Free Ecosystems MCQs with Answers
55 Ecosystems MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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55 questions · page 6 of 6
51. The organisms of the third trophic level are:
- A. Primary consumer
- B. Primary producer
- C. Tertiary consumer
- D. Secondary consumer
Explanation: Secondary consumers belong to trophic level three, they feed on primary consumers.
Correct answer: Secondary consumer52. The ultimate source of energy in an ecosystem is
- A. Photosynthesis
- B. Sun
- C. Plants
- D. Water
Explanation: Sun is the ultimate source of energy because it is the source of most of the energies on Earth. It provides solar energy, it is responsible for photosynthesis in plants and also provides vitamin D to humans.
Correct answer: Sun53. All the food chains and food webs begin with:
- A. Detritus
- B. Herbivores
- C. Green plants
- D. Omnivores
Explanation: The living part of the food chain always begins with plant life, as plants are the only organisms that get their energy from a nonliving source, Sun. We know that the Sun is the ultimate source of energy because it does not depend on anything else.
Correct answer: Green plants54. The change from bare rock or open area is rapid, especially in the initial stages and follows a series of recognizable and hence predictable stages. This process is called
- A. Pioneers
- B. Xerosere
- C. Succession
- D. Secondary succession
Explanation: A broad definition of succession states: 'Ecological succession is the process by which the mix of species and habitat in an area changes over time. Gradually, these communities replace one another until a "climax community" is reached.' (via news.uchicago.edu) This fits the description provided in the question hence it's the correct option.
Correct answer: Succession55. How denitrification does occur in soils?
- A. Bacterial reduction of NO3- ions to N2 gas.
- B. Active uptake of Nitrate ions by plant roots
- C. Drainage of manure from fields
- D. Leaching of nitrate ions
Explanation: Denitrification is a natural soil microbial process where nitrate ions are converted to nitrogen gas which is then lost to the atmosphere. Denitrification occurs when soil bacteria use nitrate for their respiration in place of oxygen in the air.
Correct answer: Bacterial reduction of NO3- ions to N2 gas.