Class 7 Science Chapter 1 MCQ

Photosynthesis also takes place in other green parts of the plant — in green stems and green branches. The desert plants have scale- or spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.

The bodies of living organisms are made of tiny units called “cells”. Cells can be seen only under the microscope. Some organisms are made of only one cell. The cell is enclosed by a thin outer boundary, called the “cell membrane”.

Saprophytic nutrition is scene in yeast, mushroom and bread mould. In this mode of nutrition, organisms obtain their food from dead and decaying organic matter. Such organisms are known as saprophytes.

These organisms (yeast, mushrooms and bread-mould) are called “fungi”. They have a different mode of nutrition. They secrete digestive juices on the dead and decaying matter and convert it into a solution. Then they absorb the nutrients from it. This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called “saprotrophic nutrition”. Plants which use saprotrophic mode of nutrition are called “saprotrophs”.

Chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis. During the process oxygen is released. The carbohydrates ultimately get converted into starch. The presence of starch in leaves indicates the occurrence of photosynthesis. The starch is also a carbohydrate.

Statement [A] is correct. All green plants are autotrophs. They can make their own food from simple substances like CO2 and H2O by the process of photosynthesis. Oxygen gas produced during this process is liberated into the air. The other statements in correct form are: Most animals are heterotrophs and CO2 is essential for photosynthesis.

Generally, leguminous plant such as gram, pulses. These plants have root nodules in them which have a symbiotic association with rhizobium bacteria. It converts nitrogen gases as compounds. In return, the plants provide food and shelter to the bacteria. Hence, farmers do not need to apply nitrogenous fertilizers in the field during cultivation.

Plants synthesise their food with the help of chlorophyll. It helps to capture the energy of Sunlight. Plants get raw materials form surroundings. So, we find that sunlight, chlorophyll, carbon dioxide and water are necessary components to carry out the process of photosynthesis. And carbohydrates produced and ultimately converted into starch. During this process oxygen is released which is very essential for the survival all living organisms.

When a goat eats all the leaves of a small plant. Still new leaves could be seen sprouting in the plant again. This is just because the small plant survived on the food stored in the stem and roots. It might have undergone gaseous exchange through lenticels on stem.

We see slimy, green patches in ponds or in other stagnant water bodies. These are generally formed by the growth of organisms called “algae”. They contain chlorophyll. Algae can also prepare their own food by photosynthesis, so they are known as “Autotrophs”. We have also seen fluffy patches of white, green, brown color growing on rotting wood during the rainy season. These organisms are called “fungi”. They take in nutrients in solution form from dead and decaying matter, called “Saprotrophs”.