Chapter 4 Nutrition in Living Organisms Std 7 Class 7

General Science Lesson 4 Nutrition in Living Organisms


Classify according to food-type.

tiger, cow, vulture, bacteria, deer, goat, human, fungus, lion, sparrow, buffalo, frog, cockroach, tick.

Tiger carnivore
Cow herbivore
Vulture scavenger
Bacteria decomposer
Deer herbivore
Goat herbivore
Human omnivore
fungus decomposer
Lion carnivore
Sparrow omnivore
Buffalo herbivore
Frog carnivore
Cockroach carnivore
tick parasite

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

Ans. 1 – d,   2 – c,   3 – a,  4 – b    

3. Answer the following questions in your own words.

(a) Why do living organisms need nutrition?

Ans. Living Organisms feed 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.

Ans. Plants produce their own food through the process of photosynthesis. 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. 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. The chloroplasts present in the leaves contain chlorophyll, which absorbs sunlight, helping to convert carbon dioxide and water into food. Oxygen is given out in this process.

(c) What is meant by parasitic plants? Name their different types with examples of each.

Ans. Carbon dioxide + water        Sunlight         food (glucose) + oxygen

6 CO2               + 6H2 O     Chlorophyll            C6 H12 O6      + 6O2

(d) Explain the various steps of nutrition in animals.

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 body  

(e) Name some unicellular organisms in which all life-processes take place within their unicellular body.

Ans. In unicellular animals like amoeba, euglena, paramoecium, etc. all the steps of nutrition occur within their unicellular body.

4. Give reasons.

(a) Insectivorous plants are attractively coloured.

Ans. Insectivorous plants generally grow in soil or water deficient in nitrogen compounds, in order to meet their need for nitrogen these plants feed on insects and to attract the insects they are attractively coloured.

(b) Butterflies have a long tube-like proboscis.

Ans. The butterflies feed on nectar from the flowers and in order to suck the nectar from the flowers they have long tube-like proboscis.

5. Prepare and complete the flowchart according to type of nutrition.

6. Think and answer.

(a) We prepare a variety of foodstuffs and dishes at home. Are we then autotrophic organisms?

Ans. Organisms that can prepare their own food are called autotrophs. Though we prepare our own food, we get them through plants. There we cannot be called autotrophic organisms.

(b) Which organisms are greater in number – autotrophs or heterotrophs ? Why?

Ans. Aurotrophs are greater in number. Heterotrophs depend on autotrophs for their food. If heterotrophs were greater in number then they would consume all the autotrophs and autotrophs would parish. Later even hetrptrophs would become extinct.

(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?

Ans. The climate in the desert is extremely hot so we find autotrophs in very small number. And as heterotrophs depend on autotrophs for food, we find hetertrophs are also found in small number in desert regions. However in the sea there are plenty of autotrophs and so the number of heterptrophs is also large.

(d) What damage or harm do ectoparasitic and endoparasitic animals cause?

Ans. Some animals depend upon other animals for food. They can obtain the food only from animals on which they are dependent. These animals are called as parasitic animals. The ectoparasitic animals live on the bodies of other animals e.g. lice and ticks. They suck the blood of the host animal. The endoparasitic animals live inside the bodies of other animals and obtain their food e.g. tapeworms and roundworms. These parasitic animals depend on the host animal for their food and so the host animal is devoid of nutrients.

(e) Why is plant food not produced in any other parts of the plant except the green ones?

Ans. The chloroplasts present in the leaves contain chlorophyll, which absorbs sunlight, helping to convert carbon dioxide and water into food. Since chlorophyll is green in colour, the green parts of a plant indicate the presence of chlorophyll. Thus plant food is produced only in the green parts of a plant.

Project :

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1. Many heterotrophic organisms live on one and the same plant. Observe one such plant in your neighbourhood and find out about the heterotrophs that depend upon it for their food. Observe and make notes about other organisms that use these heterotrophs as their food.

2. Prepare a power point presentation on the topic ‘Nutrition in Living Organisms’.

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