1. Miniature Versions. Sometimes what evolves on an island is a species much smaller than its mainland relatives, such as pygmy elephants, small deer, horses, et cetera. What sort of island conditions would give an advantage to smaller individuals that wouldn't work on the mainland?
2. Giant Versions. It also happens that what evolves on the islands may be much larger versions of the mainland relatives, as seen in giant tortoises, lizards, and the like. What island conditions might lead to such a development?
4. Self-feeding baby birds. Many birds, like chickens, grouse, or ducks, hatch from the egg able to feed themselves, not helplessly dependent on parents like you often think baby birds would be. Among these birds, the adults share a trait that is connected to this ability. What is it?
5. Stand-out colors. Some animals, instead of being camouflaged to blend into their environ- ment, are marked in colors and patterns that make them stand out instead. Blacks are often used with whites and/or yellows, and reds are also common. It's not hard for predators to see these animals. What possible traits would favor this appearance?
6. Sexual selection traits. Some animal features are not for survival, but to attract the attention of mates, kind of an advertisement that says, "you should make babies with me, because they'll be more likely to make their own babies." Such features as moose antlers, peacock tails, and human breasts, even jewelry and a fancy car are of this type. But hidden in these sexual selection traits are messages about pure survival. What about such features makes it reasonable to think that the possessor actually is better able to get the essential resources of life?
7. Severity of disease. It is generally thought that a really severe, life-threatening disease will be associated with a disease-causing organism that has only recently (in evolutionary time) "moved in" to this species of host - after long association, over several generations, it's expected that the disease organism will be less likely to make the host really sick. This obviously is an advantage to the host, but how is it an advantage to the disease organism?
Disease Symptoms. Some symptoms of diseases are reflections of our own bodies' attempts to fight off the disease organism, but many have no such function. What other purpose might a symptom like coughing, or sweating, or diarrhea have if NOT part of our defenses?
Genetic diseases. With discoveries starting with sickle-cell anemia, it has been found that wide-spread genetic diseases (cystic fibrosis is another example, schizophrenia possibly another) can, under certain circumstances, give an advantage to those that carry them. Explain why, from an evolutionary point of view, this pretty much had to be true.
First Written 1996; Last Update 2009; Web Version 2001, M. McDarby
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