Basic Science Solutions for Class 8 Science Chapter 3 Microorganisms are provided here with simple step-by-step explanations. These solutions for Microorganisms are extremely popular among class 8 students for Science Microorganisms Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of class 8 Science Chapter 3 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Basic Science Solutions. All Basic Science Solutions for class 8 Science are prepared by experts and are 100% accurate.

Page No 37:

Answer:

The study of microorganisms is called as microbiology.

Page No 37:

Answer:

Some microorganisms survive unfavourable conditions by forming spores in which they remain in inactive form until the conditions become favourable for them.

Page No 37:

Answer:

Sargasso Sea owes its name to the brown alga Sargassum.

Page No 37:

Answer:

Groups of bacteria are:

(i)   Bacilli (rod-shaped)
(ii)  Cocci (spherical)
(iii) Spirilla (spiral-shaped)
(iv) Vibrios (comma-shaped)

Page No 37:

Answer:

Bacterial cells Cells of other organisms
They do not have a nucleus. They have a prominent nucleus.

Page No 37:

Answer:

Bacteria reproduce through binary fission, a type of asexual reproduction. In this method, one cell divides into two.

Page No 37:

Answer:

Uses of bacteria:

(i) Some of them are used in producing antibiotics.
(ii) Some of them are used in making yoghurt and cheese from milk.

Page No 37:

Answer:

Yes, red and brown algae have chlorophyll but the green colour is masked by other additional pigments.

Page No 37:

Answer:

Euglena is a protozoan that contains chlorophyll and can photosynthesise.

Page No 37:

Answer:

Amoebiasis is caused by Entamoeba histolytica, which is a protozoan.

Page No 37:

Answer:

Diatoms are a group of algae found in fresh water and marine habitats. Their cell walls are made of silica. Diatoms accumulate at the bottom of lakes, rivers and seas when they die. The silica on their bodies is used to make glass, porcelain, ceramics, toothpaste, polishes and filters.

Page No 37:

Answer:

Following are the uses of Algae:

(i) Algin is a gummy substance. It is obtained from kelp and is used to thicken ice creams, cosmetics and shaving creams.
(ii) Agar is obtained from red algae. It is used in laboratories for making cultures of tissues and microorganisms.
(iii) Some of them are served as food in China and Japan.

Page No 37:

Answer:

Paramecium has hair-like projections called cilia. Cilia help Paramecium to move in the soil and swim in water. It also help Paramecium to feed by directing the food and water into its oral groove.

Page No 37:

Answer:

Protozoans present in termites digest the cellulose in the wood that is eaten by them and convert it into carbohydrates.
Bacteria living in our intestines help in the absorption of food and protect us from certain diseases.

Page No 37:

Answer:

Following are the ways in which fungi harm us:

(i) They cause infections of the skin.
(ii) If food containing carbohydrate is kept in a warm and moist place, it is destroyed by moulds.

Page No 37:

Answer:

Excessive growth of algae in water bodies harms the other aquatic animals. When the water bodies are enriched by plant nutrients, it causes rapid growth of algae. Soon, algae form a thick layer over the surface of the water body, called algal bloom, which deprives the other aquatic organisms of light and oxygen. They reduce the oxygen content of the water and cause the death of other aquatic organisms. This is called as eutrophication.

Page No 37:

Answer:

Uses of fungi:

(i) Some of them such as mushrooms are edible.
(ii) Moulds are used to add flavour to processed cheese.
(iii) Yeast is used in making bakery products and to ferment fruit juices and alcoholic drinks. They produce carbon dioxide while respiring that makes bread and buns to rise and become fluffy.

Page No 37:

Answer:

Viruses are considered as something between the living and non-living because they do not grow or reproduce by themselves. This makes them non-living. However, when a virus enters a living cell of an organism, it obtains energy from the host cell and starts reproducing. This makes them living, as reproduction is an important characteristic of living organisms.
Viruses multiply within a host cell by destroying the nuclear material of the host cell and direct it to produce the copies of virus. This finally bursts the host cell and releases the viruses that infect other cells.

Page No 37:

Answer:

1. The tangled mass of threadlike structures formed by moulds is called mycelium.
2. Blue-green algae are now called cyanobacteria because they are more like bacteria.
3. Protozoans form the link in the food chain between algae and small aquatic organisms.
4. Protozoa means 'the first animal'.
5. Sugarfermentationcarbon dioxide+alcohol.
6. The spore case of moulds is called sporangia.

Page No 37:

Answer:

(c) mould

Pencillin is obtained from certain moulds.

Page No 37:

Answer:

(a) spore

Lower plants and plantlike organisms reproduce by producing a single cell in a tough membrane called spore.

Page No 37:

Answer:

(b) algae

Algin is obtained from algae.

Page No 37:

Answer:

(d) diatoms

Cell walls of diatoms are rich in silica and form seabeds by the deposited silica at the bottom of the sea.

Page No 37:

Answer:

(a) bacteria

Some bacteria are present in the roots of leguminous plants. They convert nitrogen of the air to nitrates.



View NCERT Solutions for all chapters of Class 8