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Microorganisms and Environmental Balance

Biology

This text describes the crucial roles microorganisms play in maintaining environmental balance, focusing on their involvement in food webs, nutrient cycling (especially nitrogen), and regulating oxygen and carbon dioxide levels. It details processes like decomposition, nitrification, and denitrification, highlighting how bacteria and fungi contribute to recycling elements and supporting plant life.

Microbiology Ecology Biogeochemical Cycles
24 Questions Medium Ages 12+ Feb 24, 2026

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About this Study Set

This study set covers Biology through 24 practice questions. This text describes the crucial roles microorganisms play in maintaining environmental balance, focusing on their involvement in food webs, nutrient cycling (especially nitrogen), and regulating oxygen and carbon dioxide levels. It details processes like decomposition, nitrification, and denitrification, highlighting how bacteria and fungi contribute to recycling elements and supporting plant life. Every question includes the correct answer so you can learn as you go — pick any format above to get started.

Questions & Answers

Browse all 24 questions from the Microorganisms and Environmental Balance study set below. Each question shows the correct answer — select a study format above to practice interactively.

1 What process is described as 'deritrification by cenitifying bacteria' in the text?
  • A Conversion of nitrates to free nitrogen
  • B Conversion of free nitrogen to nitrates
  • C Breakdown of dead organic matter
  • D Production of organic nutrients
2 Which of the following are roles of microorganisms in maintaining environmental balance?
  • A Electrical fixation of nitrogen
  • B Acting as producers and decomposers
  • C Causing plant diseases
  • D Producing atmospheric electricity
3 Autotrophic bacteria and algae are described as playing what role in the food chain?
  • A Decomposers
  • B Consumers
  • C Producers
  • D Pathogens
4 What is the primary function of decomposition bacteria, saprophytic fungi, and protists in the environment?
  • A To convert ammonia into nitrites
  • B To break down dead organic matter
  • C To fix free nitrogen into the atmosphere
  • D To absorb nutrients from the soil
5 Which elements are recycled in the environment and made available for plant uptake through decomposition?
  • A Oxygen and Hydrogen
  • B Carbon, Nitrogen, Phosphorus, and Sulfur
  • C Iron and Potassium
  • D Calcium and Magnesium
6 Nodule bacteria and free-living bacteria contribute to the nitrogen cycle by converting free nitrogen into what?
  • A Ammonia
  • B Urea
  • C Nitrates
  • D Nitrites
7 Nitrifying bacteria are responsible for converting ammonia into nitrites and then into what, which plants can absorb?
  • A Free nitrogen
  • B Nitrates
  • C Organic matter
  • D Proteins
8 Denitrifying bacteria convert ammonia and nitrates into what, returning it to the atmosphere?
  • A Oxygen
  • B Carbon dioxide
  • C Water vapor
  • D Free nitrogen
9 How do autotrophic bacteria and algae help maintain the balance between oxygen and carbon dioxide?
  • A By releasing carbon dioxide and absorbing oxygen
  • B By absorbing carbon dioxide and releasing oxygen during photosynthesis
  • C By breaking down organic matter
  • D By converting nitrates to free nitrogen
10 What percentage of oxygen produced by photosynthesizing organisms is attributed to algae?
  • A 10%
  • B 25%
  • C 53%
  • D 75%
11 The diagram shows that dead organic matter can be converted to ammonia via decomposition and then to nitrites and nitrates through nitrification.
  • A True
  • B False
12 What is the structure of Rhizopus shown in the diagram?
  • A A bacterium
  • B A fungus
  • C An alga
  • D A protist
13 Rhizoids are a part of the structure of Rhizopus, anchoring it to the substrate.
  • A True
  • B False
14 Spores are involved in the reproduction of Rhizopus.
  • A True
  • B False
15 What is the role of 'electrical fixetii Gy ightning ancd rain' mentioned in the text?
  • A It converts free nitrogen to nitrates.
  • B It breaks down dead organic matter.
  • C It contributes to nitrogen fixation in the atmosphere.
  • D It is a process of denitrification.
16 The diagram illustrates how animal excretion (urine) leads to the formation of urea, which is then converted to ammonia.
  • A True
  • B False
17 Which of the following is a type of bacteria involved in the nitrogen cycle, as mentioned in the text?
  • A Decomposition bacteria
  • B Saprophytic fungi
  • C Nodul bacteria
  • D Slime moulds
18 What is a sporangium?
  • A A structure for absorbing nutrients
  • B A reproductive vessel containing spores
  • C A root-like structure
  • D A type of leaf
19 A sporangiophore is a stalk that bears a sporangium.
  • A True
  • B False
20 Free-living soil bacteria are mentioned as playing a role in the nitrogen cycle.
  • A True
  • B False
21 The process of converting ammonia into nitrites and then nitrates is called nitrification.
  • A True
  • B False
22 Protists like slime moulds are mentioned as having a role as:
  • A Producers
  • B Decomposers
  • C Nitrifiers
  • D Denitrifiers
23 Plants absorb nitrates from the soil through their roots.
  • A True
  • B False
24 The text mentions 'food' in relation to the breakdown of dead organic matter and nutrient cycling.
  • A True
  • B False
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