Science textbook solutions for Class 7 Science Chapter 4 Nutrition in Living Organisms - YB Study

Science textbook solutions for Class 7 Science Chapter 4 Nutrition in Living Organisms

Nutrition in Living Organisms Textbook Solutions:


Nutrition in Living Organisms Textbook Solutions

Important points to remember :
  1. The process of taking in and using food, which takes place in living organisms is called nutrition. 
  2. Autotrophic nutrition Some organisms can produce their own food and thus nourish themselves. This is called autotrophic nutrition. 
  3. Heterotrophic nutrition Some organisms depend on other organisms, plants or animals, for their food. This is called heterotrophic nutrition. 
  4. Nutrients can be classified into two types, namely, macro-nutrients and micronutrients. 
  5. The transport system of plants consists of the xylem and the phloem. 
  6. two or more two different types of plants live together to fulfill their needs of nutrition, protection, support, etc. with each others’ help. This type of nutrition is called symbiotic nutrition. 
  7. Food gets spoiled due to some fungi. Some fungi cause diseases or illnesses while some fungi have medicinal properties. 
  8. Yeast and some mushrooms are useful. Yeast is used in fermentation processes and for making bread. Mushrooms are a rich source of iron and vitamins. 


Class 7 Science Chapter 4 Nutrition in Living Organisms Textbook Solutions:

Question 1: Classify according to food type.
tiger, cow, vulture, bacteria, deer, goat, human, fungus, lion, sparrow, buffalo, frog, cockroach, tick.
Answer :
tiger- carnivore
cow- herbivore
vulture- scavenger
bacteria- decomposers
deer- herbivore
goat- herbivore
human- omnivore
fungus- decomposers
lion- carnivores
sparrow- herbivore
buffalo- herbivore
frog- carnivore
cockroach- carnivore
tick- parasite


Question 2: Match the pairs.
Group 'A'.                             Group 'B'
1) Parasitic plant.               a) Mushroom

2) Insectivorous plant.      b) Lichen

3) Saprophytic plant.        c) Drosera

4) Symbiotic plant.            d) Cuscuta

Answer : 
1) Parasitic plant - d) Cuscuta
2) Insectivorous plant - c) Drosera
3) Saprophytic plant - a) Mushroom
4) Symbiotic plant -b) Lichen


Question 3: Answer the following questions in your own words.
a) Why do living organisms need nutrition?
Answer: because most of the life processes like metabolism, respiration, and excretion go on continuously in living organisms. Substances are digested and assimilated for obtaining energy and for growth and health that's why nutrients are required.
Need for nutrition 
1. To supply the energy required for doing work.
2. Growth and development of the body.
3. To replace the damaged cells and repair tissues.
4. To fight diseases.

b) Explain the process of production of food in plants.
Answer: Plants also need food for their growth.
  1. They can produce their own food.  With the help of sunlight and chlorophyll, plants make their food in their leaves, using water and nutrients from the soil and carbon dioxide from the air. This process is called photosynthesis. 
  2. Plants convert light energy into chemical energy and store it in the form of food. Water, minerals, and salts are absorbed by roots from the soil. 
  3. The stem transports them up to the leaves. The leaves have microscopic openings called stomata through which they take in the CO2  from the air. 
  4. The chloroplasts present in the leaves contain chlorophyll, which absorbs sunlight,  helping to convert carbon dioxide and water into food. 
  5. Oxygen is given out in this process. Besides leaves,  photosynthesis takes place in some other parts like green stems, too, as they contain chlorophyll.

c) What is meant by parasitic plants? Name their different types with examples of each.
Answer: Cuscuta is known as a parasite as it depends on another plant for its survival. The plant on which it grows is known as the host. Cuscuta can be seen around in the form of yellow tubular structures growing on the stems of other plants. It is devoid of leaves. Another example of a parasitic plant is Loranthus.

d) Explain the various steps of nutrition in animals.
Answer: Steps in nutrition
1.  Ingestion  - Food is taken into the body. 2.  Digestion  - Conversion of food into simple soluble forms.
3.  Absorption  - Transfer of soluble food to the blood.
4.  Assimilation  - Utilization of absorbed food by cells and tissues for energy production, growth, and repair.
5.  Egestion  - Removal of waste products and undigested food from the body.

e) Name some unicellular organisms in which all life processes take place within their unicellular body.
Answer: Many prokaryotic or unicellular organisms in which all life processes take place within their body are- Amoeba, Paramoecium, BGA, and Euglena.


Question 4: Give reasons.
a) Insectivorous plants are attractively colored.
Answer: Many Insectivorous plants are attractively colored so that they can attract insects and feed upon them. Insectivorous plants grow in soil or water which are deficient in nitrogen compounds and to meet this deficiency, they feed on insects.

b) Butterflies have a long tube-like proboscis.
Answer: Butterflies have a long tube-like proboscis which is a straw-like structure that enables them to drink juices and nectar. It is coiled up like a garden hose when it is not in use.


Question 6: Think and answer.
a) We prepare a variety of foodstuffs and dishes at home. Are we then autotrophic organisms?
Answer: We prepare a variety of foodstuffs and dishes at home. This does not make us autotrophs. This is because autotrophs prepare food on their own with the help of sunlight, water, minerals, and chlorophyll.

b) Which organisms are a more significant number - autotrophs or heterotrophs? Why?
Answer: Heterotrophs are greater in number as autotrophs are the only organisms with chlorophyll that helps them produce their food. Autotrophs are less in number. Such types of organisms are larger in number. Hence Heterotrophs are greater in number.

c) The number of heterotrophs found in desert regions is smaller. However, they are found in greater numbers in the sea. Why is this so?
Answer: The number of heterotrophs found in desert regions is smaller. This is because in desert regions the number of autotrophs is less and this provides less number of sources of food to the heterotrophs which, in turn, affects the food chain.

d) What damage or harm do ectoparasitic and endoparasitic animals cause?
Answer: Ectoparasites and endoparasites are devoid of the host of their nutrition. Some of the parasites are known to cause diseases like Ascaris/roundworm which is an endoparasite of the intestine and causes ascariasis. Another example is Wuchereria which causes elephantiasis or filariasis. It is an endoparasite that lives in lymphatic vessels of lower limbs.


e) Why is plant food not produced in any other parts of the plant except the green ones?
Answer: Plant food is only produced in the green part of the plants as chlorophyll is present in those green parts. The broad hard part of the plants does not possess any chlorophyll and therefore plant food cannot be created in those parts.


# let's recall 
1. What is malnutrition? 
Answer: Malnutrition means a lack of proper nutrition, caused by not having enough to eat, not eating enough of the right things, or being unable to use the food that one does eat.

2. What are the ways to prevent malnutrition?
Answer: The best way to prevent malnutrition is to eat a healthy, balanced diet.

Preventing malnutrition
  1. plenty of fruit and vegetables. 
  2. plenty of starchy foods such as bread, rice, potatoes, and pasta. 
  3. some milk and dairy foods or non-dairy alternatives. 
  4. some sources of protein, such as meat, fish, eggs, and beans.


3. Which are the different substances excreted by plants? Why?.
Answer: The different substances excreted by plants are oxygen, carbon dioxide, and water droplets. Explanation: Plants release oxygen during the day. This oxygen is a by-product of photosynthesis

4. What are the various nutrients in food?  For what purpose are the nutrients used? 
Answer: Nutrients necessary for various activities of the body are obtained from food. They are supplied to the various parts of the body through blood. The food that we consume does not mix with blood as it is. It needs to convert into soluble forms that can easily mix in the blood. Nutrition in animals involves various steps from ingestion to egestion.

# Find out
1. How does photosynthesis occur in dark red or purple-colored leaves ? Answer: In photosynthesis, plants convert light energy to chemical energy. Typically, chlorophyll absorbs mostly red and blue light to excite the electrons in the photosystems for photosynthesis. Hence, plants with higher concentrations of carotenoids will appear dark red or purple.

2. What is chemosynthesis? Which plants produce their food by chemosynthesis?
Answer:  Chemosynthesis is the conversion of one or more carbon-containing molecules and nutrients into organic matter using the oxidative inorganic compounds or methane as an energy source as in photosynthesis.


# Use your brain power
1. Which part of the Loranthus plant carries out photosynthesis?
Answer - Leaves of the Loranthus plant carry out photosynthesis.

2. From where do they obtain minerals and water? 
Answer: soil

3. Why is Loranthus known as a  partially parasitic plant?
Answer: Loranthus plants are famous partially parasitic plants as they can absorb nutrients as well as water from other plants, they do not grow on soil instead they have a special system known as "Historia" by which it penetrates into the woody tree and grows on aerial parts of the tree.


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