Bio Notes

C1.1 - Evolutionary Theory

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C1.1 - Evolutionary Theory

Evolutionary Theory

Image of Tiktalik, fish-like organism found in Northern Canada

Tiktalik fossil and recreation
  • All life forms are fundamentally similar at a cellular and molecular level
  • Evolution explains life history on Earth
  • Evolution is the process where organisms change over time
  • evolution: theory that all species are descendants of ancient species differing from modern-day species

Theory vs. Hypothesis

  • theory: set of statements that explain a group or phenonema
  • hypothesis: suggested explanation of observations, that can be tested by further research or experiments

Early Theories

  • Acceptance of evolutionary theory not universal
  • Geological time not understood
  • Archbishop James Ussher through the Bible, Torah, and other religious books researched age of Earth
  • Ussher’s age of Earth: 4004 BCE — Earth is 6,000 years old
  • Living things thought to be immutable (unchanging)

History of Geological Theories

  • Humans are the only species to know their times are limited
    • Driven humans to find an escape to death
  • Religion offers time w/o end, place to go after death
  • Christians are told they’re immortal, death is a phase
  • Around 1650, James Ussher using religious books like the Bible, Genesis and the Torah determines beginning of time: 4004 BCE
  • James Hutton challenged 6000-year-old history by looking at geological evidence
    • i.e. the Grand Canyon in Arizona — Colorado river flows btwn. 2 states
    • River digs canyon 1 ft. deep / 1000 years through erosion
    • est. 5.5 million years to make canyon
    • Erosion revealed layer of time, layer deposited 1 in. / 1000 yrs
    • 6 in. of canyon = 6000 years
    • Hutton realized that Earth is older than 5.5 million years

Theories Leading to Evolutionary Theory

Uniformitarianism — James Hutton

  • uniformitarianism: theory that states the Earth was formed entirely through slow-moving processes like erosion and sedimentation, and that these processes continue to shape the Earth today
  • Proposed by James Hutton, Scottish geologist
  • Molten material is forced up to Earth’s surface to form rock
  • Rock is then eroded away
  • Sediment from erosion washed into the sea and eventually compacts to form sedimentary rock
  • erosion: removal of surface material (i.e. rocks) through natural forces (i.e. water, wind)
  • sedimentation: accumulation or depositon of sediments (small fragments) that compact to form a new structure

Principles of Geology — Charles Lyell

  • Written by Charles Lyell, English geologist
  • Popularized and expanded on Hutton’s theory of uniformitarianism
  • Found more evidence to support that rocks were formed through slow-moving processes

Use and Disuse Theory — Jean-Baptiste Lamarck + adaptation

  • adaptation: inherited characteristic that improves an organism’s ability to survive and reproduce in a particular environment
  • Proposed by Jean-Baptiste Lamarck, French naturalist around the 1800s

GUIDING IDEAS

  1. By using or not using certain body parts, an organism develops certain traits
    1. i.e. giraffes developed long necks because they needed to reach food in tall trees
  2. inheritance of acquired characteristics: Enhanced developed characteristics will be passed down to that species’s offspring
  3. tendency toward perfection: Organisms continuously change and acquire features in order to be more successful in their environments

Theory Proven False

  • Acquired characteristic would somehow have to change the DNA of specific genes in order to be inherited
  • NO evidence of this happening
  • Important in analyzing role of environment and explaining evolution as a process of environmental adaption

Histoire naturelle, générale et particulière — Georges-Louis Leclerc, count de Buffon

  • Buffon did comprehensive work on natural history through his book Histoire naturelle, générale et particulière (1749-1804)
  • Produced an account of the whole of nature
  • First modern attempt to systematically present all existing knowledge on natural history, geology and anthropology in one book

Evidence

  • Earth is old (~4 bil years old), made from destroyed stars
  • Radiometric dating, caused by energy/particles being given off by nuclei (radiation)
    • Akasta, NWT — 4 billion year old rock escaped being recycle
  • Analysis of fossil record
    • fossil: when bone or tissue turn into rock
    • Leonardo DaVinci lived in Tuscany and walked in Italian moutain ranges
    • Found seashell fossils in mountain ranges
    • Evidence for tectonic plate movement — they push and make the land rise
  • Vestigial organs: organs that had a use in the past but not anyomore
    • i.e. goosebumps or appendix [questionable] in humans
  • Comparative Development
    • Embryology: study of development
    • All vertabrates have a stage where pharyngenal pouches appear on the side of the throat
  • Geographic distribution of species
    • How did frogs get from Africa to South America if they die in salt water?
  • Chromosomal analysis
    • Chimpansees have 47 chromosones while we have 46
  • Molecular analysis and biology
    • Chemical processes of cells are similar or the same
    • Amino acids that differ in human and gorilla hemoglobin is only 1 in a chain of 146 acids

Specific Examples

  • Changes in Beak Shape
    • In medium ground finches, beak size increases during dry years
    • In “wet” years, beak size decreases for abundant vegetation
  • Antibiotic Resistance in Bacteria
    • Tubercolosis (TB) bacteria was treated using an antibiotic (drug) called Streptomycin, developed in the 1940s
    • 1970s: TB almost completely wiped out
    • 2006: Outbreak of extremely resistant strain of TB in KwaZulu-Natal, South Africa
    • 2009: WHO reports that 1/3 of world population has TB
    • Some TB bacteria developed resistance to their antibiotics and they survived
    • These antibiotic-resistant bacteria reproduced and spread

Geographic Distribution of Species

  • Finches that Darwin found were all descendants of a single ancestral species from South American mainland
  • Finches became geographically isolated and developed characteristics best suited for their particular environment
    • i.e. beak shape and size

Similar selection pressures of species in geographically diff. areas forced them to develop similar traits

Fossil Record

Image of a fossil

Fossil
  • fossil: preserved remains of organisms turned into minerals
  • Organisms die and become trapped in sediments
  • Fossilization is very rare; requires water and no disturbance
  • Fossil record is incomplete

Types of Fossils

  • body fossil: fossil that preserves the remains of a former organism
  • molds: imprint left by remains of organism in rock/clay
    • external mold: mold outside of remains
    • internal mold: mold inside of remains
  • cast fossil: replica of an organism formed by molds
  • trace fossil: fossil that preserves the activities of a former organism
    • i.e. dinosaur footprints, ancient worm burrows

Palaeontology — Georges Cuvier

  • palaeontology: study of fossils
  • Shallower depositos reveal organisms most similar to those alive today
  • Relative age of fossils determined by French zoologist Georges Cuvier
    • Wrote Tableau élémentaire de l’histoire naturelle des animaux in 1797
    • Leçons d’anatomie comparée (1800-05)
    • Disagreed w/ viewpoints of Lamarck
  • Catastrophism responsible for extinction events

Radioactive Decay

Radioactive decay diagram
  • Allows absolute age of rock to be determined
  • Ratiometric dating used to measure amount of daughter isotope in sample
  • Decay constant over time
  • Carbon-14 testing used for more recent organic remains

Beginnings of Evolutionary Thinking

  • James Hutton proposes that geological change occurs over long period of time
  • Charles Lyell writes Principles of Geology
  • uniformitarianism states that Earth continues to change through gradual, uniform processes

Sources

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