1. Chapter 17
Evidence of Evolution
AP Biology
Spring 2011

2. Darwin Revolution
Traditional belief that Earth was only a few thousand years old and was populated by forms of life that had been created at the beginning and remained unchanged

3. Darwin Revolution
Aristotle: trying to categorize and organize living things
Chain of Being: organized life from lower to higher forms
Comparative Morphology: focused on revealing similarities and differences in body plans and structure of organisms

4. Darwin Revolution
Cuvier: suggested that abrupt changes in the fossil record in different rock strata reflected the concept of catastrophism
Catastrophism: dramatic geological changes unlike what we see today, after each catastrophe fewer species remained

5. Darwin Revolution
Jean-Baptiste de Lamarck: developed an early theory of evolution, which in part stated that characteristics acquired during an organisms lifetime could be passed on to the next generation
Modern understanding of genetics provides no evidence that this is possible!!
Giraffe example

7. Darwin Revolution Lyell: proposed a theory of uniformity
The notion of a gradual, lengthy molding of the earth’s geologic structure
Malthus: suggested that populations are limited in size by the resources available
If some resources were scarce there would be comptetition

8. Darwin Revolution
Alfred Wallace: studying geographic distribution of species in the Amazon
Sent his work to Darwin for advice

9. Darwin Revolution
Darwin’s view of life as expressed in The Origin of Species (1859) contrasted sharply with traditional beliefs
Natural Selection: a population can change over generations if individuals with certain heritable traits produce more viable offspring than other individuals
Evolutionary Adaptation: accumulation of inherited characteristics that enhance organisms’ ability to survive and reproduce in specific environments
Result of natural selection
Natural selection is a mechanism for evolution

10. Darwin Revolution
Taxonomy: branch of biology dedicated to the naming and classification of all forms of life
Binomial Nomenclature: two-part naming system that includes the organism’s genus and species
Carolus Linnaeus

11. Darwin Revolution
Fossils: found in sedimentary rock, are remains or traces of organisms from the past
Provide evidence for the theory of evolution
Paleontology: study of fossils

12. Darwin Revolution
Gradualism: geological theory that sates that profound changes in Earth’s features over the course of geological time are the result of slow, continuous processes
Uniformetarianism: geological processes that have shaped the planet have not changed over the course of Earth’s history

13. Natural Selection
Charles Darwin’s voyage on the HMS Beagle in 1831 was impetus for the development of his theory of evolution
Botanist John Henslow arranged for Darwin to sail around the world as ship’s naturalist
Descent with Modification: refers to Darwin’s idea that all living organisms are related by descent (they evolved) from a remote common ancestor

14.  Remote Common Ancestor

15. Natural Selection Theory of Natural Selection:
Natural Selection is the differential success in reproduction (the unequal ability of individuals to survive and reproduce) that results from the interaction between individuals that vary in heritable traits and their environment
Natural Selection can produce an increase over time in the adaptation of organisms to their environment
If an environment changes over time, or if individuals of a particular species move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species

16. Natural Selection Major Points: Observations about populations:
Populations have the reproductive capacity to increase in numbers over generations
As populations expand, resources will dwindle; individuals will run out of food, living spaces, and other resources
Individuals will end up competing for dwindling resources

17. Natural Selection Observations about genetics:
Individuals of a certain species share certain traits (gene pool)
Individuals of a natural population vary in details of their shared traits (different alleles for a gene)
Traits have a heritable basis, in genes. New variations arise from mutations.

18. Natural Selection Inferences:
Certain forms of a shared trait may make the bearer more competitive for scarce resources
Individuals better able to secure scarce resources tend to produce more offspring
Alleles associated with an adaptive trait become more frequent in a population

19. Natural Selection
How can we explain the giraffe through natural selection?

20. Natural Selection
Artificial Selection: process by which species are modified by humans
Plants and animals are specifically chosen to breed with the desired goal of producing offspring with specific characteristics

21. Natural Selection
Population: group of interbreeding individuals who live in a certain geographic area
Smallest unit that can evolve
Individuals cannot evolve
Natural selection can only work on heritable traits (traits passed from organism to offspring)

22. Darwin’s Theory Explains a Range of Observations
Explains changes in living populations
Ongoing evolution of drug-resistant bacteria
Homology: related species share characteristics resulting from common ancestry
Homologous Structures: variations on a structural theme and are anatomical signs of evolution
Ex. Forelimbs of mammals that are now used for a variety of purposes
Can you think of any examples?

23. Homologous Structures: variations on a structural theme and are anatomical signs of evolution
Ex. Forelimbs of mammals that are now used for a variety of purposes

24. Darwin’s Theory Explains a Range of Observations
Vestigial Organs: structures of marginal, if any, importance to the organism
Remnants of structures that served important functions in the organisms’ ancestors
Ex. Pelvis and
leg bones found
in some snakes

25. Darwin’s Theory Explains a Range of Observations
Molecular Homologies: shared characteristics on the molecular level
Use of the same genetic code written in DNA or other molecular similarities
Because genetic code is shared by all organisms, it s likely that all species descended from a common ancestor

26. Darwin’s Theory Explains a Range of Observations
Biogeography: refers to the geographic distribution of species
Species that live closer together tend to be more closely related than those that do not
Species that are endemic to a certain geographic location are found at that location and nowhere else

27. Darwin’s Theory Explains a Range of Observations
Darwin’s theory of evolution through natural selection explains the succession of forms in the fossil record
Transitional fossils have been found that link ancient organisms to modern species, just as Darwin’s theory predicts