1. The Macroevolutionary Puzzle
Chapter 18

2. Fossils and the Great Deluge
Fossils of seashells have been found in rock layers high in the mountains
How did they get there?
Initial explanation was that they had been deposited during the biblical flood

3. Evidence of Past Life
1700s
Excavations unearthed similar fossil sequences in distant places
Scholars began to view these findings as evidence of the connection between Earth history and the history of life

4. What Do Fossils Tell Us?
As a result of mutations, natural selection, and drift, each species is a mosaic of ancestral and novel traits
All species that ever evolved are related to one another by way of descent

5. Macroevolution
The large-scale patterns, trends, and rates of change among families and other more inclusive groups of species

6. Fossils Recognizable evidence of ancient life
Fossilized hard parts (most common)
Trace fossils (indirect evidence)

7. Fossilization Organism becomes buried in ash or sediments
Rapid burial and a lack of oxygen aid in preservation
The organic remains become infused with metal and mineral ions

8. Stratification Fossils are found in sedimentary rock
This type of rock is formed in layers
In general, layers closest to the top were formed most recently

9. Radiometric Dating parent isotope in newly formed rock
after one half-lives
after two half-lives

10. Geologic Time Scale Archean eon (oldest interval)
Proterozoic eon
Paleozoic era
Mesozoic era
Cenozoic era (most recent)
Boundaries based on abrupt transitions in fossil record
Correspond to mass extinctions

11. Record Is Incomplete Fossils have been found for about 250,000 species
Most species weren’t preserved
Record is biased toward the most accessible regions

12. Continental Drift
Idea that the continents were once joined and have since “drifted” apart
Initially based on the shapes
Wegener refined the hypothesis and named the theoretical supercontinent Pangea

13. Changing Land Masses
420 mya
260 mya
65 mya
10 mya

14. Evidence of Movement
Wegener cited evidence from glacial deposits and fossils
Later was discovered that magnetic orientations in ancient rocks do not align with the magnetic poles
Discovery of seafloor spreading provided a possible mechanism

15. Plate Tectonics Earth’s crust is fractured into plates
Movement of plates is driven by upwelling of molten rock at mid-oceanic ridges
As seafloor spreads, older rock is forced down into trenches

16. Forces of Change
crustal margin of one plate being thrust under margin of another plate
mid-oceanic range
plumes of molten material

17. Comparative Morphology
Comparing body forms and structures of major lineages
Guiding principle:
When it comes to introducing change in morphology, evolution tends to follow the path of least resistance

18. Morphological Divergence
Change from the body form of a common ancestor
Produces homologous structures that may serve different functions

19. Morphological Divergence1 2 3
Morphological Divergence
PTEROSAUR 4 1 2
CHICKEN 3
STEM
REPTILE 2 3
PENGUIN 1 2 3 4 1 5 2
PORPOISE 4 3 5 1 2
BAT 3 4 5 1 2 3 4
HUMAN 5

20. Morphological Convergence
Individuals of different lineages evolve in similar ways under similar environmental pressures
Produces analogous structures that serve similar functions

21. Comparative Development
Each animal or plant proceeds through a series of changes in form
Similarities in these stages may be clues to evolutionary relationships
Mutations that disrupt a key stage of development are selected against

22. Altering Developmental Programs
Some mutations shift a step in a way that natural selection favors
Small changes at key steps may bring about major differences
Insertion of transposons or gene mutations

23. Development of Larkspurs
Two closely related species have different petal morphology
They attract different pollinators
side view
front view
D. decorum flower
side view
front view
D. nudicaule flower

24. Development of Larkspurs
Petal difference arises from a change in the rate of petal development 6
D. decorum 4
Petal length (millimeters) 2
D. nudicaule 10 20 40
Days (after onset of meiosis)

25. Similar Vertebrate Embryos
Alterations that disrupted early development have been selected against
FISH
REPTILE
BIRD
MAMMAL

26. Similar Vertebrate Embryos
Aortic arches
Adult shark
Early human embryo
Two-chambered heart
Certain veins

27. Developmental Changes
Changes in the onset, rate, or time of completion of development steps can cause allometric changes
Adult forms that retain juvenile features

28. Proportional Changes in Skull
Chimpanzee
Human

29. Comparative Biochemistry
Kinds and numbers of biochemical traits that species share is a clue to how closely they are related
Can compare DNA, RNA, or proteins
More similarity means species are more closely related

30. Comparing Proteins
Compare amino acid sequence of proteins produced by the same gene
Human cytochrome c (a protein)
Identical amino acids in chimpanzee protein
Chicken protein differs by 18 amino acids
Yeast protein differs by 56

31. Sequence Conservation
Cytochrome c functions in electron transport
Deficits in this vital protein would be lethal
Long sequences are identical in wheat, yeast, and a primate

32. Sequence Conservation
Yeast
Wheat
Primate

33. Nucleic Acid Comparison
Use single-stranded DNA or RNA
Hybrid molecules are created, then heated
The more heat required to break hybrid, the more closely related the species

34. Molecular Clock
Assumption : “Ticks” (neutral mutations) occur at a constant rate
Count the number of differences to estimate time of divergence

35. Taxonomy
Field of biology concerned with identifying, naming, and classifying species
Somewhat subjective
Information about species can be interpreted differently

36. Binomial System Devised by Carl von Linne
Each species has a two-part Latin name
First part is generic
Second part is specific name

37. Higher Taxa
Kingdom
Phylum
Class
Order
Family
Inclusive groupings meant to reflect relationships among species

38. Phylogeny
The scientific study of evolutionary relationships among species
Practical applications
Allows predictions about the needs or weaknesses of one species on the basis of its known relationship to another

39. A Cladogram
shark
mammal
crocodile
bird
feathers
fur
lungs
heart

40. Five-Kingdom Scheme Proposed in 1969 by Robert Whittaker Monera
Protista
Fungi
Plantae
Animalia

41. Three-Domain Classification
Favored by microbiologists
EUBACTERIA
ARCHAEBACTERIA
EUKARYOTES

42. Six-Kingdom Scheme EUBACTERIA ARCHAEBACTERIA PROTISTA FUNGI PLANTAE
ANIMALIA

43. Transitional Forms
Dromaeosaurus
Archaeopteryx