1. The Development of Evolutionary Theory
Chapter 2
The Development of Evolutionary Theory

2. Chapter Outline Brief History of Evolutionary Thought
Natural Selection in Action
Constraints on Nineteenth-Century Evolutionary Theory
Opposition to Evolution

3. Evolution A change in the genetic structure of a population.
Also refers to the appearance of a new species.
Often controversial, some religious views hold that evolutionary statements run counter to biblical teachings.

4. Evolution Is a Theory
The theory has been supported by a mounting body of genetic evidence.
The theory has stood the test of time.
The theory stands today as the most fundamental unifying force in biological science.

5. Pre-scientific View
In the middle ages, the predominant world was stasis, the world was fixed and unchanging.
The great chain of being held that life was arranged from simplest to most complex.
It was believed that the earth was “full” and nothing new could be added.
The world was seen as the result of a grand design - God’s design.

6. The Scientific Revolution
Discovery of the new world challenged fundamental views about the planet.
Exposure to new plants and animals increased awareness of biological diversity.

7. The Scientific Revolution
Copernicus challenged the idea that the earth was the center of the universe.
Galileo’s work supported the idea that the universe was a place of motion.
Keppler, Descartes and Newton established the laws of physics, motion and gravity.

8. Precursors to the Theory of Evolution
John Ray provided first definition of the concept of species and genus.
Carolus Linnaeus developed system of classification and the basis for taxonomy.
Comte de Buffon stressed the importance of change in the universe and the environment as an agent of change.

9. Precursors to the Theory of Evolution
John Baptiste Lamack was the first scientist to produce an explanation for the evolutionary process.
Georges Cuvier introduced the concept of extinction and the theory of catastrophism.
Charles Lyell developed the theory of uniformitarianism.
Thomas Malthus wrote about relationship between food supply and population increase.

10. Charles Darwin ( )
Ideas were formed while serving as a naturalist on the voyage of the HMS beagle.
Darwin saw the importance of biological variation within a species.
Recognized the importance of sexual reproduction in increasing variation.
By 1844, Darwin had complete the work that he would publish fifteen years later.

11. The Path of the HMS Beagle

12. Alfred Russell Wallace (1823-1913)
A naturalist who worked in South America and Southeast Asia.
Suggested species descended from other species and new species were influenced by environmental factors.
Presented paper on evolution and natural selection to the Linnean Society of London jointly with Darwin.

13. Contrasting Views on Evolution

14. Contrasting Views on Evolution

15. Processes of Natural Selection
Species can produce offspring at a faster rate than food supplies increase.
There is biological variation within all species.
In each generation, more individuals are produced than can survive.

16. Processes of Natural Selection
Individuals that possess favorable traits or variations are more likely to survive and produce offspring.
Environmental context determines whether a trait is beneficial.
Traits are inherited and passed on to the next generation.

17. Processes of Natural Selection
Variations accumulate over long periods of time, so later generations may be distinct from ancestral ones.
As populations respond to pressures over time, they may become distinct species, descended from a common ancestor.

18. Evolutionary Change Through Natural Selection
A trait must be inherited if natural selection is to act on it.
Natural selection can’t occur without population variation in inherited characteristics.
Fitness is a relative measure that changes as the environment changes.
Natural selection can only act on traits that affect reproduction.

19. Quick Quiz

20. 1. To understand the complexities of evolution one must be well versed in
mathematics and statistics.
botany and paleontology.
genetics and biology.
anatomy and physiology.

21. Answer: c
To understand the complexities of evolution one must be well versed in genetics and biology.

22. 2. Genetic evidence supports evolution.
True
False

23. Answer: true
Genetic evidence supports evolution

24. 3. Darwin realized that variation among _________________ was how selection occurred, ultimately causing change in species.

25. Answer: individuals
Darwin realized that variation among individuals was how selection occurred, ultimately causing change in species

26. 5. Natural selection acts on existing _________________ within a species.

27. Answer: variation
Natural selection acts on existing variation within a species.