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MICROORGANISMS : FRIEND AND FOE

🎓 Class 8📖 Science📖 8 notes🧠 15 Q&A⏱️ ~12 min

MICROORGANISMS : FRIEND AND FOEStudy Notes

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Microorganisms

Explanation

Microorganisms

Microorganisms, also known as microbes, are tiny living organisms that are too small to be seen with the naked eye. They can be unicellular or multicellular and include bacteria, fungi, protozoa, algae, and viruses. Microorganisms are found everywhere—in soil, water, air, and even inside the human body. Despite their small size, they play a crucial role in various natural processes and human life. They can be both beneficial and harmful. For example, some microorganisms help in digestion, while others cause diseases. They reproduce rapidly and can adapt to different environments. The study of microorganisms is essential for understanding health, disease, agriculture, and industry. This section introduces the basic concept of microorganisms, their types, and their significance.

  • Microorganisms are tiny living organisms invisible to the naked eye.
  • They include bacteria, fungi, protozoa, algae, and viruses.
  • Found everywhere: soil, water, air, and inside living beings.
  • Can be both beneficial (e.g., digestion) and harmful (e.g., diseases).
  • Reproduce rapidly and adapt to various environments.
  • Important for health, agriculture, and industry.
  • 📌 Microorganisms: Tiny living organisms not visible to the naked eye.
  • 📌 Bacteria: Single-celled microorganisms without a defined nucleus.
  • 📌 Fungi: Organisms that include molds and yeasts, some of which are multicellular.

Where do Microorganisms Live?

Explanation

Where do Microorganisms Live?

Microorganisms are found in almost every habitat on Earth. They live in soil, water, air, inside plants, animals, and humans. Some microorganisms can survive in extreme environments such as hot springs, deep ocean vents, and polar ice. Their ability to adapt to various conditions makes them ubiquitous. For example, bacteria are present in the soil where they help in decomposing organic matter. Algae grow in water bodies and perform photosynthesis. Some microorganisms live inside the human body and form part of the normal flora, aiding in digestion and protecting against harmful microbes. This section explains the diverse habitats of microorganisms and their adaptability, highlighting their importance in ecosystems and human health.

  • Microorganisms inhabit soil, water, air, plants, animals, and humans.
  • Some survive in extreme environments like hot springs and polar ice.
  • Soil bacteria help decompose organic matter.
  • Algae perform photosynthesis in water bodies.
  • Normal flora in humans aid digestion and protect against pathogens.
  • Their adaptability makes them ubiquitous.
  • 📌 Normal flora: Microorganisms living harmlessly inside the human body.
  • 📌 Decomposition: Breakdown of dead organic matter by microorganisms.
  • 📌 Photosynthesis: Process by which green plants and algae make food using sunlight.

Are Microorganisms Useful?

Explanation

Are Microorganisms Useful?

Microorganisms are extremely useful to humans and the environment. They play a vital role in processes such as decomposition, nitrogen fixation, and food production. Decomposers like bacteria and fungi break down dead plants and animals, returning nu

Practice QuestionsMICROORGANISMS : FRIEND AND FOE

15 practice questions with detailed answers

Q1.Which of the following is NOT a type of microorganism?
A.A) Bacteria
B.B) Algae
C.C) Protozoa
D.D) Insects

Answer:

Insects

Explanation:

Microorganisms include bacteria, fungi, protozoa, algae, and viruses. Insects are multicellular animals and are not microorganisms.

Easy
Q2.Microorganisms are too small to be seen with the naked eye because they are usually _____ in size.

Answer:

microscopic / microscopic size

Explanation:

Microorganisms are microscopic, meaning they are so small that they cannot be seen without the aid of a microscope.

Easy
Q3.Which microorganism is responsible for nitrogen fixation in the soil?
A.A) Rhizobium
B.B) Amoeba
C.C) Yeast
D.D) Influenza virus

Answer:

Rhizobium

Explanation:

Rhizobium bacteria live in root nodules of leguminous plants and convert atmospheric nitrogen into forms usable by plants, a process called nitrogen fixation.

Medium
Q4.Which of the following diseases is caused by a protozoan microorganism?
A.A) Malaria
B.B) Tuberculosis
C.C) Athlete's foot
D.D) Common cold

Answer:

Malaria

Explanation:

Malaria is caused by the protozoan parasite Plasmodium, transmitted by mosquitoes.

Medium
Q5.What is the main role of yeast in bread making?

Answer:

Yeast is a fungus that ferments sugars in the dough to produce carbon dioxide gas. This gas forms bubbles that make the dough rise and become soft and spongy. For example, yeast helps in the preparation of bread by causing fermentation.

Explanation:

Yeast ferments the sugars present in the dough, producing carbon dioxide which causes the dough to rise. This process is essential for the texture and volume of bread.

Medium
Q6.How do bacteria help in the process of decomposition?

Answer:

Bacteria act as decomposers by breaking down dead plants and animals into simpler substances. This process returns nutrients to the soil, which helps plants to grow. For example, bacteria decompose fallen leaves and dead animals in the soil.

Explanation:

Decomposer bacteria break down complex organic matter into simpler inorganic substances, recycling nutrients in the ecosystem.

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Q7.Which of the following is NOT a habitat where microorganisms can be found?
A.A) Soil
B.B) Water
C.C) Air
D.D) Outer space

Answer:

Outer space

Explanation:

Microorganisms are found in soil, water, air, and inside living organisms. Outer space is an extreme environment where microorganisms cannot survive naturally.

Easy
Q8.Explain how microorganisms inside the human body can be beneficial.

Answer:

Microorganisms inside the human body, known as normal flora, help in digestion by breaking down food substances. They also protect the body by preventing harmful microbes from growing. For example, beneficial bacteria in the gut aid in digestion and keep harmful bacteria in check.

Explanation:

Normal flora microbes assist digestion and protect against infections by competing with harmful microorganisms.

Medium