Biology Chapter 35.1 35.2 Concept Checks

PRENTICE HALL BIOLOGY – “EXPLORING LIFE” CHAPTER 35 “Population and Community Ecology” Campbell, Williamson, Heyden Concept Checks for 35.1 and 35.2 35.1 – “A population is a local group of organisms of one species” Q1) Give an example of boundaries that ecologists use to study populations. A1. One example is the quadrat, which is a defined rectangle that marks the boundaries of observation, usually for studying population density. Q2) Contrast population size with population density. A1. Population size is the number of organisms, as opposed to the density, which is the number of organisms in a certain radius or area. Q3) Give an example of a population of organisms located near your school. Describe a method you could use to measure the density of this population. A1. The squirrels can be measured by marking them, and counting the amount recaptured in a certain area (mark-recapture method). Q4) What is the relationship between the terms species and population? A1. A population is a group of members from the same species. 35.2 – “There are limits to population growth” Q1) Describe how a population grows with unlimited food, space and water. A1. With unlimited food and water, the population will always be healthy and have long age. With unlimited space, there will be room to sustain the exponentially large population to come with this unlimited food and water supply. Q2) Describe what happens when a population reaches its carrying capacity in a particular environment. A1. Once the carrying capacity is being reached, the exponential growth will slow down stabilizing into a steady population. Q3) Compare density-dependent and density-independent factors, and give an example of each. A1. The main difference between the two is their effect on the population through density. For example, a density-dependent factor such as food availability affects the population based on its density, whereas a density-independent factor such as a hurricane, destroys everything regardless. Q4) What is a “boom-and-bust” population growth cycle? What might cause such a cycle? A1. A boom and bust cycle is a population that rapidly grows in number, then rapidly declines. The main cause of this cycle is a predator-prey relationship, in which the prey is hunted and the predator grows really fast, but then the predators die fast again because there’s no food, making the prey rapidly grow in number again and this loops forever.