Evolution - Foundations

---

The subject of evolution is a very important one in the field of biology. Ever since Charles Darwin and Alfred Wallace proposed the theory in 1859 the way we look at the world, ourselves as well as the dynamic change of species within it, was altered. Evolution permeates every level of biology from ecosystems to the organism as well as the world of the cell. It is crucial that a beginning biology student gets a solid foundation of the facts of evolution since nothing truly makes sense in biology without them. This section of the course focuses on an introduction to evolution and natural selection with an emphasis on macroevolution. These principles will be a valuable tool as you continue to study the different aspects of zoology this semester.

"There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved".      Charles Darwin: On the Origin of Species, 1859

1. Define the concept of evolution?
2. In the past it was thought that life was static and unchanging. Briefly describe how this view of the world was challenged, leading towards our current understanding of life as dynamic and ever-changing.
3. Briefly mention some of the individuals involved in the process of altering our perception of how life evolved. How did each indiviual contribute to Darwin's thinking?
4. What changes occurred in the field of geology challenging the static world view?
5. What is the geological record? What determines the boundaries in the record? Can you name the different eras (with approximate beginnings and endings in time)? Can you name the geological periods within each era in the correct order? Can you pinpoint the approximate time of each period?
6. How did Lamarck contribute towards our understanding of evolution?
7. What was the importance of Charles Darwin?
8. Can one say that "On the Origin of Species" is a crucial book within the biological sciences? Why or why not?
9. Use the finches and tortoises of the Galapagos islands as examples of how Darwin started to understand how life changes over time due to the process of evolution.
10. What role did Alfred Russell Wallace play in terms of our understanding of evolution?
11. What are the six major areas of evidence that support evolution?
12. Give at least four reasons for why some species are more common in the fossil record? Is the record "biased"? Explain.
13. The evolution of the horse is a prime example of vertebrate evolution. What aspects of the horse changed over the last 60 million years? What kind of changes are thought to have triggered this macroevolutionary change in the ancestors of the modern horse?
14. What is a transitional fossil? Examples?
15. Does the fossil record support evolutionary theory? Why or why not?
16. Briefly explain the evolution of modern whales (watch the video clip below).
17. Define the concept of homologous structures. Give an example!
18. What are analogous structures? Vestigial structures? Examples of each?
19. Why do the early stage embryos of a fish, a chicken, a mouse and a human have gill slits?
20. What is the focus of the field of biogeography? How does the field support evolution?
21. How do you explain that fossils of certain reptiles are found in both West Africa as well as on the East coast of Brazil?
22. How has our understanding of plate tectonics affected our view of evolution?
23. How can the sequencing of genes from different organisms tell us something about evolutionary relationships?
24. What is microevolution?
25. Explain the concept of the molecular clock.
26. Why would two different species such as a dog and a human have more genes in common than a beetle and a human?
27. Explain the difference between evolution and natural selection.
28. Evolutionary change can either be gradual or punctuated. Explain.
29. Can we learn something about evolution from artificial selection (e.g. breeding dogs)?
30. What is the importance of genetic variation in the process of evolution?
31. Organisms often produce an enormous amount of offspring. Why do not all the offspring survive?
32. Explain the following: "Natural selection leads to differential reproductive success"?
33. Populations are the units of evolution. Why cannot individuals evolve?
34. Use the Hummingbird study (watch the video clip) as an example of natural selection. What are the characteristics of the individual birds that natural selection is acting upon?

Lecture Outline/Notes:

Introduction/Background: Evolution (definition) Marine Iguanas Older ideas:     Greece     Scala Naturae / Life is static and unchanging     Prevailed for about 2,000 years Changes - The Scientific Revolution     Use of the scientific method Challenges to the idea of a young Earth and static species     Field of Geology (Hutton/ Lyell)     The Fossil Record (Cuvier)     The concept of change (Lamarck)         [understand Lamarck's incorrect theory of "the inheritance of acquired characteristics" (example: giraffes)]

Charles Darwin     Background     Voyage of the Beagle - 1831-36     Discoveries on the voyage         South America     The Galapagos         The Marine Iguana         Tortoises         Darwin's Finches         Thomas Malthus     Role of Variation     Charles Darwin published "On the Origin of Species by the Means of Natural Selection" in 1859. The introduction to the book is quite interesting. Read the book online! : - )

Who Was Charles Darwin? [video 6 minutes]

Alfred Wallace's work and travels; co-discovered the theory of natural selection (selections of his work). As a young naturalist Wallace traveled extensively through the Neotropics as well as the Malayan Archipelago. These years are well described in the first part of David Quammen's book "The Song of the Dodo". Wallace independently developed the mechanism for evolution based on his extensive observations of the natural world.

Is Evolution Just a Theory? [video 6 minutes]

1. Taxonomy and Systematics:
    Classification of organisms with the help of taxonomy and systematics leads to the separation of species into "natural" groups. What does "natural" refer to in this context? What degree of evolutionary relatedness can be associated with these groups (taxa)?

2. The Fossil Record definition: remains of life from the past more than 300,000 species of fossil organisms have been described formation of fossils record of past life     some species dominate in the fossil record          the record is biased because:         (linked to..         hard parts present (bone/shell)         habitat (oceans, close to wetlands, rivers)         abundance (high population)         distribution (large area)         prevalence in time (all species go extinct - the longer a species exists the more likely they will be part of the record)         (In addition: consider surviving geological destruction and being found by a curious human) The evolution of horses is a prime example of evolutionary change     huge and solid record of fossils from these taxa     visible changes in size, toes, teeth     cause of change: climate changes? There are numerous transitional fossils in the fossil record Whales evolved from terrestrial animals.  The ancestors to modern whales had legs as shown by the fossil record.  Changes in the fossil record of animals over time Role of Extinctions

Whale Evolution [video 7 minutes]

3. Comparative Anatomy
Biologists compare different anatomical features of organisms. Similarities and differences in anatomy can provide evidence about evolutionary relatedness.
Example: homologous structures
    e.g. limbs of birds, humans, porpoise, reptile and a bat
    Functions are different but the structures have the same evolutionary origin.
Analogous Structures
Vestigial Structures (e.g. in the skeletons of the Greenland whale and the python snake one can still find the rudiments of limbs).

4. Comparative Embryology
Comparing the early development of organisms. Try it out! 
Study the images of the early development of several classes of the vertebrates. These embryos are very similar at early stages but quite different as development proceeds.
E.g. gill arches present in all of them at an early stage. Why? In a fish these structures are part of the gills while in a human they become part of the middle ear. Why do they form during the early stages?  Compare the development of four different embryos. 
These organisms seem to follow the same developmental sequence during the early stages but take their own unique path as time goes on. The developmental process has been modified by evolution. The similarities during the early stages point to common descent, i.e. the vertebrates have a common ancestor about 500 million years ago.

5. Biogeography
The study of the distribution and abundance of life forms. Understanding historical geography is crucial for being able to explain the current distribution of organisms as well as the presence of fossils of life from the past.
Plate tectonics
The continents move (continental drift)
Film showing the movement of the continents over the last 700 million years.
The global geography has shifted drastically over this time.
As a biologist it is important to consider the geography of the past to be able to understand the current distribution of species on the planet.
 
 

6. Molecular Biology [Note: Darwin had no knowledge about genes and DNA even though he was aware of the fact that traits were passed down through time from parents to offspring]. Evolutionary changes on the level of DNA (in the genes) are often referred to as microevolution.  The sequencing and comparison of DNA has become a powerful tool in terms of understanding the evolutionary relatedness between different species. Certain important genes are relatively stable and change very slowly over time. This phenomenon is referred to as the molecular clock. By comparing the changes that have occurred in the genes between different living species we gain knowledge about the time that has passed since these organisms had a common ancestor. The more similar the sequences the closer the connection in time. The great apes are genetically very similar to us humans. Graphs showing the similarities between major taxa of organisms.

Cracking the Genetic Code

The Mechanisms: Natural Selection Definition Natural selection is just one out of many mechanisms that drives evolution. It is the one that is most well known as it is associated with Charles Darwin. Discussion of artificial selection/breeding as a comparison     e.g. the mustard plant family and other crops (corn, wheat, rice)     e.g. the breeding of dogs, horses, pidgeons and domestic animals in general   The Evolution of Dogs Natural Selection     Acts on the genetic variation within a population     Overproduction of offspring is the norm     Struggle for existence The three factors above lead to differential reproductive success. Examples of natural selection:      Peter and Rosemary Grant's wonderful studies of the Ground Finches on the Galapagos Islands. There are obvious changes in the bird populations (in e.g. the avergae beak size) in response to the available food sources (variety of seeds in different sizes) which in turn depends of the degree of precipitation over the years. Read Jonathan Weiner's book [ "The Beak of the Finch"].      Another commonplace example I would like you to understand is the evolution of resistance towards antibiotics that is becomong such a problem in medicine. The overuse and overprescription of antibiotics has led to a selective force that is allowing the adaptive trait of resistance to permeate populations of different bacterial species across the world (e.g. Mycobacterium tuberculosis - the causative agent of tuberculosis).      Watch the example of the hummingbird study. What characteristics are important for the survival of the individual hummingbirds? How does the environment affect these characteristics in the population over time? Why would the population change? It is important to remember that the population evolves over time (and not the individual).

Natural Selection - Hummingbirds [video 7 minutes]

Evolution: Stephen Jay Gould

Film: Nova - "What Darwin Never Knew"

• Geological Time
• Evolution of the Horse


Maps of the Past:

• Late Permian 255 million years ago
• Early Jurassic 195 million years ago
• End of Cretaceous 66 million years ago - Dinosaur Extinction
Maps of the Future:
• The World in 50 million years

• Understanding Evolution - Excellent site well worth exploring.
• Evolutionary Timeline - Excellent! Make sure to explore this link and refer to it as you go through the course. Excellent photos of fossils.
• Timeline -
• The Tree of Life
• Issues in Evolution
• Understanding Evolution: An article from Scientific American centered around several themes that often are misunderstood. Worth reading!
• Evolutionary Links: A collection of links to web sites focused on evolution.
• PBS - Evolution: PBS web site devoted towards the outstanding series "Evolution". This is possibly one of the best documentaries on evolution that has been made. Your local library is likely to have copies of the series and they are well worth watching. The web site has numerous sections exploring different aspects of evolution. A fun and informative site to explore.
• The Talk.Origins Archive: An excellent site that contains numerous contributions of articles and essays related to evolutionary theory including discussions and controversies. Recommended!
• Biology Book - Evolution I : An excellent overview of evolution with lots of graphics. The page may take a while to load unless you have a fast connection, but it is definitely worth the wait.
• Biology Book - Evolution II : Further information focused on the mechanisms of evolution.

Recommended Readings: Carl Zimmer: "Evolution - The Triumph of an Idea" Carl Zimmer: "The Tangled Bank" Carl Zimmer: "At the Water's Edge" Richard Dawkins: "The Blind Watchmaker" Richard Dawkins: "Climbing Mount Improbable" Douglas Futuyma: 'Evolutionary Biology" Jerry Coyne: "Why Evolution is True" Janet Browne: "Charles Darwin - Voyaging" Janet Browne: "Charles Darwin - The Power of Place" Richard Dawkins: "The Greatest Show on Earth" Richard Dawkins: "The Ancestor's Tale" Charles Darwin: "On the Origin of Species" Stephen Jay Gould: "Ever Since Darwin" Jonathan Weiner: "The Beak of the Finch" David Quammen: "The Song of the Dodo" Neil Shubin: "Your Inner Fish" Donald  Prothero: "What Fossils Say and Why it Matters"

Page created by: Peter Svensson Updated: February 11,  2015