Maharashtra Board Class 7 Science Cell Structure and Microorganisms Textbook BackPage Exercises which includes Fill in the blanks ,Question Answers and Extra Question and Answers from the Chapter.
Fill in the blanks with the proper word.
- The organelle called the chloroplast is present in plant cells only.
- Garbage is converted into manure by micro-organisms.
- In the cell, photosynthesis is carried out with the help of chloroplasts.
- An electron microscope is necessary for the study of cell organelles.
Answer the following questions.
What is a ‘cell’ ?
A ‘cell’ is the basic structural and functional unit of all living organisms. It is the smallest unit of life and the building block of complex organisms.
Name the different organelles in a cell ?
Different organelles in a cell include the nucleus, endoplasmic reticulum, Golgi bodies, lysosomes, mitochondria, vacuoles, plastids (plant cells), cell wall (plant cells), plasma membrane (animal cells), and cytoplasm.
What are micro-organisms ?
Micro-organisms are tiny, living organisms that are too small to be seen with the naked eye. They can only be observed under a microscope. These organisms include bacteria, viruses, fungi, protozoa, and algae.
Which are the different types of micro-organisms ?
The different types of micro-organisms include Bacteria, Viruses, Fungi, Protozoa, Algae.
Give reasons.
Diseases spread on a large scale during periods of heavy rainfall and floods.
Floods and heavy rainfall spread diseases because:
- Water sources can become contaminated with sewage and pathogens due to heavy rainfall and flooding.
- Disease-carrying vectors like mosquitoes and flies may spread in flood waters.
- Overcrowding in temporary shelters during floods can spread diseases.
There is a possibility of food poisoning if we eat stale food.
Stale food can cause food poisoning because:
- Food that is stale can produce harmful toxins that can cause food poisoning.
- Keeping food for a long time increases the risk of bacterial contamination.
Soil is turned over during tilling.
When plowing, soil is turned because:
- Using tillage breaks up compacted soil and improves aeration, so plants can access oxygen, water, and nutrients easier.
- It promotes plant growth and crop production by mixing organic matter and nutrients evenly.
Fungus grows quickly in moist or humid conditions.
In moist or humid conditions, fungi grow rapidly:
- Moisture is required for fungi to grow.
- Humidity is ideal for spore germination and fungal growth.
- Organic matter is broken down by fungi and nutrients are obtained.
A refrigerator is used in almost every home.
Every household uses a refrigerator for:
- Low temperatures prevent microorganism growth and reproduction in food, which helps prevent spoilage.
- Additionally, they inhibit enzymes that spoil food.
- Refrigeration reduces chemical degradation and microbial growth of perishable foods.
Bread ‘rises’ during baking.
During baking, bread rises because:
- By fermenting sugars in bread dough, yeast produces carbon dioxide gas.
- The carbon dioxide trapped in the flour causes the dough to rise, making the bread airy and light.
Fodder is soaked in water before offering to cattle.
Water is added to fodder before feeding to cattle for:
- Adding water to fodder increases its moisture content, making it easier to digest.
- By breaking down antinutrition compounds, it can enhance the nutritional value of fodder.
