Chapter 5 bio population – Flashcards
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What are the four main characteristics of a population?
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geographic distribution density growth rate age structure
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What is a population's geographic distribution?
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It is the area inhabited by the population.
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Another term for geographic distribution is
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range
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What is population density?
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It is the number of individuals per unit area.
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What is the equation with which you can calculate population density?
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population density= # of individuals unit area
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What three factors can affect population size?
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a. The number of births b. The number of deaths c. The number of individuals that enter or leave the population
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If more individuals are born than die in any period of time, how will the population change?
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it will grow
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Immigration
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The movement of individuals into an area (the population grows)
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Emigration
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The movement of individuals out of an area (the population decreases)
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How will a population change if there is abundant space and food and if the population is protected from predators and disease?
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The population will multiply, and the population size will increase.
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When does exponential growth occur?
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It occurs when individuals in a population reproduce at a constant rate.
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What are three ways that a growth rate may be stated, or expressed?
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It may be stated as a doubling time, a birthrate per female, or a percentage of growth per year.
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Under ideal conditions with unlimited resources, how will a population grow?
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Such a population would grow exponentially.
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When resources become less available, how does population growth change?
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It slows or stops.
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When does logistic growth occur?
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It occurs when a population's growth slows or stops following a period of exponential growth.
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What is the carrying capacity of the environment for a particular species?
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It is the largest number of individuals that the given environment can support.
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What is a limiting factor?
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It is a factor that causes population growth to decrease.
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How do different limiting factors affect populations?
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Some limiting factors affect a population more strongly as the population grows larger. Others limit a population's growth regardless of the size of the population.
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What is a density-dependent limiting factor?
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It is a limiting factor that depends on population size.
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When do density-dependent factors become limiting?
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They become limiting only when the population density reaches a certain level.
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When do density-dependent factors operate most strongly?
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They operate most strongly when a population is large and dense.
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What are four density-dependent limiting factors?
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Disease Predation Parasitism Competition
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When populations become crowded, what do organisms compete with one another for?
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They compete for food, water, space, sunlight, and other essentials of life.
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The mechanism of population control in which a population is regulated by predation is called a(an)
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predator-preyrelationship
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What are the prey and what are the predators in the predator- prey relationship on Isle Royale?
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The prey are moose, and the predators are wolves.
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Why does the wolf population on Isle Royale decline following a decline in the moose population?
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The wolf population declines because there is less for the wolves to feed upon.
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How are parasites like predators?
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Like predators, parasites take nourishment at the expense of their hosts, often weakening them and causing disease or death.
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A limiting factor that affects all populations in similar ways, regardless of population size, is called a(an)
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density-independent limiting factor
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What are examples of density-independent limiting factors?
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Examples include unusual weather, natural disasters, seasonal cycles, and certain human activities, such as damming rivers and clear-cutting forests.
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What is the characteristic response in the population size of many species to a density-independent limiting factor?
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The population size characteristically crashes.
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How does the size of the human population change with time?
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It tends to increase with time.
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Why did the population grow slowly for most of human existence?
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Life was harsh, and limiting factors kept population sizes low.
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Why can't the human population keep growing exponentially forever?
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Earth and its resources are limited.
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What is demography?
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It is the scientific study of human populations.
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What factors help predict why the populations of some countries grow faster than others?
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Factors include birthrates, death rates, and the age structure of the populations.
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The hypothesis that explains why population growth has slowed dramatically in the United States, Japan, and much of Europe is called the
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demographic transition
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Throughout much of human history, what have been the levels of birthrates and death rates in human societies?
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Human societies have had high birthrates and equally high death rates.
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What factors lower the death rate?
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Advances in nutrition, sanitation, and medicine lower the death rate.
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What do age-structure diagrams graph?
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They graph the numbers of males and females in different age groups.
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What do the age structures of the United States and of Rwanda predict about the population growth of each country?
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The age structure in the United States predicts a slow but steady growth rate for the near future. The age structure in Rwanda predicts a population that will double in about 30 years.
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By 2050, the world's population may reach how many people?
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It may reach more than 9 billion people.
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What may cause the growth rate of the world population to level off, or even slow down?
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That may happen if countries that are currently growing rapidly move toward the demographic transition.
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What do many ecologists suggest will happen if the growth in human population does not slow down?
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There could be serious and lasting damage to the environment as well as to the global economy.
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What kind of limiting factor depends on population size?
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density dependent
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What occurs when the individuals in a population reproduce at a constant rate?
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exponential growth
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What is the movement of individuals into an area called?
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immigration
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What occurs when a population's growth slows or stops following a period of exponential growth?
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logistic growth
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What is a mechanism of population control in which a population is regulated by predation?
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predator prey relationship
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What is the tendency of a population to shift from high birth and death rates to low birth and death rates called?
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demographic transition
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What is the largest number of individuals a given environment can support called?
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carrying capacity
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What is the scientific study of human populations called?
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demography
