Avariety of pear tree, known as bradford, was
originally introduced into the eastern united
states in the 1960s. today, this tree is crowding
out other plants in these states. this situation
best illustrates
(1) an unintentional negative effect of altering
an ecosystem
(2) how a foreign species is controlled in the
eastern united states
(3) that the introduction of a foreign species
does not affect food webs
(4) that serious environmental consequences
can be avoided by importing a foreign
species