Terms to know: species selection, group selection, individual selection, kin selection , altruism, inclusive fitness, Hamilton's inequality, b, r, c, haplodiploidy

Questions:

1. It is observed that females of a species of deer are physiologically capable of having two offspring at a time, but that most females actually have only one offspring at a time.
1. How could the difference between actual number of offspring and physiologically possible number of offspring be explained through group selection?
2. How could the difference between the actual and physiologically possible number of offspring be explained through natural selection at the individual level?
3. Which explanation (group selection or individual selection) is more likely, and why?
2. Given that the theory of group selection doesn't generally work, what is the main contribution of Wynne-Edwards' book on group selection to the field of evolutionary biology as a whole?
3. Some aspects of pathogens (organisms that cause diseases) have been hypothesized to evolve through group selection.  In what condition does this occur?  Why is group selection possible for this situation when it will not occur in most situations.
4. The first sentence of section 16.1 in your textbook states that "altruism is a central paradox of Darwinism." Later in the paragraph it is noted that Darwin found the existence of altruism to be a "special difficulty, which at first appeared to me insuperable, and actually fatal to my whole theory."  Why is altruism so hard to explain based on natural selection?  Altruism would seem to be beneficial to species containing altruists -- why does this NOT explain why altruism would evolve?
5. What is altruism?  How was altruism proposed to evolve by group selection?  How was altruism proposed to evolve by kin selection?  Which of these forms of evolution (group selection or kin selection) is considered unlikely to occur, and therefore an unlikely explanation for the evolution of altruism?  Why is this form of evolution considered unlikely?
6. Some sea anemones (animals in the phylum Cnidaria, related to corals and jellyfish) reproduce asexually and live in colonies of genetically identical individuals.  It is observed that very little aggression occurs within a colony, but individuals from different colonies are aggressive (they sting each other with the stinging cells on their tentacles.)  Give a plausible evolutionary explanation for the difference in aggression within and between colonies.
7. Explain why Hamilton's Formula, br-c>0, gives the conditions under which altruism evolves.  In your answer, fully explain what b, r, and c represent and why each is important to understanding the evolution of altruism.
8. Why might haplodiploidy make the evolution of altruism more likely than it would be in a diploid species?
9. Many plants have what are called inducible defenses -- they produce toxic compounds in their leaves when their leaves are damaged as insects start eating their leaves.  This is thought to be an adaptation to save energy -- they only produce the compounds when they are needed to prevent herbivory. It has been suggested by the results of some studies that plants may also give off chemicals that affect neighboring plants, so that when insects have damaged one plant, other neighboring plants are signaled, and also start producing toxic compounds.  The neighbors are thus better protected against insect damage.  Assume that it is costly for the original plant to produce the chemicals that warn the neighbors.  Would you expect to see chemicals that warn neighbors evolve more frequently in species that reproduce clonally, and grow in stands of genetically identical species, or in species that reproduce sexually and have their relatives disperse far away from them?  Why?
10. Explain how each of the following differences between two haplodiploid wasp species would affect the likelihood of evolution of altruism by explaining how each difference would affect one or more of the terms in Hamilton's inequality (consider each difference separately from the others):
1. In one species, each female lays her eggs one at a time in very different locations, while in the other species each females lays all her eggs together in a nest.
2. In one species, developing larvae are fed on a scarce resource so that a single individual can only find enough food to raise a small number of offspring, while in the other species developing larvae are fed on an abundant resource, easy to obtain in large quantities by a single individual.
3. In one species, each female mates with only one male, and then has many offspring.  In the other species each female mates with a large number of males, and then has many offspring.
4. In one species, nests are subject to high levels of fungus infection so that a single individual can only keep a few eggs fungus free (fungus infected eggs die.)  In the other species, there is little fungal infection and single individuals can successfully raise many different eggs.
11. Define "inclusive fitness".  Why may inclusive fitness be a better indicator of whether a trait may evolve than relative fitness, based on the number of surviving offspring of individuals, is.
12. A famous evolutionary biologist (J.B.S. Haldane) supposedly once said "I would lay down my life for two brothers or eight cousins."  Explain the principle to which he was referring to when he said this, and explain where the numbers "two" and "eight" in this statement come from.