Topic 2 Day 4

In the past, coyotes lived throughout the western prairies and central Rocky Mountains in North America. Over time, the coyotes’ range has expanded. Humans have tried trapping and hunting coyotes to decrease their numbers. However, biologists currently estimate the number  of coyotes to be at an all-time high. Which of the following statements best explains why the number of coyotes continues to increase despite increases in death rates due to hunting and trapping?

• 1.  Coyote lifespan is increasing, so only the oldest coyotes encounter hunters or trappers.

• 1.  Coyote birth rates remain high, so more coyotes are added to the population than are removed.

• 1.  Coyotes are migrating more often,  so male coyotes have more fights over territories. 

• 1. Coyotes have to compete with more species, so the coyote emigration rate has increased.

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The graph below shows the relationship of a lynx population to a snowshoe hare  population.

Which of the following statements best explains why the lynx population usually increases after the snowshoe hare population increases?

• 1. Lynx move over large areas to hunt snowshoe hares.

• 1. The lynx birth rate increases when more snowshoe hares are present.

• 1. High snowshoe hare populations cause a decrease in the lynx birth rate.

• 2. The populations of both animals decrease during the winter and increase during the summer.

A population of flat-tailed horned lizards was found in a geographically isolated area. In 2002, the size of the population was about 25,500. In 2004, the size of the population was about 32,800. Which of the following statements explains the change in the size of the lizard population from 2002 to 2004?

• 1. The birth rate was greater than the death rate.

• 1. The emigration rate was greater than the birth rate.

• 1. The death rate was greater than the immigration rate.

• 1. The emigration rate was greater than the immigration rate.

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Pheasants are a type of bird. Two male pheasants and six female pheasants were introduced onto an island with abundant food and few predators. Within six breeding seasons, the pheasant population increased from eight birds to two thousand birds. Over time, however, the growth rate of the population slowed. Which of the following statements describes the most likely reason for this decrease in population growth rate?

• Females built smaller nests, which decreased the birth rate.

• Competition for resources increased, which increased the death rate.

• Large numbers of birds needed mates, which increased the immigration rate.

• Fewer eggs hatched each successive year, which decreased the emigration rate.

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Most populations introduced to a new ecosystem grow until factors such as lack of food and overcrowding limit their growth, as illustrated in the population growth graph. What does the portion of the graph labeled B represent?

• 1. Exponential growth

• 1. Decrease in birthrate

• 1. Increase in death rate

• 1. Slowing growth

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A small population colonized an isolated island. Over time, the size of the population increased to its carrying capacity, as represented in the graph below.

Which of the following conditions will most likely keep the population at its carrying capacity?

• 1. A death rate of zero

• 1. A death rate that is half the birth rate

• 1. A death rate equal to the birth rate

• 1. A death rate that is twice the birth rate

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A population of rabbits in an area of Northern Florida was monitored to learn more about the biotic and abiotic factors that affect the population size. The graph below shows data collected about the rabbit population size for 30 generations.

Based on the data above, what can be correctly stated about the rabbit population?

• 1. More rabbits have immigrated than have emigrated.

• 1. The number of deaths is greater than the number of births.

• 1. The rabbits appear to have reached carrying capacity.

• 1. A lethal virus killed a majority of the rabbits at the twentieth generation.

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A growth curve for a population of crabs on a coral reef is shown below. Which statement best explains what is happening at Point A?

• Population growth decreases as individual crabs get older.

• The population is stabilizing as it approaches carrying capacity.

• Destruction of habitat is causing a decline in the population of the crabs.

• The introduction of a new predator is causing a decline in population growth of the crabs.

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