SG_Unit_I_Day_4

SG_Unit_I_Day_4 - Keesha Fausto Study Guide: Unit I...

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Keesha Fausto Study Guide: Unit I (Ecology) Day 4 - Territoriality + Niche Partitioning Read: Colinvaux, Why Big, Fierce Animals Are Rare , Chapters 15 and 16. 1. Explain Colinvaux's argument as to why density-independent mortality during the winter seems an inadequate explanation for constancy in number of birds that breed in the spring. Density independence in death mortality seems an inadequate explanation for constancy in the number of birds that breed in the spring. Whatever happens in the winter, the same number of birds is let through every year to the spring, despite the fact that each winter starts off with a different number of birds and the fact that not every winter is alike. 2. Briefly describe the events that lead to territory formation and nesting in the yellowhammer. Describe the roles played by males and females and the significance of "fighting" and singing. The yellowhammer as well as other birds of different species would fly in flocks during the fall and winter, and as spring approached, the males are seen to spend time on a perch experimenting with song. This goes on as the birds, confined to their perches, chase away anything that goes near it. The flocks eventually break up and the males are left alone. Their songs become a mating call to the female birds of their species, and are challenges to their male counterparts. This left each perched male evenly spaced. When they sung their songs, they attracted females. They kept on singing even after they attracted their mate, which is believed to be a sort of sign as a lasting bond between the pair. The female would get familiar of her new surroundings. The male and female yellowhammer pair would build their nest, rear their young, and forage for food near that males “assigned” perch, as both refused intruders. The pair is kept together by this mutual feeling of home. This assured them of their without losing any of it to competing individuals of their own kind. 3. If a male who fails to gain a territory never gets to reproduce, shouldn't natural selection favor the tendency to fight ferociously, even to the death, for a territory? Explain why or why not. Natural selection probably will not favor the tendency to fight ferociously, even to the death, for the spot at territory and the chance to breed if a male fails to gain a territory because the male will use all his resource and all his energy in fighting for territory. If he finally gets it, his chances of reproducing are low because of all the energy he used in fighting. 4. Explain how territoriality explains the constancy in the number of birds that breed each spring. After the effects of crowding during the winter have brought the number of breeding birds to order, the physical size of breeding territories cannot be compressed beyond a certain point. This hypothesis implies that there must be years in which there is a considerable population
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SG_Unit_I_Day_4 - Keesha Fausto Study Guide: Unit I...

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