Text: Evolution by Mark Ridley; Read carefully, thoroughly

Sections: must attend and lead discussion; present write-up of material

Problem sets: required and very helpful by exam time

Study groups: 2-4 people review test and lectures: questions for office hours

Exams: in Salomon

Lecture topics: sequence of material

Goals: Develop a way of thinking about the diversity of life on earth. Ask the questions: how do we account for biological diversity? how did it "develop" (i.e., evolve)? how do we analyze it? why are we here? Tall orders: No one formal approach or answer to these issues

A perspective: understand the space and time of the universe we live in

We tend to have an egocentric view of our existence

SPACE: The planet earth, solar system, galaxy are one very, very minor part of it

TIME: The cosmic calendar, December 31 (from Sagan's Dragons of Eden)

Some questions:

is there life out there? What does it look like?

Similar events? Does it use DNA?

If it uses DNA is this evidence for Creation or Evolution?

This is why we insist that you form study groups: you need to discuss these ideas


Evolutionary biology is the study of the patterns of organic diversity and the processes that generate those patterns.

Fundamental Observations: Diversity: Notice diversity of form when you walk to class; Notice diversity of humans in this room; birds&butterflies have a common ancestor, but look very different

Evolutionary biology is also the study of the "good" fit of organisms to their environments: the study of adaptation. This involves both the recognition of a pattern (good fit) and testing hypotheses of mechanism to account for the pattern. Good fit: flounder (camouflage and bottom dwelling habit); stick insect (camouflage); marine organisms with fusiform bodies

Evolution as Explanation

Hierarchy of organization in biology.

Evolutionary tree ("Cladogram ") of whale, seal, penguin, shark, sea snake: knowing the relationships of these organisms gives us one level of "appreciating the diversity" of the natural world. Seals and penguins are distantly related but have comparable body forms for life in water. (see also figure 1.6, pg. 12).

Proximate and ultimate causation (the how and why). Observing these patterns we want to know why things are the way they are and how things came to be that way. Thorns on cacti: why=to reduce predation(herbivory); how=those with spines: experience less predation: more offspring? Warbler migration: why=more food, daylight, habitat; how=those that left their wintering sites left more offspring?

Evolution provides an explanation for many issues of general human concern and welfare: the population genetics used in DNA fingerprinting; natural selection that has resulted in extremely dangerous of antibiotic resistant microbes; a new view of medical issues known as Darwinian medicine that addresses issues of why we get sick, whether to treat a fever and why our knees and lower backs are frequent sources of mechanical failure; and concern for the long-term genetic consequences of living and reproducing in our own waste products of pollution and global warming.

Obtaining scientifically sound explanations for these observations is very difficult and is the task of evolutionary biology as a discipline. Easy to fall into "adaptationist" story telling. "Just-So Stories"


Change over time (fact)

Archaeopteryx: clear change over time from a common ancestor

how would we think about evolution if we had no fossils?

Bacteria in your intestine: they reproduce, evolve etc.

gene frequency changes in populations - mathematics of natural selection

Both are evolution; different time scales

Descent with modification (a fact)

Apes to humans: it is a fact that we are descended from apes

Your parents to you: clear similarities, but obvious differences

evolution is really just genetics let run over many, many, generations

Splitting[=speciation] (a fact)

Groups of organisms represented by many varied forms (=species?) Tanagers have similar form but are clearly different species

Evolution by natural selection (a theory)

Darwin and Wallace's theory provided a mechanism by which this descent with modification might operate. Evolution as a process and Natural Selection as a mechanism are separable: evolution can occur without natural selection (more later)

What is so appealing about the study of evolution is that it provides a coherent context in which to think about all of biology: Everything in biology has gotten here by evolution: glycolysis, the krebs cycle, nervous systems, even rap music (by cultural evolution)

We must then draw on material from many disciplines, from astronomy and geology through biochemistry and genetics to ecology and behavior, to really account for the staggering diversity of life on earth.

But it is not just the "other" life on earth that is evolving. Humans are notable in that by the nature of their very actions are altering their evolutionary fate. Many organisms do this, but humans have the intellectual abilities to do this by design. And that is both fascinating and frightening at the same time.