What term is used to describe a species whose population is rapidly decreasing and may disappear completely? a) endangered b) extinct c) indigenous d) threatened 37) zebra mussels are native to poland and the soviet union. they were probably transported to the united states via trans-oceanic vessels. with no natural predators in the united states, zebra mussels a) will eventually die out due to lack of food supplies. b) caused a huge decline in native clam and mussel populations. c) compete unsuccessfully with native mussels and quickly die. d) successfully share the niche with native mussels and clams. 38) a non-native organism that is released into a new ecosystem, such as kudzu in the southeastern united states is called a a) pioneer species. b) threatened species. c) endangered species. d) non-indigenous species. 39) what is the role of the beaver in its ecosystem? a) it is a foundation species and the main source of food for the natural predators of its ecosystem. b) it is a keystone species that modifies its natural environment by damming streams to form wetlands. c) it is a dominant species, as it has the greatest number of individuals among all the mammalian species of its ecosystem. d) it is an endangered species as it has the least number of individuals among all the mammalian species of its ecosystem. 40) the greatest biodiversity on earth is found in the biome. a) taiga b) grasslands c) deciduous forest d) tropical rainforest