Class 8 Test 1 Science

A termite is not considered a microorganism because it is a multicellular organism, whereas microorganisms are single-celled organisms. Bacteria, fungi, and protozoa are all examples of microorganisms as they are single-celled and can only be seen under a microscope. Termite, on the other hand, is a complex organism with specialized cells and organ systems, making it distinct from microorganisms.

Pathogens are microorganisms such as bacteria, viruses, fungi, or parasites that can cause diseases in humans, animals, and plants. They invade the host's body and disrupt normal bodily functions, leading to illness. Preys are organisms that are hunted and killed by other organisms, and they do not directly cause diseases. Antibiotics are medications used to treat bacterial infections, and antibodies are proteins produced by the immune system to help fight off infections. While both antibiotics and antibodies are involved in the body's defense against pathogens, they do not cause diseases themselves.

Algae is the correct answer because it is a group of microorganisms that contain chlorophyll and are capable of photosynthesis. Chlorophyll is a pigment that allows organisms to convert sunlight into energy through the process of photosynthesis. Algae can be found in various aquatic environments, such as oceans, lakes, and ponds. They play a vital role in the ecosystem by producing oxygen and serving as a food source for other organisms. Bacteria, fungus, and viruses are not chlorophyllous and do not possess the ability to carry out photosynthesis.

When a microbe enters the body, the immune system responds by producing antibodies. These are proteins specifically designed to recognize and bind to antigens on the microbe, which are unique molecules that trigger the immune response. Once bound, antibodies can neutralize the microbe, mark it for destruction by other immune cells, or prevent it from entering cells. This process is crucial for protecting the body against infections and diseases.

Finrot disease is a common ailment that affects fish. It is caused by bacteria or fungi that infect the fish's fins and tail, leading to deterioration and rotting of the affected areas. This disease is specific to fish and does not affect other organisms such as eagles, elephants, or hens. Therefore, the correct answer is Fish.

Immunising is not a method of food preservation because it refers to the process of administering vaccines to stimulate the immune system and protect against diseases. It is not a technique used to preserve food and extend its shelf life. Canning, freezing, and dehydrating, on the other hand, are commonly used methods of food preservation that involve various techniques to prevent spoilage and maintain the quality of food for longer periods.

The correct answer is Bacterium because Citrus Canker is caused by a bacterial infection. It is caused by the bacterium Xanthomonas citri subsp. citri, which affects citrus trees and causes raised corky lesions on the leaves, stems, and fruit. This bacterium is highly contagious and can be spread through wind, rain, and contaminated tools or equipment. Control measures for Citrus Canker include pruning infected branches, applying copper-based sprays, and practicing good sanitation to prevent the spread of the bacterium.

Diatoms are a type of algae. They are single-celled organisms that belong to the group of photosynthetic protists known as algae. Diatoms are characterized by their unique cell walls made of silica, which give them a glass-like appearance. They are found in various aquatic environments, including oceans, lakes, and rivers. Diatoms play a crucial role in the ecosystem as primary producers, converting sunlight into energy through photosynthesis. They are an essential food source for many aquatic organisms and are also used in various industries, including water filtration and biofuels.

Chlamydomonas is not a protozoa because it is a type of green algae. Protozoa are single-celled organisms that belong to the kingdom Protista, while Chlamydomonas belongs to the kingdom Plantae. Protozoa are characterized by their ability to move using specialized structures like cilia, flagella, or pseudopodia, whereas Chlamydomonas moves using two flagella. Therefore, Chlamydomonas does not fit the criteria to be classified as a protozoa.

Tetanus is caused by the bacterium Clostridium tetani. This bacterium is commonly found in soil, dust, and animal feces. It enters the body through a wound or cut and produces a toxin called tetanospasmin, which affects the nervous system. The toxin causes muscle stiffness and spasms, leading to the characteristic symptoms of tetanus, such as lockjaw and muscle rigidity. Prompt medical treatment, including vaccination and wound care, is essential to prevent and treat tetanus infection.