Evolution: History & Process (Chapter Development of a Theory Evolution

1. Evolution is a change in the hereditary features of a population over time
Adaptations are traits that make organisms better able to survive
Mutations are the source for new traits
Ideas of the Time
1. Georges Buffon suggested:
The Earth is much more than 10,000 years old
Fossils were similar and different to living animals
2. Jean Baptiste Lamark proposed inheritance of acquired characteristics
Giraffe necks lengthen by stretching over time
Mistaken explanation
The Voyage of Charles Darwin
1. Charles Darwin voyaged around the world on the HMS Beagle
Gathered plant and animal specimens
Made observations on the Galapagos Islands
Read about gradual geological processes that shape the Earth
2. Wrote The Origin of Species which explained his “theory of evolution”
Natural Selection
The Origin of Species
1. Descent with modification
Organisms living today descended from ancestors
They accumulated modifications to diverse ways of life
2. Natural selection: something in the environment determines if an organism will survive to have offspring
Overproduction- more organisms are produced than can survive
Variation- different traits found in a population
Completion- struggle to survive, compete over resources
“Survival of the fittest”- only the strongest survive, mate, and produce offspring with string traits
Speciation- evolution of species with adaptations
Artificial Selection
1. Artificial Selection: humans determine if an organism will survive to have offspring
selective breeding of domesticated plants and animals
Selection in Action

1. Natural selection and evolution can be observable events
   Pesticide resistance in insects
   The peppered moth on Manchester
   Evidence of Evolution
   Geological Evidence

2. Fossils
   Preserved remain of once living organisms (extinct)
   footprint, leaf imprint, bones, insect in sap
   2. Sedimentary rock
   Forms from layers of mud, sand, other, small particles
   Fossils form in these layers
   Oldest in bottom layers, youngest in top layer
   Selection

3. Similarities in development
   Comparison of embryos
   Many animal embryos look very similar
   2. Comparison of DNA
   All organisms have DNA
   More similar organisms have more similar DNA
   3. Comparison of structures
   Homologous- similar in structure
   Inherited from a common ancestor
   Example: arm of human and cat
   Analogous- similar in function
   Not inherited from a common ancestor
   Example: wing of butterfly and bird
   Vestigial- no longer has a function
   Inherited from an ancestor
   Examples: appendix of human, wings of an ostrich
   Mechanisms of Selection
   Hardy- Weinberg’s Gene Pool

   1. A gene pool consists of all the alleles of all the individuals in a population

4. Microevolution is a change in a population’s gene pool

5. Hardy- Weinberg equilibrium: no change in gene pool = no evolution

6. Changes in population can arise by:
   Genetic drift
   Gene flow
   Nonrandom mating
   Mutation
   Natural Selection
   Genetic Drift

   1. Genetic drift is a change that occurs by chance in a small gene pool
      Bottleneck effect- a disaster (fire) leaves only a few to reproduce
      Founder effect- a few individuals colonize an isolated area (island)
      Gene Flow & Mutation
   2. Gene flow is due to migration of fertile individuals into or out of a population
   3. Nonrandom mating includes inbreeding and the selection of mates with specific phenotypes

7. A mutation is a random change in an organism’s DNA that creates a new allele
   The original source of variation
   The Evolution of Health
   Evolution of Sickle Cell

   1. Sickle cell affects 1 in 25 in parts of Africa
      Suffer pain, organ damage even death

8. Individuals with one copy of the gene (32%) are resistant to malaria
   Antibiotic Resistant Bacteria

   1. Antibiotic kill or slow the growth of bacteria
   2. Resistant to antibiotics evolves by natural selection
      Tuberculosis (TB)
   3. We must prevent overuse of these drugs