Evolution: The process of biological change by which descendents come to differ from their ancestors
Principles of Evolution
Evidence of Evolution
Early Ideas about Evolution
Fossils
Geography
Early scientists proposed ideas about evolution
Different ecosystems favor different traits and can establish separate populations that have a common ancestor.
Biogeography: The study of the distribution of organisms around the world
More primitive fossil organisms are in older layers, with more complex forms found in upper layers
Georges Cuvier
James Hutton
Erasmus Darwin
Carolus Linnaeus
- Worked in the late 1700s
- Did not think that species could change
- Did believe that species could become extinct
- Proposed the theory of catastrophism
- Worked in the 1700s.
- Organized plants, animals and minerals into groups based on similarities
- Developed a classification system for organism
- Proposed that species can change over time.
- Late 1700s
- Proposed that landforms change over a long period of time
- Proposed gradualism
- Born in 1731.
- Argued that all living things were descended from a common ancestor.
- More-complex forms of life arose from less-complex forms.
Evidence for evolution in Darwin’s time came from several sources.
Catastrophism
Gradualism
The Earth's landforms are shaped by gradual processes, such as river and wind, over a long period of time.
Natural disasters, such as floods and volcanoes have happened in the past, shaping the landforms and causing species to become extinct. New species move into an area after a catastrophic event.
Uniformitarianism
Geological processes that shape the Earth are uniform throughout time. This theory combines. This theory strongly influenced Charles Darwin.
Georges Louis Leclerc de Buffon
Jean-Baptiste Lamarck
Anatomy
Embryology
Charles Lyell
Think: Same origin, different function
Think: Same function, different origin
- Worked in the 1700s.
- Suggested that species shared ancestors.
- Rejected the idea that the earth was 6000 years old.
- Worked in early 1800s
- Proposed that changes in physical characteristics could be inherited and were driven by environmental changes over time.
Vestigial Structures: remnants of organs or structures that had a function in earlier ancestors
Embryos of very different organisms that develop similarly provide evidence of a common ancestor
- Published Principles of Geology in 1830s
- Suggested that geological processes are uniform over time
- Proposed uniformitarianism
Many modern whale species have vestigial pelvic and leg bones. What does this suggest about the ancestry of modern whales?
The ancestor of whales lived on land - more on this at UM!
In the 1700s, many people believed that species were fixed and did not change. How did plant hybridization—a type of crossing that could be observed in experiments—help change this view?
What two conditions must be true for a group of animals to be considered the same species?
Lamarck’s ideas of evolution are known as the inheritance of acquired characteristics. What was incorrect about his theory of how organisms evolve?
Hybridization could produce different species, showing that a species can change
- They must be able to produce viable offspring
- They must be able to reproduce
Lamarck thought that an organism's use or disuse of an organ or structure would cause changes that would be inherited by it's offspring
Darwin's Observations
Theory of Natural Selection
Artificial Selection: The process of breeding a species for specific traits
Natural Selection: Mechanism by which individuals that have inherited beneficial adaptations produce more offspring than those who have not.
Darwin noticed breeders could produce a great amount of diversity in species.
If a trait is not heritable, it won’t be passed down to offspring.
The Grants
Why must selected traits be heritable?
Why did artificial selection interest Darwin?
In natural selection, what must be true of traits that are passed down through generations?
After several years, the supply of large seeds went down after an unusually wet period. The increase in small, soft seeds brought a(n) DECREASE in the number of large-beaked hatchlings the following year.
Peter and Rosemary Grant observed natural selection acting on traits within a population of finches on the Galápagos Islands. A drought reduced the number of small, soft seeds but left plenty of large, tough-shelled seeds intact. The next year there was a(n) INCREASE in the number of large-beaked hatchlings.
Heritability: the ability of a trait to be passed down from one generation to the next.
They must give an advantage in the organism's present environment.
What important idea from Thomas Malthus inspired Darwin?
But First! Something else you should be familiar with, so take notes in your SG!
Nucleotide/Amino Acid Sequencing and Molecular Fingerprinting
Human populations would grow geometrically if resources were unlimited. Instead, disease and a limited food supply kept the population smaller.
Four main principles of Natural Selection
- We can also use DNA to show relationships between species.
- All these organisms have hemoglobin, which carries oxygen.
- Over time, the amino acid sequence changes due to random mutations.
- The fewer the differences, the more related the two organisms are.
Population: all the individuals of a species that live in an area
Variation: Heritable differences in populations
Overproduction: More offspring results in competition for resources.
Fitness: measure of the ability of an organism to survive and produce more offspring in comparison with other members of the population in a given environment.
Adaptation: Variation that is beneficial for survival of an organism.
Descent with modification: Over time, adaptations will be well suited to survival and reproduction in an environment.
Adaptation: A feature that allows an organism to survive better in its environment
What island chain in South America was the source of many of Darwin’s insights?
Variation: Differences in physical traits of an individual from the group in which it belongs
Darwin observed fossils of huge animals such as Glyptodon, a giant armadillo. Why were these fossils of interest to him?
Darwin saw populations of various species that seemed well-suited to their environment. What did this suggest?
The Galapagos Islands
Intra-specific variation occurs among members of the same species.
Inter-specific variation occurs among members of different species
A species must be able to adapt to its environment.
He thought that modern species might have some sort of relationship to the fossil species
Look at Figure 2.2 in your textbook. What differences between the two Galápagos tortoises can you identify from the two pictures?
Darwin also observed fossil shells of marine organisms high up in the Andes mountains, and saw an earthquake move land that was underwater above sea level. How did he apply these insights to the evolution of organisms?
Many people in the 1700s thought that Earth was only about 6000 years old. How did the fossil organisms Darwin saw lead him to think Earth must be much older than that?
In order to account for all of the changes he observed between the fossils and modern species, it would take much longer than 6000 years.
He saw that great geological changes occur very slowly over time. He extended this idea to organisms.