|AP Biology, Chapter 22
Descent with Modification: A Darwinian View of Life
Endless Forms Most Beautiful
1. State the two major points that Charles Darwin made in The Origin of Species concerning
Current organisms evolved from ancestral species
Natural selection is a mechanism for evolution
22.1 The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species
Scala Naturae and Classification of Species
2. Correlate Aristotle's scala naturae and the Abrahamic view of the fixity of species.
Organisms occupy rungs on a scale of complexity
Already perfectly adapted, so unchanging
Species created by a higher being
Designed perfect already
3. Describe Carolus Linnaeus's contribution to Darwin's theory of evolution.
Grouped organisms hierarchically by shared physical traits
Unintentionally created a system for identifying evolutionary kinship
Ideas About Change over Time
4. Describe Georges Cuvier's contribution to paleontology.
Scientifically documented the fossils in the Parisian rockpile
Concluded: the deeper, the older, the more different the fossils
Recognized the extinction of species
5. Explain how Cuvier and his followers used the concept of catastrophism to oppose the
theory of evolution.
Averred catastrophes defined strata
Said different organisms in overlying strata hadn't evolved but migrated
6. Explain how the principle of gradualism and Charles Lyell's theory of uniformitarianism
influenced Darwin's ideas about evolution.
Current gradual processes can explain land forms
Deep time: Earth millions and millions of years old
Uniformitariamism: mechanisms are constant over time
= the opposite of catastrophism
Darwin proposed evolution by slow, gradual change
Lamarck’s Hypothesis of Evolution
7. Describe Jean Baptiste Lamarck's model for how adaptations evolve. Explain the
challenges to Lamarck's ideas with respect to current understandings of biology.
Recognized descent with modification in the fossil record
Innate drive to become more complex
Species change, become better adapted, by use and disuse
Acquired characteristics passed to offspring
22.2 Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life
The Voyage of the Beagle
8. Describe how Darwin used his observations from the voyage of the HMS Beagle to formulate and support his theory of evolution.
South American species resembled one another
Observations suggested an old, constantly changing Earth
Related species on the Galapagos were adapted to local environments
Darwin’s Focus on Adaptation
9. How did Darwin’s view of adaptation inform his hypothesis?
Adaptation: trait enhancing survival and reproduction
Adaptations therefore passed on as a result
10. Describe how Lyell and Alfred Russel Wallace influenced Darwin.
Lyell: urged Darwin to publish
Wallace: sent manuscript in 1858; matched Darwin's unpublished work
The Origin of Species
Descent with Modification
11. Explain what Darwin meant by "descent with modification."
All life originated from a single, unknown prototype
Descendents spread and became adapted to new habitats
Branching from common ancestors
Saw Linneaus’ hierarchical taxonomy as evolutionary history
Artificial Selection, Natural Selection, and Adaptation
12. Distinguish between artificial selection and natural selection.
Artificial is human-directed selective breeding
Natural is differential survival based in variability of useful traits
13. Describe the three inferences Darwin made from his observations that led him to propose natural selection as a mechanism for evolutionary change.
Variation in heritable traits differential survival
Exponential growth + limited resources struggle for existence
Small changes over generations adaptation of populations
14. Explain how an essay by the Rev. Thomas Malthus influenced Charles Darwin.
Malthus, 1798, An Essay on the Principle of Population
Populations grow exponentially, resources don't
Darwin incorporated that as differential survival
15. Explain why the population is the smallest unit that can evolve.
Individuals are tested during their lifetime
Populations record the results when they are gone
Natural Selection: A Summary
22.3 Evolution is supported by an overwhelming amount of scientific evidence
Direct Observations of Evolutionary Change
Natural Selection in Response to Introduced Plant Species
The Evolution of Drug-Resistant Bacteria
16. Using some contemporary examples, explain how natural selection results in
Galapagos finch beak shape changes in response to food change
Antibiotic resistant bacteria predominate with overuse
Transplanted guppy size increases in response to predator
17. Explain how homologous structures support Darwin's theory of natural selection.
Homology: similarity inherited from a common ancestor
Anatomical and Molecular Homologies
Ex: homologous structures of vertebrate forelimbs
Ex. embryonic structures
Ex.: vestigial structures; remnants of structures useful in other species
Ex.: similar DNA and protein sequences
Homologies and “Tree Thinking”
18. How are homologous groupings expressed in evolutionary trees?
Branch points = common ancestors with a trait
All branches from that point had the trait
Usually correlated with multiple types of data
A Different Cause of Resemblance: Convergent Evolution
19. Contrast homologous and analogous structures and account for convergent evolution.
Structures inherited from a common ancestor
Ex>; amniote embryonic membranes
Structures developed independently
Ex.: wings of birds, butterflies
Evolution of the same adaptation in response to the same pressure
Ex.: gliding in flying squirrels and sugar gliders
The Fossil Record
20. How does the fossil record document the patterns of evolution?
Lineages of major groups show acquisition and alteration of homology
Sufficient transitional forms are present
21. Explain how biogeography supports the evolutionary deductions based on homologies.
Group origins and spreading patterns parallel the evolution of continents
Islands contain related endemic species
What is Theoretical About Darwin’s View of Life?
22. Explain the problem with the statement that Darwinism is "just a theory." Distinguish
between the scientific and colloquial use of the word "theory."
Evolution is based on a vast amount of historical evidence
Commonly "theory" is used as scientists use "hypothesis"
Darwin's proposed mechanism is theoretical