Plato and Aristotle
Believed that all life existed in a perfected and unchanging form
Georges-Louis Leclerc, Comte de Buffon
● Proposed that species could change over time
● These changes could lead to new organisms
Georges Cuvier
- Developed the science of paleontology (study of fossils)
- Found that each layer of rock had a unique group of fossil species
Charles Lyell
- Believed that slow, subtle processes could happen over a long period of time
- These could result in substantial changes
Jean-Baptiste Pierre Antoine de Monet Chevalier de Lamarck
- Presented the first theory of evolution
Lamarck’s Theory
- Believed that new, very simple species were continually created by spontaneous generation
- Believed characteristics that an organism acquired during its lifetime would be passed onto its offspring
Lamarckism = inheritance of acquired characteristics
Gradualism
slow, steady, linear change over time
Punctuated equilibrium
long periods of equilibrium interrupted by “rapid” periods of speciation
Speciation
formation of a new species through natural selection, driven by changes in the environment
Divergence
one or more species arise from a parent species that continues to exist
Adaptive Radiation
diversification of a common ancestral species into a variety of species, all of which are differently adapted
1) The Fossil Record
The sequence in which fossils appear matches the sequence in which they would be expected to evolve
What fossils demonstrate:
- Species living now are very different than those alive even 1 million years ago
- Fossil record shows the gradual progression of certain organisms from one form to another
- Complexity of organisms has increased over time
- Living species and their closely related fossils are located in same geographical region
Dating Fossils
- Radiometric dating is used to determine the age of fossils
Radiocarbon dating - Relative Dating – determines the sequential order of a series of events
- Index fossils – used to define and identify different geologic periods
2) Patterns of Distribution
●Species that are geographically isolated tend to demonstrate unique patterns of variation compared to species that are less isolated
● Closely related populations in similar geological ranges tend to demonstrate continuous variation, matching the concept of gradual divergence from a common ancestor
3) Comparative Anatomy
Species that are closely related tend to have a lot of structural similarities
* Similarities exist between different species that suggest common ancestor/origin
* Homologous structures
* Similar in origin (appearance)
* Therefore common ancestors
* but have different function/uses
The basic form is inherited and modified to suit the present function
Analogous features
similar in appearance and perform similar function, but don’t have
same evolutionary origin.
o Therefore different ancestors
o Normally such structures develop because of a common
environment
4) Embryology
demonstrates how tiny changes in protein signalling during development can result in large-scale anatomic change
5) Physiological Evidence
- Certain chemicals in organisms, as well as the function of these chemicals, are similar if not the same.
- Hormones: insulin in pigs and humans
- Thyroxin in frogs and humans
6) Biogeochemical Evidence
Biochemical Evidence - similarity in DNA sequences; this is now used to determine similarities and common ancestry
* Over time, the sequences of genes or proteins change, the GREATER the differences, the LESS closely related organisms are likely to be
