Question Answers For All Chapters – General Science Class 7
Nutrition in Living Organisms
Let’s recall.
1. What is malnutrition?
→ Malnutrition is a condition where the body does not get enough nutrients, vitamins, or minerals, leading to weakness, illness, and improper growth.
2. Which are the ways to prevent malnutrition?
Malnutrition can be prevented by:
- Eating a balanced diet rich in proteins, vitamins, and minerals.
- Drinking clean water to avoid infections.
- Taking nutritional supplements when necessary.
- Providing proper food to children and pregnant women.
- Raising awareness about healthy eating habits.
Find out
1. How does photosynthesis occur in dark red or purple-colored leaves?
→ Even though red or purple leaves appear different, they still contain chlorophyll, which is hidden by other pigments. Photosynthesis happens normally in these leaves.
2. What is chemosynthesis? Which plants produce their food by chemosynthesis?
→ Chemosynthesis is a process where plants or bacteria make food without sunlight, using chemical reactions. Bacteria found near ocean vents and deep soil use this method.
Let’s recall.
1. Which are the different substances excreted by plants? Why?
Plants excrete the following substances:
- Oxygen – Released during photosynthesis.
- Resins and gums – To heal wounds in trees.
- Latex (rubber) – To protect from insects.
- Excess water – Removed through transpiration.
Plants excrete these substances to remove waste and stay healthy.
Use your brain power !
1. Which part of the loranthus plant carries out photosynthesis?
→ The leaves of the loranthus plant carry out photosynthesis because they contain chlorophyll.
2. From where do they obtain minerals and water?
→ Loranthus is a partial parasite and absorbs water and minerals from the host tree through its special roots (haustoria).
3. Why is loranthus known as a partially parasitic plant?
→ Loranthus is called a partial parasite because it makes its own food through photosynthesis but takes water and minerals from the host plant.
4. Why does the pitcher plant feed on insects even though it produces food by photosynthesis ?
→ The pitcher plant produces food through photosynthesis, but it grows in nutrient-poor soil, especially lacking nitrogen. To get extra nutrients, it traps and digests insects, which provide nitrogen and proteins needed for its growth.
Exercise
1. Classify according to food type.
| Herbivores (Plant-eaters) | Carnivores (Meat-eaters) | Omnivores (Both plant & meat eaters) | Scavengers & Decomposers |
|---|---|---|---|
| Cow, Deer, Goat, Buffalo | Tiger, Lion, Frog | Human, Sparrow, Cockroach | Vulture, Bacteria, Fungus, Tick |
2. Match the pairs.
| Group ‘A’ | Group ‘B’ |
|---|---|
| (1) Parasitic plant | (d) Cuscuta |
| (2) Insectivorous plant | (c) Drosera |
| (3) Saprophytic plant | (a) Mushroom |
| (4) Symbiotic plant | (b) Lichen |
3. Answer the following questions in your own words.
(a) Why do living organisms need nutrition?
→ Nutrition provides energy for survival, growth, repair of tissues, and helps in fighting diseases.
(b) Explain the process of production of food in plants.
→ Plants use sunlight, carbon dioxide, and water to make food through photosynthesis with the help of chlorophyll.
(c) What is meant by parasitic plants? Name their different types with examples of each.
→ Parasitic plants depend on other plants for food.
- Complete parasite: Cuscuta (dodder plant) – depends fully on the host.
- Partial parasite: Loranthus – takes only water and minerals but makes its own food.
(d) Explain the various steps of nutrition in animals.
→ The five steps are:
- Ingestion (eating food)
- Digestion (breaking food into simpler forms)
- Absorption (nutrients enter the blood)
- Assimilation (nutrients are used by cells)
- Egestion (removal of waste)
(e) Name some unicellular organisms in which all life processes take place within their unicellular body.
→ Amoeba, Paramecium, Euglena, and Bacteria perform all life functions in a single cell.
4. Give reasons.
(a) Insectivorous plants are attractively colored.
→ Insectivorous plants grow in nutrient-poor soil, so they use bright colors to attract insects for food.
(b) Butterflies have a long tube-like proboscis.
→ Butterflies use their proboscis (long tube-like mouthpart) to suck nectar from flowers.
6. Think and Answer.
(a) We prepare a variety of foodstuffs and dishes at home. Are we then autotrophic organisms?
→ No, humans depend on plants and animals for food, so we are heterotrophic.
(b) Which organisms are greater in number – autotrophs or heterotrophs? Why?
→ Autotrophs (plants) are greater because they make food for themselves and other organisms in the food chain.
(c) The number of heterotrophs found in desert regions is smaller. However, they are found in greater numbers in the sea. Why?
→ Deserts have less food and water, so fewer animals survive. The sea has plenty of food sources, supporting more heterotrophs.
(d) What damage or harm do ectoparasitic and endoparasitic animals cause?
→ Ectoparasites (like lice, ticks) cause skin irritation and suck blood.
→ Endoparasites (like tapeworms) live inside the body and cause diseases.
(e) Why is plant food not produced in any other parts of the plant except the green ones?
→ Only green parts contain chlorophyll, which is necessary for photosynthesis to produce food.
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