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The reading for this unit is here:
Evolution 101 (UC Museum of Paleontology)
Read chapters of Evolution 101 called #1) An introduction to evolution; #3) Mechanisms: the processes of evolution and #4) Microevolution.
Terms:
| gametes - sexual reproduction cells: sperm and eggs |
| altruism - self-sacrificing behavior towards other individuals; behavior that benefits another organism at some cost to the individual |
| proxy - a stand-in for a different variable that is difficult to measure directly. For example, right plumage on a bird can be an indirect measure of health. |
| speciation - the production of new species |
1. What's the difference between evolution and natural selection?
Find definitions for evolution and natural selection:
evolution:
natural selection:
2. What are the necessary conditions for natural selection to occur?
A. There must be variation within the population.
- What causes variation within populations?
In lecture we will add a couple more mechanisms for variation.
- Give an example of variation within populations (the book cites the example of color; think of a different characteristic that can vary in natural populations).
B. The variation must be heritable - organisms must be able to pass on the variation to their offspring.
- What is an example of a heritable characteristic? a characteristic that is not heritable?
- Suppose a cow had a two-headed calf. Do you think a two-headed animal could produce a two-headed offspring? (use your best speculation here)
C. The variation must be change the liklihood of either survival or successful reproduction.
- Give some examples of variation that probably does not confer any advantage or disadvantage to the organism.
3. Evolutionary change without natural selection
- Use the Web site to find at least one possible mechanism for evolution (change in gene frequencies across generations) without natural selection.
5. Some apparently puzzling evolutionary patterns
Use the readings on sexual selection and kin selection to explain why natural selection might lead to these phenomena:
Male deer grow very large antlers that they drop and regrow each year. The antlers are very "expensive" for the deer to grow - a deer that is healing from a major injury or that has been ill will grow stunted antlers (the Biology Dept. has a great display of funky antlers in SQU 105). The antlers are not typically used for self-defense (deer use their hoofs on prospective predators) but are only used for ritual combat with other males. Why would deer evolve the growth of such an expensive frill?
Within a wolf pack, typically only a single pair - the alpha male and female - mate. The entire pack raises the resulting pups, hunting for them and defending them against predators. Why would a wolf invest its energy and put itself at risk for another wolf's pup?
We will do a variety of other puzzling situations in class.
2. Essay
We are often told that the human appendix is a vestigal organ with no apparent function. Explain the persistence of the appendix in at least three different ways, including explanations that invoke adaptation, and those which do NOT require natural selection.
One of the greatest puzzles in evolutionary biology is how complex or specialized structures evolve, especially structures which are not functional in a simpler form. For example, some dung beetles are camouflaged by looking like the excrement they eat. It's hard to imagine how this trait could evolve gradually. As Stephen Jay Gould has pointed out, there's not much adaptive advantage in looking 10% like a turd. Describe 3 different mechanisms by which this trait could have evolved.