How the Theory of Evolution was Formed
Jean Baptiste Lamarck
Use and
Disuse
Theory of Acquired
Characteristics
• Species evolve over time
• Species evolve to become better adapted to their environment
• Changes are passed on from generation to generation
**it is the mechanism that still needed to be explained**
Scientists that Contributed to our present Theory of Evolution
• Species evolve over time
• Species evolve to become better adapted to their environment
• Changes are passed down from generation to generation
Georges Cuvier
• Species evolved from simple to more complex
Catastrophism
Scientists that Contributed to our present Theory of Evolution
• Species evolve over time
• Species evolve to become better adapted to their environment
• Changes are passed down from generation to generation
• Species evolved from simple to more complex
Charles Lyell
Uniformitarianism • Geological change is
slow and gradual – and therefore so was evolutionary change
Speciation Dynamics - Gradualism or Punctuated Equilibrium?
The theory of gradualism states that as new species evolve, they appear very similar to the original species and only gradually become more distinctive
e.g. Whales and Horses
The theory of punctuated equilibrium suggests that the process of evolution is slow, but is occasionally punctuated by periods of rapid change
e.g. Hawaiian Honeycreepers
This theory explains the lack of fossils of transitional species due to the fact that speciation usually occurs small isolated populations
It is now widely accepted that both play a significant role in evolution.
Two Patterns of Speciation
So Does Evolution Create the Perfect Organism?
No, only better organisms as evolution is constrained by history and buffeted by random events.
Essentially, every organism on earth is in significant part a sum of accidents.
Evidence for Evolution Biogeography Homologous and Analogous features Embryology Vestigial features Competition within Populations
What set apart Darwin’s theory from other scientists’ was that it explained how species had evolved, using amassed evidence.
7.3 Darwin’s Voyage on the HMS Beagle Biogeography evidence for evolution
Biogeography Geographic patterns of distribution Fossil evidence suggest that ancestral
species evolved separately once the supercontinent, Pangaea, separated.
Endemic species evolved a lack fear of predation
Red colobus monkey (endemic
to Zanzibar, Tanzania
Homologous Structure/Feature
Similar structures found on different species that have entirely different functions.
E.g. Same (but modified) bones and relative positions
Embryology
The embryos of all vertebrates,including humans, chickens, and fish, share a similar pattern in development Provides evidence of
evolutionary relationships between species
Analogous Structure/ Feature Structures in different species with the same appearance,
structure, or function but have evolved separately, thus do not share a common ancestor. E.g. wings of insects and birds used for flying
E.g. fins of fish and flippers of whales used for swimming
Vestigial Features
Physical features that exist with no practical function
Competition WITHIN Populations A limiting factor to survival is always FOOD SUPPLY All species produce more offspring than can survive to
reproduction This results in a competition for resources, especially when the
number of individuals exceeds the amount that can be supported by the habitat.
Modern Evidences of Evolution
Pseudogenes Homologous Genes Plate tectonics Paleontology
How does evolution occur?
Core principle:
BeneficialNeutral MutationsHarmful
Genetic Variation in a Population
Selection Pressure
Evolution of a Species
• Natural Disaster• Mate Selection• Climate Change• Artificial Selection
How might it be possible for a neutral mutation to play an important role in the evolution of a species?
