CBSE Questions for Class 7 Biology Nutrition In Plants Quiz 2 - MCQExams.com

• Rhizobium is soil bacteria, that fix nitrogen after becoming established inside root nodules of legumes (Fabaceae). 
• To fix nitrogen, Rhizobium requires a plant host; they cannot independently fix nitrogen. In general, they are Gram-negative, motile, non-sporulating rods. 
• In presence of nitrogen, they can fix nitrogen. So, supplying nitrogen to them can be helpful for nitrogen fixation.

• Green plants are autotrophic organisms because they can synthesize their own food by photosynthesis. 
• During photosynthesis energy from sunlight is converted into chemical energy in the form of organic compounds and oxygen is released as a by-product.
•  Animals, fungi and several bacteria are heterotrophic organisms and depend on organic compounds synthesized by autotrophs for their nutrition.
• So, the correct answer is 'Autotrophs'

• Organisms that cannot synthesize their own food are called heterotrophs. Heterotrophs depend directly or indirectly on autotrophs for their food.
• Autotrophs are the organism that can produce their own food using light, water, carbon dioxide, or other chemicals.
• Algae are autotrophs.

• Certain plants provide shelter to nitrogen-fixing bacteria in small swollen structures present on the roots called root nodules. 
• The nitrogen-fixing bacteria, colonize the roots of the plants. This initiates the formation of nodules on the roots. 
• The bacteria then use those nodules as their shelter. Plants cannot use atmospheric nitrogen directly. 
• Therefore, nitrogen-fixing bacteria present in root nodules fix nitrogen or convert the atmospheric nitrogen into usable forms that can be taken up by the plants. 

• According to their food requirements, living organisms can be producers that produce their own food by photosynthesis or consumers, which depend on producers for their food. 
• Among consumers, organisms that eat plant and their products are called herbivores, and the ones that eat other animals are carnivores.
• In the given question, the first, third, and fourth images are of a cat, eagle, and snake. All of them are carnivores. While the second image is that of a monkey, which is a herbivore.

• Autotrophs absorb water and minerals from the soil and use the light energy of the sun to synthesize sugars (chemical energy).  
• Photosynthesis is a redox reaction in which water is oxidized and carbon dioxide is reduced.

• Dodder (Cuscuta) is a parasitic plant. It lacks chlorophyll hence it appears as yellow tubular structures.
• They develop haustoria or sucking roots which go into the vascular bundles of the host plant and absorb from them the prepared food and water.

$$\textbf{Correct answer: D}$$ 

$$\textbf{Option (A):}$$ 

$$\bullet$$ The birds mainly feed on the sprouted seeds. Other herbivores may feed on such sprouting seeds.

$$\textbf{Option (B):}$$ 

$$\bullet$$ The food source of carnivorous animals is not milk. 

$$\textbf{Option (C):}$$ 

$$\bullet$$ The herbivores feed on green leaves and they are present as primary consumers. 

$$\bullet$$ These organisms feed on the producers, which are the green plants. 

$$\textbf{Option (D):}$$ 

$$\bullet$$ Carnivores feed on the flesh of other animals as they are present as secondary consumers in the ecosystem. 

$$\bullet$$ They feed on the flesh as they can draw their energy and nutrition from that source directly. 

Hence, the correct answer is option (D).

• A parasite is an organism that lives on or in a host organism and gets its food or nutrition from its host (plants and animals). There are three main classes of parasites that can cause disease in humans: protozoa, helminths and ectoparasites.
• Parasites come in many shapes and sizes and include viruses and bacteria, various worms, plants, fungi, insects, and even birds and mammals.
  

• Green plants are capable of producing their own food by the process of photosynthesis. They prepare food using carbon dioxide, water, sunlight, and chlorophyll. Thus, they are called primary producers or autotrophs. 
• Heterotrophs are organisms that are incapable of making their own food from light or inorganic compounds. They feed on other organisms or the remains of other organisms.

• Autotrophs are organisms that can produce their own food using light energy through photosynthesis or by using chemical energy through the process of chemosynthesis. 
• Heterotrophs cannot synthesize their own food and are dependent on autotrophs for nutrition. 

• A plant requires nutrients for its growth and development. 
• The nutrients are absorbed through the soil. The nutrient-supplying sources are manures and fertilizers. 
• The application of manures and fertilizers to the soil is one of the important factors that help in increasing crop yield and maintaining soil fertility. 
• Nitrogen, phosphorous, and potassium are the three major elements required for crop growth. 

• The green plants, algae, and other organisms which possess the chlorophyll pigment are known as producers. 
• They are autotrophs that can utilize the energy from the sun and prepare their own food. 
• They are the only producers which can synthesize the food products.