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The World Of Microbes

Class 8th Science Part I Karnataka Board Solution

Exercises
Question 1.

One of the following does not belong to the group
A. Aspergillus niger

B. Clostridium tetani

C. Staphylococcus aureus

D. Vibrio cholerae


Answer:

Out of the given options Aspergillus niger is a fungi whereas the rest three that is Clostridium tetani, Staphylococcus aureus and Vibrio cholerae are bacteria.



Question 2.

The locomotory structure of amoeba is
A. cilium

B. flagellum

C. pseudopodium

D. tentacle


Answer:

Pseudopodia are the temporary cytoplasm filled outgrowth on the surface of an amoeboid cell. These pseudopodia are responsible for the movement of the organism. They also help in feeding and catching of prey. As pseudopodia helps in the movement of organism they are also known as false feet.



Question 3.

Chlorophyll is present in
A. Chlamydomonas

B. Mushroom

C. Yeast

D. Aspergillus


Answer:

Chlamydomonas is unicellular flagellate green algae. Chloroplasts are present in Chlamydomonas which contain the green pigment chlorophyll which is responsible for the conduction of photosynthesis.



Question 4.

Fill in the blanks with suitable words

_________ was considered father of microbiology.


Answer:

The study of microscopic organisms such as bacteria, fungi, protozoa and viruses is known as microbiology. For the first time bacteria and other microorganisms were observed by Antonie Philips van Leeuwenhoek that is why Antonie Philips van Leeuwenhoekis considered as the father of microbiology.



Question 5.

Fill in the blanks with suitable words

Malaria is caused by _________ .


Answer:

Malaria is caused by plasmodium. Plasmodium is the malarial parasite which is transmitted through the female anopheles mosquito. Different species of plasmodium cause different kind of malaria like Plasmodium falciparum which cause malignant malaria which is considered to be fatal.

Taxonomically, plasmodium is a protozoan which comes under kingdom Protista.



Question 6.

Fill in the blanks with suitable words

Vibrio is ______________ shaped bacteria.


Answer:

Vibrio is the comma shaped bacteria. According to their shape bacteria can be divided into many categories. The round bacteria are known as coccus, rods shaped are known as bacilli, spiral are known as spirilla, similarly comma shaped bacteria are known as vibrio.



Question 7.

Answer the following

What are microorganisms?


Answer:

Microorganisms are the smallest organisms which are visible only through microscope and not visible through naked eyes. They are also known as microbes.

They may exist solitary (in their single celled state) or in their colonies. Study of microbes is known as microbiology.


Examples of some microbes include bacteria, viruses, Chlamydomonas (algae) or yeast (fungi).




Question 8.

Answer the following

Explain the structure of a typical bacillus?


Answer:

Bacteria are the smallest microorganisms present everywhere on the Earth and thus considered as cosmopolitan. They have a unique structure because of which they can resist high temperature and high pH.


● CAPSULE: This is the thick protective covering present on certain bacteria. The capsule is made up of polysaccharides. It protects the bacteria from drying out.


● CELL WALL: Cell wall of typical bacteria is made up of peptidoglycan, a protein- sugar complex. It gives the bacteria the perfect shape and provides support and rigidity. It contains pili and flagella which help in movement and anchorage.


● CELL MEMBRANE: It is the universal membrane present in all the cells. It is selectively permeable in nature. It controls the movement of substances in and out of the cell.


● CYTOPLASM: It is the main place where all the important functions of bacteria take place. It is a gel like matrix composed of water, enzymes and nutrients. It also contains cell structures like ribosomes, chromosomes and plasmids.


● FLAGELLA: They are the hair like structures which help in locomotion. Bacteria can be of many types depending upon the number of flagella and the type of flagella present.


● PILI: They are the hair like projections present on the surface of bacteria. They are usually many in number and are small as compared to flagella. They usually help in attachment. Specialized pili like sex pili are used for conjugation.


● NUCLEOID: This is the region where the chromosomal DNA is located. Bacteria do not have a membrane bound nucleus but simply an area where DNA strands are present. Most of the bacteria have a single, circular chromosomal DNA.


● RIBOSOMES: They are also known as the ‘protein factories’ of the cell. In bacteria, the ribosomes are of 70s type. They translate the genetic code from molecular language to amino acids.



Question 9.

Answer the following

Draw a diagram of a typical bacillus and label the parts?


Answer:



Question 10.

Answer the following

How can the transmission of cholera be prevented?


Answer:

Cholera disease is spread through the bacteria Vibrio cholerae. They are the comma shaped bacteria having a long flagella for propagation. The bacteria for cholera are usually found at the places where water is contaminated by faeces.

Transmission of cholera can be prevented by:-


1) Taking care of proper hygiene like washing hands with soap and clean water after defecation.


2) It can also be prevented by use of proper toilets


3) Having proper sanitation and sewage.


4) Intake of clean food materials.




Question 11.

Answer the following

What are vaccines?


Answer:

Vaccines are substances which are injected to a person. It consists of killed or weakened pathogens (disease causing microorganisms). They are introduced in the body of human beings at a very early age. This weakened pathogens cause very mild harm to the body in result of which the body produces antibodies against that pathogen. Whenever the same pathogen enters our body, the body produces exaggerated reaction in response to the pathogen.

The principal behind vaccination is that whenever a microorganism enters in a body, the defense mechanism of that particular body gets activated and it starts producing antibodies against that particular pathogen. Even after the pathogen is removed out from the body, the body will always remember to produce those particular antibodies against that pathogen. If that particular pathogen encounters with the body once again, the body will now show exaggerated response and will produce antibodies very quickly against that pathogen.


So in vaccination, a weak and dead form of some pathogen is introduced in the body so that the body will produce antibodies against it and when actual infection will occur, it can easily respond against it to protect the body and thus body will get immunized.