Ohio Graduation Test for Science – March 2006
Annotated Item 3
Standard and Benchmark Assessed:
Standard: Life Sciences
Benchmark: F. Explain the structure and function of ecosystems and relate how ecosystems change over time.
Multiple Choice Question:
Use the following information to answer questions 2 – 4.
Ants and Seed Dispersal
Many species of plants in the family Proteaceae produce seeds with fleshy structures called “elaiosomes.” Elaiosomes are protein-rich “food patches” that are attractive to ants.
In the Cape region of South Africa, native ants carry the Proteaceae
eeds back to their nests where they eat the elaiosomes and discard the
seeds in underground chambers. A species of Proteaceae seeds,
Mimetes cucullatus (M. cucullatus), will successfully germinate after
being placed underground by the native ants.
An ant native to Argentina was accidentally introduced to the Cape’s
shrub lands and displaced many of the native ants. The non-native
ant also feeds on elaiosomes. However, they discard the seeds on the
surface. This allows the seeds to be eaten by rodents or destroyed by
brush fires. The effects on the dispersal of the Proteaceae M. cucullatus in a typical situation are shown in the diagram below.
3. The relationship between the Proteaceae plants and the native ants is described as
This multiple choice question asks students to identify what type of relationship exists between the Proteaceae plants and the native ants. Students are provided both textual information and a diagram describing the relationships between two species of ant and one species of plant. Students must reflect on the interactions between the native ant species and the plant species in the ecosystem as they are described in the provided text. Students are told that the ants eat part of the plant seed, the elaiosome, and bury the remains of the seed which then germinate. Students should recognize that since the ants use part of the plant for food, the ant is benefited by the plant. Since the plant seed is carried to a new location and buried by the ant, the plant is also benefited as its life cycle continues. Answer choice D is correct because this is a mutualistic relationship where both species benefit from their interaction in this ecosystem. Answer choice A is incorrect because the native ant species does not have a parasitic relationship with the plant. In a parasitic relationship one organism (parasite) lives in or on another organism (host) and derives subsistence from it causing harm to the host organism. While the ants use the plant seeds as a food source, they do not harm the plant. Answer choice B is incorrect because the relationship described between the plant and the native ant species exceeds what would be required by commensalism because both the ant and the plant benefit from their interaction. A commensal relationship requires that only one organism benefit and that the other is not harmed by the interaction; the other organism may receive no benefit. Answer choice C is incorrect because the ants do not attack, kill or eat the plant. Although the ants eat a portion of the plant (the elaisome), this interaction perpetuates the plant’s life cycle.
The question is classified as Recalling / Identifying Accurate Science because this task requires students to recall and identify the types of relationships that exist between organisms interacting within an environment.
The percent of public school students selecting answer choice D for question 3 on the March 2006 Ohio Graduation Test was 43%.
Keywords: ecosystem, biotic, mutualism
Source: Ohio Department of Education July 05