How do animals maintain stable populations? Why is ensuring stability important for evolution?<\/p>\n\n\n\n
Populations with uncontrolled growth or insignificant growth are not stable populations. Certain behavioral strategies help promote stability through reproduction and choosing when to compete with others.<\/p>\n\n\n\n
Read more about stable populations and the behavioral strategies that can help protect stability.<\/p>\n\n\n\n\n\n\n\n
How animals decide when to reproduce is a complicated question. <\/strong>Some scientists, most notably zoologist Vero Copner Wynne-Edwards<\/a>, believe that animals control their reproduction rates to avoid overpopulating an area. They’re aiming for stable populations. However, this would be a group-selection based theory, which doesn\u2019t seem to mesh with the idea of the selfish gene. It\u2019s worth noting that Wynne-Edwards was a prominent champion of the group-selection theory of evolution, and his ideas are influential enough to be worth considering\u2014even if only to refute them.<\/p>\n\n\n\n Whatever the reason, it\u2019s clear that animal populations don\u2019t grow at the incredible rates they\u2019d be theoretically capable of. Many populations remain fairly stable, with birth and death rates roughly matching each other. Others, like lemmings, grow rapidly and then decline sharply, sometimes to the point of total extinction in a particular area.<\/p>\n\n\n\n Starvation is one major factor in keeping animal populations under control. If animals reproduce too quickly for an area to support, naturally many of them will starve. However, starvation cannot fully explain how animal populations stay under control. <\/strong>If starvation were the only control set on population size, scientists would expect all creatures to work like lemmings do: Their numbers would increase exponentially until the region couldn\u2019t support them, then suddenly crash as most of them starved. <\/p>\n\n\n\n Therefore, it\u2019s clear that there are methods limiting birth rates as well as death rates\u2014animals don\u2019t have infinite numbers of offspring. The question is not <\/strong>whether <\/em><\/strong>birth rates are controlled, but <\/strong>why <\/em><\/strong>they are controlled.<\/strong><\/p>\n\n\n\n The group-selection theory would say the reason is altruistic: Animals regulate their birth rates for the good of the entire population. The selfish gene theory<\/a> would say that it\u2019s selfish: Animals regulate their birth rates because it gives them and their offspring the best chance of survival<\/a>.<\/p>\n\n\n\n Game theory can be used to explain behaviors, especially at the population level. By using game theory, scientists can determine effective behavioral strategies. They can also find\u2014or at least approximate\u2014an ESS for a population made up of such behaviors. These behavioral strategies support stable populations.<\/p>\n\n\n\n The Prisoner\u2019s Dilemma is a logistical riddle closely tied to game theory. <\/strong>In the Prisoner\u2019s Dilemma there are two players, each with two options: Cooperate and Betray. Neither player knows which option the other has chosen, and they are not allowed to influence the other\u2019s choice in any way.<\/p>\n\n\n\n If both players choose Cooperate, they each get a significant payout\u2014but a smaller one than in the next situation. If one player Cooperates and the other Betrays, the betrayer gets a large payout while the cooperative player suffers a large penalty. If both players Betray, they each suffer a small penalty. Cooperation and betrayal are altruistic and selfish actions, respectively. Therefore, everything we know about the Dilemma could be compared to nature.<\/p>\n\n\n\n In any single instance of the game, the logical choice is to simply pick Betray. <\/strong>If your opponent chose Cooperate, you\u2019ll get a larger payout than if you\u2019d also chosen Cooperate. If your opponent chose Betray, you\u2019ll suffer a smaller penalty than if you\u2019d chosen Cooperate.<\/p>\n\n\n\n However, the strategy becomes much more complex if you play over and over again.<\/strong> Now one Always-Betray strategy can get stuck in a penalizing loop with another one, while more cooperative strategies have the chance to reap mutual benefits. Of course, an Always-Cooperate strategy will still lose every time to an Always-Betray strategy. <\/p>\n\n\n\nGame Theory and Behavioral Strategies<\/strong><\/h3>\n\n\n\n
Which Strategies Are the Most Effective?<\/strong><\/h3>\n\n\n\n