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Q.8 Write a short paragraph on the harmful effects of microorganisms.

Answer :

Microorganisms cause diseases in both plants and animals. A microbe which is capable of causing infectious disease in an animal or plant is called a pathogen. Four groups of microbes contain pathogens: bacteria, fungi, protozoa and the viruses.


1. Bacteria causes toxicity as it produce toxins which can damage specific tissues in the body.
2. Bacteria shows invasiveness as it multiplies rapidly at the site of infection and overwhelm the body's defense mechanisms.
3. Bacteria can cause diseases in humans, such as cholera, diphtheria, dysentery, bubonic plague, pneumonia, tuberculosis (TB), typhoid, food poisoning etc.


1. Fungi create harm by spoiling food, destroying timber, and by causing diseases of crops, livestock, and humans.
2. Penicillium and Aspergillus, spoil many stored foods.
3. Fungi cause the majority of plant diseases, which in turn cause serious economic losses.


1. It causes many deadly human diseases such as sleeping sickness, amoebic dysentery, and malaria.
2. They also cause disease in plants. Phytomonas, a type of protozoa that is transmitted as durable zoospores that survive in a resting state in the soil for many years and further they transmit plant viruses.


1. Some viruses can cause lifelong or chronic infections where the viruses continue to reproduce in the body despite the host's defense mechanisms. For e.g., AIDS
2. Most plant viruses are transmitted by insect vectors that cause damage to the plant.
3. It causes chickenpox, flu (influenza), herpes etc., in humans while it causes tobacco mosaic virus(TMV) and many other diseases in plants.

Though algae doesn't cause diseases but it also harms our environment and aquatic life in many ways:


1. Algal blooms can reduce the ability of fish and other aquatic life to find food and can cause entire populations to leave an area or even die.
2. Nutrient pollution fuels the growth of harmful algal blooms which have negative impacts on aquatic ecosystems.

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