Welcome to Evolution

Biol 4208

Lecture 1, Chapter 1


Dr. Julie R. Etterson


Two objectives for today

  1. General introduction to the course
  2. Overview of the syllabus


The earth is incredibly diverse

  1. True at all levels of biological organization
  2. Biomes
  3. Communities within biomes
  4. Species within communities
  5. Populations of a given species
  6. Physiological tolerances
  7. Nutritional requirements
  8. Life span
  9. Reproductive system
  10. Capacity for behavior
  11. Gene sequences of an individual
  12. Catalytic abilities of enzymes
  13. Structure of cells and organisms

People have struggled to understand earth’s complexity

  1. Where did living things come from?
  2. Why are there so many different kinds?
  3. Why are they so apparently well-designed for living where they live?
  4. Why are they so apparently well structured for doing what they do?
  5. Most cultures of the world have creation stories

a)     Genesis

b)     Native American

c)      African

Western scientific thought on creation

  1. Essentialism

a)     Originated with Plato and Aristotle

b)     Every form and idea has a perfect immutable essence that is imperfectly imitated on earth

c)      Creation follows “Great Chain of Being” that grades from inanimate objects to lower forms of life (i.e. bacteria, plants, insects) to the higher forms of life.

d)     Because humans are both physical and spiritual, we are a link between animals and angels.

  1. The Great Chain of Being

a)     The chain of being, from Charles Bonnet, Œuvres d'histoire naturelle et de philosophie, 1779-83

  1. Until the 18th century, the role of science was to catalogue nature to appreciate the wisdom of the creator

a)     Exhaustive categorization of plants and animals in Systema Naturae (1735) was undertaken to discover the pattern of creation

b)     “Relatedness” meant closeness to the Creator’s design

  1. Uniformitarianism

a)     New theories emerged for origin of the stars and planets

b)     Evidence was found that the Earth had undergone extensive changes over time

c)      Evidence of extinct species was found by geologists

d)     New theory was proposed that the same processes that have happened in the past are continuing to happen in the present

  1. First coherent theory of evolution

a)     Each species arose from nonliving mater by spontaneous generation

b)     “nervous fluid” causes progress up the “Great Chain of Being” according to inner needs

c)      Acquired characteristics are inherited

Figure 1.3A (1,2)  - Lamark’s Theory

Figure 1.4 (1,2) - Transformational vs. variational evolution

Species differ for two reasons:

1.       different ages

2.       different needs

Darwin’s inspiration

  1. Trained as clergyman but passionately interested in natural history
  2. Invited to be a naturalist on 5-year voyage on British naval ship, the Beagle, charting South American waters
  3. Galapagos island collections particularly important
  4. Collected enormous numbers plants and animals
  5. Ornithologist examining his collections pointed out similarities and differences between mainland and island races
  6. Birds on islands shared a common ancestor
  7. Species that arrived from the mainland had diverged into many forms
  8. Differences in tortoises on different islands also observed

Figure 1.3B – Darwin’s theory(1,2)

Darwin’s theory of variational evolution

  1. Species diverged from one family tree
  2. Characters of lineages change over time
  3. Radical change results from many generations of gradual and incremental change
  4. Evolution occurs by changing the proportion of individuals with certain characteristics within populations
  5. Proportions change because certain characteristics allow greater survival and/or reproduction of individuals that expression them
  6. One very serious problem Darwin could not address.
  7. Mechanism of inheritance
  8. Prevailing idea of blending inheritance didn’t work
  9. All individual become more alike over time
  10. Amassed evidence for evolution for 20 years until Wallace sent him a manuscript outlining the theory of natural selection

Is evolution a theory, a hypothesis, or a fact?

  1. “Theory” in everyday language means unsupported speculation
  2. A scientific theory is coherent body of interconnected statements based on reasoning and evidence that explain a variety of observations
  3. A hypothesis is an informed statement of what might be true
  4. A strongly supported hypothesis is considered a fact
  5. A fact is something that we observe to be true
  6. Most “truths” cannot be proven

What is a scientific truth?

1.      Plate tectonics was a new theory when I was a kid

2.      Extensive support has accumulated in the last decades

3.      Considered a scientific fact

4.      New ideas refine the theory

5.      Novel that explores mathematical truths and great existential questions

6.      Follows the lives of two 20th century mathematicians, Turing & Gödel

7.      1931 "incompleteness theorems"

8.      Some mathematical truths can never be proven

9.      Unsettling scientific and human implications

10. Posited hard limits to what we can ever logically, definitively know

What constitutes evidence in evolution?

1.      Form a hypothesis based on observation

2.      Make a prediction based on theory

3.      Test the hypothesis in an experiment

Compelling evidence supports the theory of evolution to the extent that it is consider “fact” by most scientists

Evolution of antibiotic resistance

  1. 25-30% people are colonized without adverse effects
  2. Originally all susceptible to penicillin
  3. 50 % resistant to stronger drug, Methicillin
  4. Vanocomycin that was used to treat methicillin-resistant hospital strains - now resistant
  5. MRSA more prevalent in hospitals

Figure 1.2 – Drug resistance

Evidence in Evolutionary Biology

  1. Where do guppies originate?
    1. Tropical streams

Evolutionary thinking

  1. Make one or more observations (facts)
  2. Develop a hypothesis to explain the pattern your observe
  3. Think of experiments to distinguish between your hypothesis and the null hypothesis
  4. Evaluate which hypothesis is supported by your data
  5. Guppy coloration differs in different ponds
  6. Guppies cannot cross waterfalls