This is the content of the pop-over!





ILTS Biology (105) Practice Tests & Test Prep by Exam Edge - Free Test


Our free ILTS Science Biology (239) Practice Test was created by experienced educators who designed them to align with the official Illinois Licensure Testing System content guidelines. They were built to accurately mirror the real exam's structure, coverage of topics, difficulty, and types of questions.

Upon completing your free practice test, it will be instantly reviewed to give you an idea of your score and potential performance on the actual test. Carefully study your feedback to each question to assess whether your responses were correct or incorrect. This is an effective way to highlight your strengths and weaknesses across different content areas, guiding you on where to concentrate your study efforts for improvement on future tests. Our detailed explanations will provide the information you need to enhance your understanding of the exam content and help you build your knowledge base leading you to better test results.

Login or Create an Account to take a free test

After you have completed your free test you will receive a special promo code that will save your between 10-15% on any additional practice tests!


** Sample images, content may not apply to your exam **


Additional test information
Back To General Exam Info

ILTS Science Biology - Free Test Sample Questions

Which of the following best describes the principle of competitive exclusion?





Correct Answer:
two species cannot share the same niche within a habitat.


the principle of competitive exclusion, also known as gause's law, states that two species competing for the exact same resources cannot stably coexist if other ecological factors remain constant. when two species vie for the same niche, one species will outcompete the other, leading either to the extinction of the less competitive species or to an evolutionary or behavioral shift toward a different ecological niche.

the core idea behind this principle is that each species has its own set of natural advantages and adaptations that allow it to thrive in particular environmental niches. niches are multidimensional, including not just the physical space a species occupies but also its role in the ecosystem, such as what it eats, where it lives, and how it interacts with other species. when two species try to occupy the same niche, they compete for the same resources (food, space, etc.), which are limited.

the outcome of this competition is determined by which species can use the resources more efficiently. over time, the less efficient competitor will either adapt to a different niche, migrate to a different area, or face extinction. this principle has been observed in many ecological studies and has significant implications for understanding biodiversity and the organization of communities in nature.

in practical terms, the principle of competitive exclusion is important for conservation efforts, resource management, and understanding the impacts of invasive species. it helps explain why certain invasive species can dramatically alter existing ecosystems by outcompeting native species for their niches, leading to shifts in the community structure and sometimes to the extinction of native species.

therefore, the correct answer that "two species cannot share the same niche within a habitat" encapsulates the essence of the competitive exclusion principle by emphasizing the impossibility of coexistence within the same niche without evolutionary or ecological changes.