AP Environmental Science: Chapter 5 1. Explain how southern sea otters act as a keystone species in kelp beds. The otters help to keep sea urchins and other kelp-eating species from depleting highly productive and rapidly growing kelp forests, which provide habitats for a number of species in offshore coastal waters. Without southern sea otters, sea urchins would probably destroy the kelp forests and much of the rich biodiversity associated with them. Explain why we should care about protecting this species from extinction. People love to look at these charismatic, cute, and cuddly animals as they play in the water. As a result, they help to generate millions of dollars a year in tourism income in coastal areas where they are found. Another …show more content…
Most populations live in clumps because the resources a species needs vary greatly in availability from place to place, so the species tends to cluster where the resources are available. Second, individuals moving in groups have a better chance of encountering patches or clumps of resources, such as water and vegetation, than they would searching for the resources of their own. Third, living in groups protects some animals from predators. Fourth, hunting in packs gives some predators a better chance of finding and catching prey. Fifth, some species form temporary groups for mating and caring for young. 6. Describe four variables that govern changes in population size and write an equation showing how they interact. Four variables – births, deaths, immigration, and emigration- govern changes in population size. A population increases by birth and immigration (arrival of individuals from outside the population) and decreases by death and emigration (departure of individuals from the population): Population change = (Births + Immigration) – (Deaths + Emigration) Age structure: Percentage of the population (or number of people of each sex) at each age level in a population. What are three major age group categories? 1) Organisms not mature enough to reproduce (the pre-reproductive age) 2) Organisms capable of reproduction (the reproductive stage) 3) Organisms too old to reproduce (the post-reproductive