mountain lion population decreased. The organisms in the food web live near large cattle ranches. Over many years, mountain lions would kill a few cattle on occasion. One year, a few ranchers hunted and killed many mountain lions to prevent future loss of their cattle. Later, ranchers noticed that animals from this food web were eating large amounts of grain from their farm fields. Identify two specific populations that most likely increased in number after the mountain lion population decreased.

Less mountain lions = more deer and rabbits Explain how killing many mountain lions caused other ranchers in the community to have less grain and grass. Less mountain lions = more deer and rabbits more deer and rabbits = less grain and grass

Base your answers to questions 56 through 59 on the information below and on your knowledge of biology. There has been an increase in the number of dead birds found on the beaches of the Great Lakes. These birds were poisoned by a bacterial toxin in the lake water. The birds do not ingest enough water to become sick directly from the toxin found in the lake water. Scientists think that the cause of the increasing bird deaths lies with an invasive species— the zebra mussel. This freshwater organism was introduced into the Great Lakes accidentally by humans, and has become well established in the Great Lakes. Zebra mussels filter out microscopic organisms, as well as the toxins found in the lake water. The toxins become concentrated in the zebra mussels, which are eaten by small fish called gobies, and the gobies are eaten by the birds. The concentration increases in each level of the food chain. It appears that the introduction of the zebra muscles into the Great Lakes has resulted in a new food chain that increases the concentration of the naturally occurring toxins and passes dangerous levels on to these top-level predators. This process is known as bioaccumulation.

Biomagnification (Bioaccumulation) Each “step” up the food chain requires eating more of the level below. This means each step has less organisms and energy. It ALSO means each step will concentrate poison from the level below. Click me!