CBSE Class 7 Answered

Salim is a farmer who always prefers to use organic manure in his field. But his friends insist him to apply fertilizers where he can get more profit within a short period of time. In which aspects are manures better than fertilizers? Write any two values which can be adopted from Salim. (5) How dodders draw its nutrients from the host? (3) Write the difference between autotrophic and heterotrophic nutrition. (3) Classify the different types of heterotrophic nutrition. Write in brief about any one type. (5) In general, compare the modes of saprophytic and parasitic nutrition. (5)

Asked by Nimmi | 04 May, 2018, 12:26: PM

Expert Answer

1. Manures increase soil fertility thereby retaining the water holding capacity and absorption rate which do not cause pollution. In the other hand, fertilisers which do contain important minerals do not mix completely in the soil thereby causing pollution of soil and water. It also leads to toxication of ecosystem.

Two values adopted from Salim can be: organic farming tradition is well maintained and he is very particular about his irrigation techniques which yields better results

2. Dodder is a parasitic flowering plant which uses parasitic mode of nutrition. The dodder’s seed germinates, forming an anchoring root, and then sends up a slender stem that grows in a spiral way until it reaches the host plant. It then coils around the stem of the host plant and throws out haustoria, which penetrate it. Water is drawn through the haustoria from the host plant's stem and xylem, and nutrients are drawn from its phloem.

Autotrophic Nutrition	Heterotrophic Nutrition
The organism prepares its food from simple substances present in the surroundings	The organism obtains food from digesting organic compounds.
Autotrophic nutrition is mainly of two types -photoautotrophic and chemo autotrophic nutrition.	Heterotrophic nutrition may be holozoic, saprozoic, parasitic, etc.
Autotrophs depend directly on solar energy	Heterotrophs depend indirectly on solar energy.
CO₂ is taken in and O₂ is released	Food is taken into body and undigested food is released outside of the body.

4. There are three types of heterotrophic nutrition- saprophytic, parasitic and holozoic.

Holozoic nutrition is the process of obtaining nourishment by the ingestion of complex organic material, which is then digestde and absorbed.

In this nutrition, parts of plants or animals or an organism as a whole is ingested and then digested. Here, animals take the energy containing organic materials, called food, into the gut. After digestion, this food can be absorbed into the body. When this food is decomposed in oxidation reactions, it can release energy to supply for daily uses.

5. The mode of nutrition in which an organism obtains nutrients from dead and decaying organic matter is called saprophytic nutrition. Example - Rhizopus (bread mould), Mucor (pin mould), Yeast, Agaricus (mushroom) .

Parasites have heterotrophic mode of nutrition. They live outside or inside of the body of the host and derive its nutrition which cause harm to the host. Example- Plasmodium

Answered by Sivanand Patnaik | 05 May, 2018, 10:37: AM

CBSE Class 7 Answered

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