Regents Living Environment Test Preparation Practice

    Alteration And Recovery Of Ecosystem


    Base your answer to question 5 on the information below and on your knowledge of biology.

    Dissolved oxygen (DO) can be found in an aquatic ecosystem and is often one factor that affects the size of populations of aquatic organisms. Water temperature is very important in determining the amount of DO in a water supply. The colder the temperature of the water, the more DO the water can hold.


    Base your answers to questions 6 on the information below and on your knowledge of biology.

    Decline in the Amphibians

    Declines in amphibian species, such as frogs, toads and salamanders, might affect the ways in which ecosystems function. Amphibians prey on many types of small organisms that survive by consuming leaf litter (leaf material on the ground of ecosystems). These small organisms include animals such as earthworms, centipedes, millipedes, pill bugs, and many species of insects. In turn, amphibians are preyed on by fish, herons, chipmunks, turkeys, foxes, coyotes, and other animals.

    Human activities often cause a reduction in the size of amphibian populations. As amphibian populations are reduced, the organisms that are preyed on by amphibians increase in number. As the populations of small forest organisms increase, the amount of leaf litter decreases. The decrease in the amount of leaf litter on the forest floor may have negative effects on the forest ecosystem.


    Base your answers to question 7-8 on the diagram below and on your knowledge of biology. The diagram indicates a change in an ecosystem.

    ecology, succession, change of ecosystems over time, ecology, stability of ecosystems, alteration and recovery of ecosystem fig: lenv62018-examw_g23.png


    Base your answers to questions 9 on the information below and on your knowledge of biology. The diagram represents an ecological process that occurs in New York State over a long period of time.

    ecology, succession, change of ecosystems over time fig: lenv62019-examw_g26.png


    Base your answers to questions 10 on the information below and on your knowledge of biology.

    Coral Reef Ecosystems

    There are many ecological interactions that maintain the biodiversity present in coral reefs. In addition to coral, microscopic algae, seaweed, sea grasses, sponges and worms, and a variety of fish are among the organisms that live in reef ecosystems. Ocean currents often link different reef systems and move organisms from one reef area to another. This movement is a factor in repopulating a reef that has been damaged by environmental changes.

    One environmental change involves an increased growth of seaweed. When the population of seaweed increases, the reef shifts from a coral-dominated ecosystem to a seaweed-dominated ecosystem. This change disrupts the relationships between the organisms that live there.

    Studies have shown that, as the density of seaweed in a reef area increases, the number of fish that eat the seaweed in that area decreases. This may be due to the presence of more predators, or the taste of the more mature plants. The fish move to areas where there is less seaweed growth. As this trend continues, the reef areas are taken over by the seaweed. Once this happens, it is very hard to remove the seaweed and restore the reef to a healthy ecosystem.

    In addition to this problem, temperature changes are threatening the ocean currents that connect the reef systems. A change in the currents would reduce the movement of fish larvae from one area to another. This contributes to the seaweed problem.