Ch 4 - ReviewQuestions:PossibleAnswers 1. What are the two...

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Review Questions: Possible Answers 1. What are the two fundamental kinds of population growth curves? What are the causes and consequences of each? The two types of population growth curves are the J-curve and the S-curve. “The J-curve demonstrates population growth under optimal conditions, with no restraints. The S-curve shows a population at equilibrium. The J-curve is caused by exponential growth of a population and the absence of mechanisms to cause the population to level off; the consequence of this type of growth is a population crash and a reduction in the carrying capacity. The S-curve is caused by exponential growth of a population until natural mechanisms cause the population to level off and continue in a dynamic equilibrium. The causes of this type of growth are the various biotic and abiotic factors that limit a population’s increase (environmental resistance).” 2. Define biotic potential and environmental resistance and give factors of each. Which generally remains constant, and which controls a population’s size? Biotic potential is “the number of offspring (live births, eggs laid, or seeds or spores set in plants) that a species may produce under ideal conditions.” A species’ biotic potential remains constant. Environmental resistance is “(t)he combination of all the abiotic and biotic factors that may limit a population’s increase. Environmental resistance may increase or decrease depending upon population size.” Environmental resistance controls a population’s size. The biotic potential of a species causes the population size to increase. While the population size is relatively small, the environmental resistance is low and the rate of population growth increases. As population size increases, the environmental resistance increases and the rate of population growth declines. The population size of some species remains relatively level with moderate increases and decreases in population size. Other species have more dramatic fluctuations in population size. 3. Differentiate between the terms critical number and carrying capacity. What is density dependence? Critical number is the minimum size of a population below which it will not reproduce. The survival of the species is unlikely below the critical number. The carrying capacity is a characteristic of an ecosystem and “is the maximum population that a given habitat can support without the habitat being degraded over the long term.” Therefore, the critical number is the smallest number of individuals within a species that is required for the species survival while the carrying capacity is the largest number of individuals within a species that an ecosystem can support. Carrying capacity is a characteristic of an ecosystem, while critical number is a characteristic of the species. Density dependent factors are those environmental resistance factors that, as the population size increases there is an increase in “mortality, (such) that population growth ceases or declines.” When population
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Ch 4 - ReviewQuestions:PossibleAnswers 1. What are the two...

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