Dynamic Nature of Ecosystems

The peppered moth (Biston betularia) has two forms, a white-bodied and a dark-bodied form. The table provided shows the percentage of each type in a moth population over several years. The data provided on the shift in population of the peppered moth could support a claim that this population is responding to a change in the environment. In order for this data to support that claim, what other data would be needed?

• Data showing that eventually there were no more dark-bodied moths after 1985.

• Data showing that, in 1965, the two forms migrated from different habitats.

• Data showing a steady change in the color of trees in this habitat between 1965 and 1985

• Data showing that in the years after 1985 the trend reversed leading to more dark moths.

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An illustration of a water lily is provided. If annual rainfall increased and caused ponds in this ecosystem to become deeper, how might the traits of these water lilies change after many generations?

Answer explanation

The populations of lilies would change to have longer stems.

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What is a disruption to an ecosystem that can lead to shifts in its populations?

Answer explanation

A natural hazard such as a forest fire or a flood could lead to shifts in an ecosystem’s populations.

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If a sudden outbreak of disease severely reduced the number of coyotes in an ecosystem very rapidly, what might the resulting changes to the local food web look like?

Answer explanation

Natural prey of the coyote will increase, while any predators of the coyote would search for a new food source or move away.

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Information on brown tree snakes is provided along with information on the island of Guam. Brown tree snakes were first brought to Guam in 1950. Which of the following would provide evidence that the change to this environment brought about by the introduction of the brown tree snake has had an effect on the populations of organisms that lived on Guam?

• The population of lizards on Guam in 1960 was very small.

• The longest brown tree snake ever found on Guam measured three meters in length.

• Any of the military bases on Guam were closed in the 1980’s.

• Several other species of snakes were known to live on Guam before 1950.

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The trout is a fish that lays its eggs in cold fresh water but spends some of its life in the ocean. Trout eat smaller fish. The graph provided shows the population of trout in the state of Wisconsin between the years 1999 and 2014. Which change to the ecosystem had the largest effect on the population of trout in Wisconsin?

• 1. The rise in population of smaller fish in Wisconsin lakes between 2010 and 2011

• 1. A shift in ocean currents that occurred in 2000 and again in 2001

• 1. A hard freeze of many of the lakes in Wisconsin in the winter of 2006

• The slow rise in lake temperatures in Wisconsin between 1999 and 2014

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Match the following:

• Ecosystem

• Changes in ecosystem factors over time

• Population

• A group of individuals of the same species

• Resilience

• the ability to recover from a disturbance

• Ecosystem dynamics

• All the biotic and abiotic factors of an environment

• Dynamic

• Current change or progress

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The introduction of invasive species to an ecosystem can change the dynamic of the ​ ​ (a)   among the species. Disruptions to any ​​ (b)   components of an ecosystem can lead to shifts in all of its ​ (c)   . Volcanoes and earthquakes are ​ (d)   disturbances that affect ecosystems. Removing a habitat by cutting down trees or draining a lake is a ​ (e)   disturbance that affects an ecosystem.

• interactions

• populations

• natural

• physical or biological

• human-made

• invasive

• resilience

• disturbances

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Bank swallows are birds that make their nests on the edges of rivers. Bank swallows can’t swim or breathe underwater. They feed on ying insects and, in the spring, lay four or ve eggs. Which of the following observations would provide evidence that the population of bank swallows was affected by a change in the environment?

• Swallows that lay four eggs one year may lay ve eggs the following year.

• Swallows share a food source with other animals that also eat insects.

• The largest swallows catch and eat more insects than the smallest ones.

• Fewer swallows build nests along the river when the water level rises.

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Interrelated changes among the biotic and abiotic

factors in an ecosystem over time

• Ecosystem Dynamics

• Succession

• Deforestation

• Commensalism

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