1. Evolution Notes
Chapter 10

2. Evolutionary Terms to Know
Evolution – change over time
Microevolution – small changes over time within a species
Macroevolution (AKA Speciation) – over time, groups of organisms change so much that they can no longer reproduce with the original group
Adaptation – trait that allows an organism to survive and reproduce
Variation – different traits of individuals

3. Evolutionary Terms to Know, cont’d
Competition – occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time
Species – group of organisms that either interbreed or have the potential to interbreed in a natural population; offspring are fertile
Fitness – ability of an individual to survive and reproduce in its environment

4. Creation
In the early 1800’s, most people believed that each species was created divinely a few thousand years before, and continued as it was originally created.

5. Voyage of The Beagle Charles Darwin Father of Evolutionary Theory
Made observations on a ship called the H.M.S. Beagle on a voyage to the Galapagos Islands in 1831.
Observations and collected evidences led him to propose a revolutionary hypothesis about the way life changes over time.

6. Voyage of The Beagle Darwin’s Observations
Plants and animals are well suited to environments
Organisms have many ways to survive and reproduce
Similar habitats in separate locations don’t always have the same animals
Fossils
Collected preserved remains and came up with questions like:
Why had these species disappeared?
How were they related to living organisms?
Galapagos Islands
The characteristics of many animals and plants varied noticeably among the different islands

7. Voyage of The Beagle The Voyage Home
Studied his collections in detail on the journey home
Because the characteristics of many plants and animals varied so greatly, he began to wonder if they had once been members of the same species
Hood Island Tortoise – long neck (sparse vegetation)
Isabela Island – short neck (vegetation close to the ground)
Pinta Island – intermediate neck (what does this say?)

8. Other Scientists and their Contributions
Geology and the Earth
James Hutton (1785)
Proposed that the Earth is shaped by geological forces that took place slowly over extremely long periods of time
Estimated that the Earth was millions, not thousands, of years old
Charles Lyell (1833)
The Principle of Geology – explained that processes like earthquakes, volcanic eruptions, erosion, weathering, etc. have shaped the Earth’s geologic features
Influences on Darwin:
If Earth could change over time, could organisms change as well?
For life to change, the Earth must be extremely old.

9. Other Scientists and their Contributions, cont’d
Jean-Baptiste Lamarck (1809)
By selective use or disuse of organs, organisms acquired or lost traits, passing them to offspring
Tendency Toward Perfection
Organisms change and acquire traits that help them live more successfully in their environments
Use and Disuse
Organisms alter the size or shape of certain organs by using their bodies in new ways
Inheritance of Acquired Traits
If organs are changed in some way, those changes are passed to offspring
Evaluating these thoughts
Didn’t know how traits were inherited
Didn’t know that behavior has no effect on heritable characteristics
One of the first scientists to develop a theory of evolution and realize that organisms adapt to their environment

10. Other Scientists and their Contributions, cont’d

11. Other Scientists and their Contributions, cont’d
Thomas Malthus (1798)
If the human population increases faster than the resources, there would be competition for food and living space.
Influences on Darwin
Competition certainly applies to animals and plants, since they produce many more offspring than humans

12. Other Scientists and their Contributions, cont’d
Alfred Wallace (1858)
Independently conceived the theory of natural selection
Wrote a short essay summarizing his thoughts on evolutionary changes, which encouraged Darwin to finally publish The Origin of Species (1859)
Other contributions:
Identifying the purpose of warning coloration in animals
“Wallace Effect:” natural selection could contribute to speciation by encouraging barriers against hybridization

13. Darwin’s Four Tenets (1865) Why does Natural Selection Occur?
Overproduction of Offspring
More organisms are made than the environment can support  competition
Genetic Variation
There is variation among offspring  preadaptation
Struggle for Existence
Natural Selection – survival of the fittest; the environment selects against traits
Climate, weather, competition, predators, pollution
How is this different from Artificial Selection?
Differential Survival and Reproduction
Individuals that have desirable traits are more fit and leave more offspring

14. What is Natural Selection?
The struggle for existence leads to survival of the fittest (natural selection).
The “fittest” are those with an inherited characteristic that makes that individual better suited to survive and be able to reproduce.
These characteristics are called adaptations.

15. What is Natural Selection? Cont’d.
Natural Selection results in changes in inherited characteristics of a population due to the environment, increasing the species’ fitness in that environment.
These changes are observed over long periods of time and throughout many generations

16. Descent with Modification
Principle of Common Descent:
All living things are related due to a common ancestor

17. Evidences for Evolution
Fossil Record
Provides evidence about the history of life on Earth
Shows how organisms have changed over time
Most form in sedimentary rock. Layers of sediment build up over time and dead organisms can be buried.
Trace Fossils – remnants such as footprints or waste
Body Fossils – body parts such as a bone or skull

18. Evidences for Evolution, cont’d
Fossils, cont’d
“Missing Links” – intermediate fossils between groups of organisms
THE FOSSIL RECORD IS NOT COMPLETE!

19. Evidences for Evolution, cont’d
Fossils, cont’d
Relative Dating – Allows paleontologists to estimate a fossil’s age by comparing it to other fossils. Based on the idea that older rock is found under newer rock. Does not provide exact ages, just estimates.
Younger layers
Older layers

20. Evidences for Evolution, cont’d
Fossils, cont’d
Radioactive Dating – Scientists calculate the age of a sample based on the amount of radioactive isotopes.
Carbon-14: is in all living things, but starts to decay immediately upon death
Carbon-12: is also in all living things, but does not decay
Scientists compare the ratios of these two elements to give an age of the fossil

21. Evidences of Evolution, cont’d
Homologous Structures
Structures that have different mature forms in different organisms but develop from the same embryonic tissues
Provides strong evidence that that all four-limbed vertebrates have descended, with modifications, from common ancestors

22. Evidences for Evolution, cont’d
Homologous Structures, cont’d
Analogous Structures – tissues that have the same function but the species are not necessarily related
Vestigial Structures – organ that no longer serves any useful purpose in an organism
EX: The leg bone present in pythons suggests that they once walked

23. Evidences for Evolution, cont’d

24. Evidences for Evolution, cont’d
Embryology
Vertebrates have similar embryos
Must mean that there are similar genes at work
Similar genes indicate a common ancestry
Differences in development are caused by genes that have mutated during the course of evolution

25. Evidences for Evolution, cont’d
Embryology, cont’d

26. Evidences for Evolution, cont’d
Biochemistry/Amino Acid Sequences
The more similar two organisms are, the more similar their DNA is.
This indicates that certain organisms have evolved from a common ancestor
EX: conserved sequences in DNA, Hemoglobin, etc.

27. Evidences for Evolution, cont’d
Biogeography/Geographic Distribution of Living Species
Species evolve differently in different environments
Darwin discovered that the little brown birds he collected on his trip to the Galapagos islands were all finches; however, they were all distinctly different
Determined that the finches had a common ancestor and descended with modification to their individual environments