216 ❯ STEP 4. Review the Knowledge You Need to Score High
sacrificing their lives by stinging intruders that pose a threat to the queen bee. (Sounds
to us like they need a better agent.) Another example involves vampire bats that vomit
food for group mates that did not manage to find food.- Coefficient of relatedness.This statistic represents the average proportion of genes that
two individuals have in common. Siblings have a coefficient of relatedness (COR) of
0.5 because they share 50 percent of their genes. This coefficient is an interesting sta-
tistic because it can be expected that an animal that has a high COR with another
animal will be more likely to act in an altruistic manner toward that animal. - Dominance hierarchies.A dominance hierarchy among a group of individuals is a rank-
ing of power among the members. The member with the most power is the “alpha”
member. The second-in-command, the “beta” member, dominates everyone in the
group except for the alpha. It pretty much rocks to be at the top of the dominance hier-
archy because you have first dibs (choice) on everything (food, mates, etc.). The domi-
nance hierarchy is not necessarily permanent—there can always be some shuffling
around. For example, in chimpanzees, an alpha male can lose his alpha status and become
subordinate to another chimp if power relationships change. One positive thing about
these hierarchies is that since there is an order, known by all involved, it reduces the
energy wasted and the risk from physical fighting for resources. Animals that know that
they would be attacked if they took food before a higher-ranking individual wait until it
is their turn to eat so as to avoid conflict. Keep in mind that dominance hierarchies are
a characteristic of group-living animals. - Foraging.A word that describes the feeding behavior of an individual. This behavior is
not as random as it may seem as animals tend to have something called a search image
that directs them toward their potential meal. When searching for food, few fish look
for a particular food; rather, they are looking for objects of a particular size that seem to
match the size of what they usually eat. This is a search image. In an aquarium at meal-
time, if you watch the fish closely, you will see them zoom around taking food into their
mouths as they swim. Unfortunately, sometimes the “food” they ingest is the bathroom
output of another fish that happens to be the same size as the food and is floating nearby.
Simply because the fish dropping is the appropriate size and fits the search image, the
fish may take it into its mouth for a second before emphatically spitting it out. - Inclusive fitness.This term represents the overall ability of individuals to pass their genes
on to the next generation. This includes their ability to pass their owngenes through
reproduction as well as the ability of their relatives to do the same. Reproduction by rel-
atives is included because related individuals share many of the same genes. Therefore,
helping relatives to increase the success of passage of their genes to the next generation
increases the inclusive fitness of the helper. The concept of inclusive fitness can explain
many cases of altruism in nature. - Optimal foraging.Natural selection favors animals that choose foraging strategies that
take into account costs and benefits. For example, food that is rich in nutrients but far
away may cost too much energy to be worth the extra trip. There are many potential
costs to traveling a long distance for some food—the animal itself could be eaten on the
waytothe food, and the animal could expend more energy than it would gain fromthe
food. You knowthat you have displayed optimal foraging behavior before. “Hey, do
you want to go to Wendy’s?” “Uhh... not really, it’s a really long drive... let’s go to
Bill’s Burgers down the road instead.” - Reciprocal altruism.Why should individuals behave altruistically? One reason may be
the hope that in the future, the companion will return the favor. A baboon may defend