5.2 Scientific Contributions to the Theory of Evolution
2026-05-17 13:44
Status: #new
Scientific Contributions to the Theory of Evolution
Historical Briefing
Evolution as a theory
- A well supported explanation of phenomena that have occurred in the natural world
Beliefs before evolution
Creation - the idea of life being created by a deity or supernatural process
- Assumes life is unchanging and has always existed in its current state.
- Scientists were silenced and imprisoned for disputing creationism
The Evidence
- Fossils of species never seen alive were found
Notable People
Carl Linnaeus (1707-1778)
- Hypothesized that species came from hybridization and interbreeding of a handful of original species
George-Louis Leclerc, Comte de Buffon (1707-1788)
- Suggested that species change over time to create new organisms
- He theorized this as he saw similarities between humans and apes and believed there could be a common ancestor
Mary Anning (1799-1847)
- Discovered the first plesiosaur (aquatic reptile) fossil
Fossil Formation
Steps To Creating a Fossil
- Animal dies in a river
- The animal is covered in sendiment and is buried
- Over a long period of time, the bones are gradually chemically mineralized, while the flesh decomposes, giving way to our fossil. NOTE: flesh can be found in a fossil, but in extreme cases...
Layers of rock
- A layer of rock and soil sediment is known as the strata (plur. stratum)
Georges Cuvier (1769-1832)
- Credited for developing Paleontology (Study of ancient life through the examination of fossils)
- Every layer of rock is characterized by a unique group of fossil species
- The deeper the layer, the more dissimilar these species are
Destruction
- Proposed the earth experienced destructive natural events (Revolutions) periodically that killed numerous species every time (Catastrophism)
Catastrophism
- Drastic environmental events causing large population extinction events
Charles Lyell (1797-1875)
Aging of Earth and Geological Ideas
- The Earth was thought to 6000 years old; Lyell argues the earth is millions of years old
- This is since layers of rock take alot of time to form
Uniformitarianism
- Processes such as volcanoes and earthquakes shaped the earth and still occur today at the same rate
- Idea: Understanding the present helps us examine the past...
Jean-Baptiste Lamarck (1749-1829)
Theory of Acquired Characteristics
What is the theory?
- Organisms acquired traits by using their bodies in new ways.
- These new phenotype are passed to offspring as a process of adaptation.
- Within the lifetime of an organism, adaptations could occur
Why it is false
- Adaptations cannot occur in the lifespan of a organism. Instead it is a multigenerational process for adaptation to take place
Lamarck's Laws
Laws of Use and Disuse
- Usage of a trait leads to development, disuse of a trait leads to atrophy or disappearance
- Atrophy - Certain functions or structures diminish or disappear over time as they are no longer needed for survival in a particular environment
Used appendages were "better", unused were lost
Laws of Inheritance of Acquired Characteristic's
- New traits are passed onto offspring
Tendency Towards Perfection
- A innate tendency in living forces to drive them towards perfection
Why they are FALSE
Alfred-Russel Wallace (1823–1913)
- Proposed Natural Selection
- Wallace is known for the idea organisms being shaped by their environment
- Darwin is known for organisms shaped by competition for resources
How Wallace got ROBBED by Darwin (for developing evolution) >:(
- Less Known
Darwin published first - Wallace didn't use the word "evolution" in his publications
- At least naturalists and biologists today equally credit him with Darwin....
Charles Darwin (1809-1882)
Brief Overview
- Darwin enjoyed studying nature and had samples as a child
- While the son of physician, he opted for biology and became a naturalist
- While sailing on a scientific voyage on the HMS Beagle he observed different regions had structurally similar but distinct organisms...
- Begs the question Why are organisms clustered geographically?
- Fossils in a region shared characteristics of living organisms in that region
- Organisms in proximal regions share greater organisms characteristics
- In the Galapagos there was variation of finches between islands
- Given Artificial Selection (breeding) selected for heritable traits
- Begs the Idea: could the environment choose selection (Natural selection)
Darwins Theory of Evolution
Relation to natural selection
- Organisms more adapted to their environment are more likely to survive and pass on their genes that aided their success
1. Organisms differ within a species
- Variation is also inherited
2. Organisms produce more offspring to survive
- Those with traits that make them suitable to reproduce will survive
3. Organisms must compete for resources
- There is a limited amount of energy in a habitat
- Those who win in resource competition will LIVE
4. Advantages to survival can be inherited by offspring
- Genetics play the KEY role in evolution
- Evolution is a generational process taking a insurmountable amount of time
- Such that: Survival advantages depend on the environment
5. Descent with Modification
- All life comes from a common ancestor
- All species alive today are slowly modified versions of those ancestors