Discussion Questions April 12th

Discussion questions
Apr 12
What Darwin never knew (online NOVA documentary at http://www.pbs.org/wgbh/nova/beta/evolution/darwin-never-knew.html)
Please note that you can also read the transcript for this documentary; a link to the transcript is available at the same URL.

1. What are some of the recent discoveries that give us insight into how the diversity of life evolved?
Darwin’s observations helped us to understand that diversity in species is a result of change. Just like humans, animals vary in looks even if they are of the same species (I.e. finches). These changes may occur from environmental conditions: Natural Selection. The Galapagos islands, for instance, varied in seed sizes which made finches develop different beak sizes depending on what island they populated.

2. Present some of the developmental evidence for Darwin’s Tree of Life.
According to Darwin’s Tree of Life, all species are connected. Humans, for example, are descendants of fish in which during the development of the human embryo it appears to have gills in one of the phases before birth. These gill-like parts, however, turn into the inner ear of a human while remaining gills to a fish.

3. Part of Darwin’s Theory of natural selection is the idea that different individuals within the same species compete against each other. Explain how this competition led to evolutionary change in:

(1) The Galapagos finches: As mentioned earlier, the Galapagos islands varied in environmental conditions. Seed sizes were different on each island, and in order for a finch to survive, its’ beak size had to adapt to the force that was required to consume the seed depending on the island a finch populated.

(2) Pocket mice in the Pinacarte Desert: Two mice of the same family have evolved different appearances as a means of survival. Eruptions from ancient volcanoes changed parts of desert which means for the mice to survive it will have to change as well. The lighter mouse is camouflaged to lighter brown areas of the desert, which helps it to hide from predators such as owls and coyotes. Where the dark lava remains, mice have developed darker coats to avoid being captured by predators.

4. Give a couple of examples of single mutations that we can identify in particular genes that have proven to be very beneficial.
The Colobus monkey had a mutation in gene that enabled it to see in color: it can distinguish healthy red leaves from old green leaves.
A mutation in an Antarctic fish produces a sort of antifreeze in its blood to survive in freezing waters.

5. Why is it so surprising that humans only have about 23,000 genes?
Humans typically place themselves on high level in the animal kingdom, but the genes show that humans don’t require many genes to be made., according to Olivia Judson. Some of our main genes are similar to other animals.

6. What does the “switch” that Sean Carroll found in fruit flies do?
It allows some fruit flies to have spots and others to not have any spots appear. The gene oversees the details of where the spots will appear on the fruit fly or not.

7. Why do Kinglsey and Schluter think they’ll find the same switch sticklebacks as in manatees, even though the rear fins were lost at completely different times in these lineages?
There findings suggest a pattern of unevenness. Traces of discovered bones resemble the bone structure of manatees today which may explain the evolution of this observation.

8. The fact that Hox genes control the development of fins in paddlefish suggests that the evolutionary transition of fins to limbs wasn’t all that dramatic. Explain.
These Hox genes demand simple changes/ mutations for such differences to occur. Much like the “switch,” the transition of fins to limbs is relatively short.

9. Hansell Stedman found a mutation in the human genome that should lead to muscle problems. But it turns out this mutation has benefited us? Why and how?
This muscle ends ups working to create the muscles that allow us to chew and close the jaw. Unlike apes, however, humans chew with a fraction of the force of ape. Our skulls can expand allowing our brains to grow.

10. Where are most of the genetic differences between humans and chimps located? (i.e., what kind of DNA?)
The differences between the humans and chimps are not in the genes, but they are in the “switches.”: pieces of DNA that turn genes on or off.