Worksheet-2: The Invisible Living World: Beyond Our Naked Eye | Science Class 8 PDF Download

Multiple Choice Questions (MCQs)

Q1: Which of the following is not a use of microorganisms?

A) Making antibiotics

B) Fixing nitrogen in the soil

C) Increasing the spoilage of food

D) Producing alcohol

Q2: Which microorganism is used to make curd from milk?

A) Yeast

B) Lactobacillus

C) Penicillium

D) Rhizobium

Q3: What is the role of microorganisms in the nitrogen cycle?

A) They decompose organic matter releasing nitrogen gas into the atmosphere.

B) They convert atmospheric nitrogen into usable compounds for plants.

C) They increase the nitrogen content in the atmosphere.

D) They consume nitrogen from the soil.

Q4: How do friendly microorganisms benefit humans?

A) They cause diseases.

B) They help in digestion and nutrient absorption.

C) They spoil food.

D) They reduce soil fertility.

Fill in the Blanks

Q1: Microorganisms that are beneficial to humans and aid in digestion are called__________ microorganisms.

Q2: The process by which yeast helps to make bread is called ____________.

Q3: The foldable, low-cost paper microscope developed to study microorganisms is known as a ____________.

Q4: Rhizobium bacteria are known for fixing nitrogen in the soil, which helps ____________ plants.

True/False Questions

Q1: Microorganisms can only be harmful and have no beneficial uses.

Q2: All bacteria are harmful to humans and other living organisms.

Q3: Preservation by sugar involves reducing the moisture content which inhibits bacterial growth.

Very Short Answer Questions

Q1: What are preservatives?

Q2: Name the microorganisms which can fix atmospheric nitrogen in the soil.

Q3: Give two examples of algae.

Q4: What are the harmful effects of microorganisms on plants?

Q5: How are jams and squashes preserved?

Q6: How can food be preserved by adding oil and vinegar?

You can access the solutions to this worksheet here.