Question

the structure of a community is shaped by interactions among the populations making up the community. the most important kinds of interactions are competition, mutualism, predation, herbivory, and parasitism. state which of these five interactions is described in each of the examples that follow. then put a + or - in each of the parentheses ( ) to indicate whether the relationship is positive or negative for each organism. 1. sheep liver flukes ( ) feed on bile and can weaken or kill their hosts ( ). they are passed on to other sheep in the animals droppings. 2. grazing by introduced mountain goats ( ) has reduced the numbers of alpine wildflowers ( ) in olympic national park. 3. pest control specialists have brought in a moth ( ) to eat tansy ragwort, ( ) a poisonous weed. 4. mistletoe ( ) obtains nutrients from an oak tree ( ). 5. mycorrhizal fungi ( ) associated with roots obtain carbohydrates from a tree, while enabling the tree ( ) to absorb water and minerals more efficiently. 6. in parts of north america where their populations overlap, asian pheasants ( ) and quail ( ) utilize the same food and nest sites. 7. a bee ( ) pollinates a tropical orchid ( ) by being tricked into \mating\ with the flower; the bee uses a perfume from the flower to attract a mate. 8. the influenza virus ( ) attacks the lining of the respiratory tract and is passed from person ( ) to person by contact or airborne droplets. 9. red - winged blackbirds ( ) arrive earlier on the breeding grounds, but are forced to the edges of a marsh by larger, later - arriving yellow - headed blackbirds ( ). 10. lions ( ) hunt large herbivorous mammals such as zebras and wildebeest ( ). 11. a tropical acacia tree ( ) sprouts in the midst of other species of trees ( ) and grows up toward the light. 12. some species of acacia ( ) are infested by ants ( ) that live in enlarged tree thorns and feed on special nutrient - rich leaves. as the acacia grows, the ants prune away leaves and branches of competing trees.

Explanation:

1. Parasitism: Flukes benefit (+), hosts are harmed (-).
2. Herbivory: Goats benefit (+), wild - flowers are harmed (-).
3. Predation: Moth benefits (+), tansy ragwort is harmed (-).
4. Parasitism: Mistletoe benefits (+), oak tree is harmed (-).
5. Mutualism: Fungi benefit (+), tree benefits (+).
6. Competition: Both species are negatively affected (-) due to resource limitation.
7. Mutualism: Bee benefits (+), orchid benefits (+).
8. Parasitism: Virus benefits (+), person is harmed (-).
9. Competition: Red - winged blackbirds are negatively affected (-), yellow - headed blackbirds benefit (+) in terms of better territory.
10. Predation: Lions benefit (+), herbivores are harmed (-).
11. Competition: Acacia tree benefits (+) in terms of light access, other trees are negatively affected (-) due to shading.
12. Mutualism: Ants benefit (+), acacia benefits (+).

Answer:

1. Parasitism; Flukes (+), Hosts (-)
2. Herbivory; Mountain goats (+), Alpine wildflowers (-)
3. Predation; Moth (+), Tansy ragwort (-)
4. Parasitism; Mistletoe (+), Oak tree (-)
5. Mutualism; Mycorrhizal fungi (+), Tree (+)
6. Competition; Asian pheasants (-), Quail (-)
7. Mutualism; Bee (+), Tropical orchid (+)
8. Parasitism; Influenza virus (+), Person (-)
9. Competition; Red - winged blackbirds (-), Yellow - headed blackbirds (+)
10. Predation; Lions (+), Herbivorous mammals (-)
11. Competition; Tropical acacia tree (+), Other species of trees (-)
12. Mutualism; Ants (+), Acacia (+)