1. The Whale and the Virus: How scientists study evolution
Chapter 1.1 and 1.3

2. Biological evolution
Darwin (1859):
Descent with modification

3. Biological evolution Darwin (1859): Descent with modification
Mid 20st Century to today
Any change in the inherited traits of a ________ that occurs from one _________ to the ____
Evolution is a process by which _________ of organisms change over time

4. Biological evolution Darwin (1859): Descent with modification
Mid 20st Century to today
Any change in the inherited traits of a population that occurs from one _________ to the ____
Evolution is a process by which _________ of organisms change over time

5. Biological evolution Darwin (1859): Descent with modification
Mid 20st Century to today
Any change in the inherited traits of a population that occurs from one generation to the next
Evolution is a process by which _________ of organisms change over time

6. Biological evolution Darwin (1859): Descent with modification
Mid 20st Century to today
Any change in the inherited traits of a population that occurs from one generation to the next
Evolution is a process by which populations of organisms change over time

7. Evolution explains the diversity of life
From the very large
e.g., a whale 3 x 101 m long
to the very small
e.g., a virus 10 x 10-8 m across

8. Understanding evolution has practical biomedical implications (Chapter 18)
How do pathogens become drug resistant?
What is the source of new pathogens?

9. Evolution case studies
1.1 Whales: mammals gone to sea

10. Terminology in section 1.1

11. 1 - Lineage
A chain of ancestors and their descendants. A lineage may be
the successive generations of organism in a single population,
the members of an entire species during an interval of geological time,
or a group of related species descending from a common ancestor.

12. 2 - Character
A recognizable attribute of any kind

13. 3 - Homology
Characters that are the result of shared common ancestry

14. 4 - Synapomorphy
A derived trait shared that evolved in the immediate common ancestor and is shared by all of its descendants (although the trait may be modified or even lost)

15. 5 – Convergent Evolution
similar features from different ancestors in different lineages as a result of ecological equivalence (chapter 10)

16. Examples Similar features are analogous not homologous
“Fish” and Whales

17. A whale is not a “fish” (a vertebrate with fins rather than limbs and that uses gills for respiration)

18. If a whale is not a “fish”, then what is it?
How do we know this?

19. How do we know whales are mammals?
Whales share synapomorphies with mammals __
Similarities with fish arose through ________ ________
Hair, Mammary glands, three bones in the middle ear, endothermy

20. But what group of mammals are whales related to?
Carnivorans (dogs cats, bears, seals, etc.)?
Manatees?
Some other group of mammals?

21. Genetic Evidence Comparing DNA Sequences Indicates Whales Are Artiodactyls
Phylogenetic tree made from interspersed DNA elements. Four transposon
insertions, at loci 4-7, define a clade of whales and hippos.

22. What does the fossil record show about whale evolution?

23. Documenting the transition from land to water
Fossil analysis of hindlimb loss
Changes in the skull and inner ear.
Isotopic analysis of fossil teeth

24. Fossil whales share synapomorphies with modern cetaceans as well as more primitive features (Fig. 1.4)
Dorudon, a 40 million year old whale
Fig. 1.4

25. The synapomorphic astragalus ankle bone

26. Fossils reveal links to land mammals
Shape of astragalus in the hind limb of the ancestors of modern whales indicates they are artiodactyls
Fig. 1.7

27. Fossil sequence documents transition from land to water (Fig. 1.8)
Traits in living whales emerged gradually, not all at once.
The fossils shown are only a fraction of the fossil whales discovered in recent decades.
(Fig. 1.8)

28. Isotopic analysis of fossil teeth (Fig. 1.9)
Terrestrial animals drink freshwater; marine animals drink saltwater
O18/O16 ratio higher in saltwater
Higher ratio in teeth of marine animals

29. Fossils document hindlimb loss (vestigial structure)

30. Fossils document hindlimb loss (vestigial structure) (Fig. 1.11)

31. Why would whales adapt to an aquatic lifestyle?
50 million years ago, the ancestors of modern day whales were small four legged terrestrial mammals
Thick bone density made it easier escape predators in the water
The inner ear adapted to allow the whales to move quickly under water and avoid vertigo
Skeletons of two early whales

32. Pakicetus a 50 million year old terrestrial whale (Fig. 1.5)
Petrosal fused with skull not tympanic as in later cetaceans (poor directional hearing in water)
Artiodactyl astragalus, thickened bones
Involcrum: In all cetaceans, the medial wall of the ectotympanic is very thick, as indicated by the red line, associated with underwater hearing

33. Pakicetus: freshwater - semiaquatic habitat

34. Ambulocetus (Fig 1.6): a fossil whale with hind limbs

35. Georgiacetus
the hip bones were not fused to the spine which suggests that the Georgia Whale probably could not support its own weight out of the water. Lived in seawater

36. Changes in gene expression led to hindlimb loss
Cetacean embryos initiate hind-limb bud development.
In the 5th week of gestation, the genes responsible for hind limb development are no longer expressed
The bud arrests and degenerates
Chapter 10 discusses regulation of limb development
(Fig. 1.10)

37. Research gives more clues about whale evolution
Loss of teeth in baleen whales
Evolution of brain size and complexity
Whale diversity over evolutionary time

38. Baleen whales lost teeth
Ancestors of all modern whales had teeth
Earliest baleen whales had teeth and small patches of baleen
Baleen completely replaced teeth in Mysticetes
Genes for building teeth disabled

39. Evidence
Lateral view of mysticete fetus (Balaenoptera physalus - fin whale) with dissection showing tooth buds in the upper jaw

40. Humans have greatly reduced whale populations.
Small populations put some cetaceans at risk of extinction (Figs and 1.15)
Humans have greatly reduced whale populations.
Small populations are more susceptible to disease, pollution, etc.
Reduced genetic diversity (Chapter 6)
Chinese river dolphin is extinct

41. Evolution case studies
Whales: mammals gone to sea
Viruses: the deadly escape artists
We will cover this at the end of the semester

42. 1.3 Evolution: A Tapestry of Concepts

43. Natural Selection
A mechanism that can lead to evolution, whereby differential survival or reproduction of individuals (DARWIN)
causes some genetic types to replace (outcompete) others.

44. Mutation and Recombination
Cause variation (early 20th Century)

45. Genetic Drift
Evolution arising from random changes in the genetic composition of a population from one generation to the next.

46. Phenotypes
Measurable aspects of organisms, such as morphology (structure), physiology, and behavior.
Genes interact with other genes and with the environment during development of the phenotype.

47. end