Class 7 Science
Some plants eat insects. Such plants are called insectivorous plants. They trap and digest the insects. Pitcher plant is the example of an insectivorous plant. In pitcher plant the leaf is modified to form a pitcher like structure. The bright colour of the pitcher makes it very attractive to insects. Inside the pitcher; there are several hair-like structures. These hairs direct the trapped insects downwards. When an insect sits on the pitcher of the plant, the lid closes and the insect gets trapped inside the pitcher. The insect is then digested by the enzymes secreted by the cells of the plants.
Cause of eating of insects by plants:
The soil of marshy land is deficient in nitrogen. Plants living in marshy areas do not get nitrogen from the soil. Their nitrogen need is fulfilled by sucking the juice of insects. Venus flytrap, utricularia, drosera and Rafflesia are the other examples of insectivorous plants.
Question 1: What is an insectivorous plant?
Answer: A plant which fulfills its nitrogenous needs by eating insects is called an insectivorous plant.
Question 2: Give an example of insectivores plant?
Answer: Pitcher plant, Venus Fly trap, Bladderwort, Drosera, Rafflesia
Question 3: Why does a plant eat insects?
Answer: Plants living in marshy areas do not get nitrogen from the soil. To fulfill their nitrogenous need, they need to eat insects.
Question 4: Write a brief note on pitcher plants?
Answer: In a pitcher plant, the leaf is modified into a pitcher like structure. The pitcher is complete with a lid. The inside of pitcher is full of hair-like structures. The pitcher is used to trap insects which may fall in it.
Saprtrophs are non-green plants e.g. Agaricus (Mushroom) fungi, yeasts and bacteria. Saprotrophs get their food from dead or decaying organic matters. They grow on decaying organic matters such as cow-dung, wood, bread, etc.
Saprotrophs secrete digestive juice over the decaying materials and absorb nutrients from them. This is called Saprotrophic Mode of Nutrition.
Question 1: What do you understand by saprotrophs?
Answer: An organism which feed on dead and decaying material is called a saprotroph. In this mode of nutrition, digestive enzymes are secreted on the food. The digested food is then absorbed by the organism. In saprotrophs digestion takes place outside the body of the organism.
Question 2: Saprophytes grow in which type of places?
Answer: Saprophytes grow in humid and hot conditions.
Question 3: Give some example of saptrotrophs.
Answer: Mushroom, yeast, toadstool, etc.