CBSE Class 9 Answered

1. Parasitic nutrition or parasitism is a mode of heterotrophic nutrition where an organism (known as a parasite) lives on the body surface or inside the body of another living organism (known as a host). The parasite obtains nutrition directly from the body of the host. Since these parasites derive their nourishment from their host, this symbiotic interaction is often harmful to the host. Parasites are dependent on their host for survival since the host provides nutrition and protection. E.g. tapeworms, fleas, and barnacles.

2. Commensalism is a type of symbiotic relationship between two organisms wherein one organism benefits without affecting the other. E.g. hermit crabs use gastropod shells to protect their bodies.

3. Saprophytic nutrition is a kind of nutrition in which organisms obtain their food from dead and decaying organic matter. The saprophytic organisms convert complex organic matter to simpler compounds. They help in recycling the natural compounds in nature and also clean the environment. E.g. Agaricus (mushroom), some fungi, some bacteria, etc.

4. Symbiotic relationship or Symbiosis is a mutually beneficial association existing between two organisms in which both the organisms derive benefit from each other without causing any harm to each other. E.g. leguminous plants show symbiotic mode of nutrition. Alga and fungus live together. Fungus provides water and shelter to the alga. In return, alga provides food prepared by photosynthesis.