June 22, 2011

Notes for the Evolution 101 course

A few notes from the Evolution 101 course from UC Berkeley [1]. I am guilty of rampant plagiarism however, I had to do so because the words used in the Evolution 101 course are precise and unambiguous.
  1. Evolution means that we're all distant cousins: humans and oak trees, hummingbirds and whales.
  2. Scientists constantly reevaluate hypotheses and compare them to new evidence. As scientists gather even more data, they may revise these particular hypotheses, rearranging some of the branches on the tree. For example, evidence discovered in the last 50 years suggests that birds are dinosaurs, which required adjustment to several "vertebrate twigs."
  3. We can reconstruct evolutionary relationships and represent them on a "family tree," called a phylogeny.
  4. Because a phylogenetic tree is a hypothesis about evolutionary relationships, we want to use characters that are reliable indicators of common ancestry to build that tree. For example, birds and bats both have wings, while mice and crocodiles do not. Does that mean that birds and bats are more closely related to one another than to mice and crocodiles? No. When we examine bird wings and bat wings closely, we see that there are some major differences.
  5. If you wanted to squeeze the 3.5 billion years of the history of life on Earth into a single minute, you would have to wait about 50 seconds for multi-cellular life to evolve, another four seconds for vertebrates to invade the land, and another four seconds for flowers to evolve — and only in the last 0.002 seconds would "modern" humans arise. Life began 3.8 billion years ago, and insects diversified 290 million years ago, but the human and chimpanzee lineages diverged only five million years ago.
  6. Evolution is the process by which modern organisms have descended from ancient ancestors. Evolution only occurs when there is a change in gene frequency within a population over time
  7. Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human. Humans are not "higher" or "more evolved" than other living lineages. Since our lineages split, humans and chimpanzees have each evolved traits unique to their own lineages.
  8. Mutation, Migration, Genetic drift, and Natural selection are the four processes that are the basic mechanism of evolutionary change
  9. Biologists use the word fitness to describe how good a particular genotype is at leaving offspring in the next generation relative to how good other genotypes are at it. So if brown beetles consistently leave more offspring than green beetles because of their color, you'd say that the brown beetles had a higher fitness.
  10. Natural selection is the simple result of variation, differential reproduction, and heredity — it is mindless and mechanistic. It has no goals; it's not striving to produce "progress" or a balanced ecosystem.
  11. A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest gene pool possible under natural conditions.
  12. All available evidence supports the central conclusions of evolutionary theory, that life on Earth has evolved and that species share common ancestors. Biologists are not arguing about these conclusions. But they are trying to figure out how evolution happens, and that's not an easy job. It involves collecting data, proposing hypotheses, creating models, and evaluating other scientists' work.
Now for a list of misconceptions [2]:
  1. Evolution is just a theory.
  2. Evolution is like a climb up a ladder of progress; organisms are always getting better.
  3. Evolution means that life changed by chance.
  4. Natural selection gives organisms what they need.
  5. Gaps in the fossil record disprove evolution.
  6. Teachers should teach both sides (read evolution and creationism) and let students decide for themselves.
The reason for this blog posts are as follows
  1. I am hearing "Evolution is just a theory" a lot these days.
  2. To end some debates I used to say "Teachers should teach both sides". I should stop saying this [2].
  3. I say used to say Humans evolved from Chimpanzees. This is also wrong [1].
  4. I used to wonder if random mutation and natural selection has a long term goal that ensures resources are sustained. Apparently there is no long term goal, as the course says that natural selection is mindless and mechanistic. This is important as evolution neither guarantees nor does it work towards sustaining the available resources.
[1] http://evolution.berkeley.edu/evolibrary/article/evo_01
[2] http://evolution.berkeley.edu/evolibrary/misconceptions_faq.php