larger bill -
    • smaller bill -
  • weather conditions
  • selective advantage
  • large-billed birds

fig 22.12

see fig 27.11

slide30

Evolution of Pesticide- Resistant Insects

  • variation in population
  • differential survival
  • change in frequency of

Note:

slide31

Evolution at level of POPULATION not individual!

  • insects had gene or did not have gene
    • w/ gene -
    • w/o gene -
    • change in
  • subsequent generations
slide32

Adaptations -- Individuals vs. Population:

  • populations adapt
    • variation in the
    • what is “adaptive”
  • individuals are adapted
    • individuals with
slide33

Evolution by Natural Selection: summary

  • historical thinking ripe for Darwin’s theory
  • evolution occurs at the
    • changes in frequency
    • constrained by ancestry
  • variety of evidence supports the theory of evolution
    • one mechanism
      • passing down
      • increase probability
    • KEY aspect of