4. Nutrition in Living Organisms

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Chapter 4 – Nutrition in Living Organisms (Class 7)

Chapter 4: Nutrition in Living Organisms

Class 7 • Maharashtra Board General Science Mobile-friendly • Neat & Colourful

1) 20 Important Words & Meanings (Meanings in Hindi)

Nutritionजीवों द्वारा भोजन लेने, पचाने, अवशोषित करने और उपयोग करने की प्रक्रिया।
Autotrophicजो स्वयं अपना भोजन बनाते हैं (जैसे हरे पौधे)।
Heterotrophicजो भोजन के लिए अन्य जीवों पर निर्भर रहते हैं।
Photosynthesisसूर्यप्रकाश व क्लोरोफिल की सहायता से $\\text{CO}_2$ और पानी से भोजन बनना।
Chlorophyllहरा वर्णक जो प्रकाश को सोखता है और भोजन बनाने में मदद करता है।
Stomataपत्तियों पर सूक्ष्म छिद्र जिनसे गैसों का आदान-प्रदान होता है।
Chloroplastपत्तियों की कोशिकाओं का अंगक जहाँ प्रकाश-संश्लेषण होता है।
Xylemजड़ से पानी व खनिज ऊपर पहुँचाने वाली नलिकाएँ।
Phloemपत्तियों में बने भोजन को अन्य भागों तक ले जाने वाली नलिकाएँ।
Symbiosisदो भिन्न जीवों का परस्पर लाभ के लिए साथ रहना।
Parasiteऐसा जीव/पौधा जो मेज़बान से भोजन लेकर जीता है।
Insectivorous plantऐसे पौधे जो कीड़ों को पकड़कर उनसे पोषण लेते हैं।
Saprophyteजो मृत/सड़ते पदार्थों से पोषण लेते हैं (कवक)।
Nitrogen fixationवायवीय नाइट्रोजन का यौगिकों (नाइट्रेट) में बदलना।
Rhizobiumदलहनी पौधों की गाँठों में पाया जाने वाला जीवाणु जो नाइट्रोजन स्थिरीकरण करता है।
Holozoic nutritionठोस भोजन लेकर पचाने वाला पोषण (अधिकांश जन्तु)।
Saprozoic nutritionद्रव जैव-पदार्थ को सोखकर पोषण लेना (कुछ कीट/सूक्ष्मजीव)।
Ectoparasiteजो शरीर की सतह पर रहकर भोजन चूसते हैं (जूं, खटमल)।
Endoparasiteजो शरीर के अंदर रहकर भोजन लेते हैं (टेपवर्म)।
Assimilationअवशोषित पोषक द्रव्यों का कोशिकाओं द्वारा उपयोग।

2) Important Notes (Quick Revision)

Balanced Photosynthesis: \(6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow[\text{chlorophyll}]{\text{sunlight}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2\)
  • Why nutrition? Energy for work; growth & development; tissue repair; disease resistance.
  • Macro vs Micro: Carbohydrates, proteins, fats (macro) • Vitamins & minerals (micro).
  • Autotrophs: Roots absorb water/minerals → xylem to leaves; leaves take \( \text{CO}_2 \) via stomata; chloroplasts convert light to glucose; phloem distributes food.
  • Not only leaves: Green stems can photosynthesize.
  • Purple/dark leaves: Chlorophyll present but masked by other pigments → photosynthesis continues.
  • Nitrogen for proteins: Plants use nitrates, not \( \text{N}_2 \). Sources: Rhizobium, Azotobacter, and lightning (→ \( \text{NO}, \text{NO}_2, \text{HNO}_3 \) → soil salts).
  • Symbiosis: Lichen (alga+fungus), mycorrhiza (fungus+roots).
  • Heterotrophic plants: Parasitic (Cuscuta — total; Loranthus — partial), Insectivorous (Drosera, pitcher), Saprophytic (mushroom, yeast).
  • Animal nutrition steps: Ingestion → Digestion → Absorption → Assimilation → Egestion.
  • Feeding modes: chewing, swallowing, sucking (proboscis), piercing-sucking, scraping, gnawing.
  • Food types: Herbivores, carnivores (incl. insectivores), omnivores, scavengers, decomposers.
  • Plant nutrients & deficiency: N (chlorophyll/proteins), P (energy transfer), K (metabolism), Mg (chlorophyll), Fe/Mn/Zn (enzymes & hormones). Deficiency → yellowing, stunting, weak stems, late flowering.

3) 20 Important “One-Word Answer” Type Questions

  1. Pigment that captures sunlight for photosynthesis?
    Chlorophyll.
  2. Microscopic leaf openings for gas exchange?
    Stomata.
  3. Organelle where photosynthesis occurs?
    Chloroplast.
  4. Tissue that transports water & minerals upward?
    Xylem.
  5. Tissue that distributes prepared food?
    Phloem.
  6. Primary product of photosynthesis?
    Glucose.
  7. Gas released during photosynthesis?
    Oxygen.
  8. Balanced chemical equation (symbolic)?
    \(6\text{CO}_2+6\text{H}_2\text{O}\to \text{C}_6\text{H}_{12}\text{O}_6+6\text{O}_2\).
  9. Bacteria fixing nitrogen in legume nodules?
    Rhizobium.
  10. Alga + fungus association is called?
    Lichen.
  11. Completely parasitic yellow wiry climber?
    Cuscuta.
  12. Partially parasitic plant on tree branches?
    Loranthus.
  13. Sticky-leaf insectivorous plant?
    Drosera.
  14. Feeding tube of butterflies?
    Proboscis.
  15. Temporary feet in Amoeba?
    Pseudopodia.
  16. First step in animal nutrition?
    Ingestion.
  17. Final step that expels undigested matter?
    Egestion.
  18. Animals that clean dead bodies?
    Scavengers.
  19. Organisms that decompose dead matter?
    Decomposers.
  20. Nutrition by absorbing dissolved organics?
    Saprozoic.

4) 20 Very Short Answer Questions (1–2 lines)

  1. Define nutrition.
    The process of taking in, digesting, absorbing, utilizing and egesting food.
  2. Why do plants need nitrogen?
    To build proteins & cytoplasm; they absorb it mainly as nitrates.
  3. How do purple leaves photosynthesize?
    Chlorophyll exists but is masked by other pigments; photosynthesis continues.
  4. Name the two plant transport tissues.
    Xylem and Phloem.
  5. What is symbiosis?
    Two species living together for mutual benefit (e.g., lichen).
  6. Why is Cuscuta a total parasite?
    It lacks chlorophyll and depends fully on its host for nutrition.
  7. Why is Loranthus a partial parasite?
    It photosynthesizes but takes water/minerals from host via haustoria.
  8. Why do insectivorous plants trap insects?
    To obtain nitrogen in nutrient-poor habitats.
  9. List the five steps of animal nutrition.
    Ingestion, digestion, absorption, assimilation, egestion.
  10. How does Amoeba ingest food?
    By surrounding it with pseudopodia; digestion occurs in food vacuoles.
  11. Give one saprophytic example.
    Mushroom / Yeast.
  12. Who fixes nitrogen in legume nodules?
    Rhizobium bacteria.
  13. Role of scavengers?
    They clean the environment and aid nutrient cycling.
  14. Two herbivores & two carnivores?
    Herbivores: cow, deer • Carnivores: lion, tiger.
  15. Mouthpart used by mosquitoes?
    Piercing-sucking proboscis.
  16. Energy change in photosynthesis?
    Light energy → chemical energy (food).
  17. Name two plant micronutrients.
    Iron, Zinc (also Manganese).
  18. What is chemosynthesis?
    Food production using chemical energy by bacteria.
  19. One symptom of N deficiency?
    Yellowing (chlorosis) and stunted growth.
  20. Which step uses absorbed food?
    Assimilation.

5) 20 Short Answer Questions (2–3 lines)

  1. Differentiate autotrophic and heterotrophic nutrition.
    Autotrophs (plants) make food via photosynthesis; heterotrophs obtain food from plants/animals.
  2. How do water and minerals reach leaves?
    Roots absorb them; xylem conducts upwards through the stem to leaves.
  3. What happens to oxygen formed in photosynthesis?
    It diffuses out via stomata and may dissolve in surrounding water/air.
  4. How is food distributed in plants?
    Phloem translocates sugars (often as sucrose) to growing and storage tissues.
  5. Describe atmospheric nitrogen fixation.
    Lightning forms \( \text{NO}, \text{NO}_2 \); dissolving yields \( \text{HNO}_3 \), which forms soil nitrates usable by plants.
  6. Explain symbiotic nutrition with two examples.
    Lichen (alga+fungus) and mycorrhiza (fungus+roots) exchange nutrients for mutual benefit.
  7. Why is Drosera colourful and sticky?
    Colour attracts insects; sticky mucilage traps them to provide nitrogen.
  8. Why is Cuscuta leafless?
    It is a total parasite without chlorophyll; leaves are absent/reduced.
  9. How do fungi obtain food from dead matter?
    They secrete enzymes externally to digest, then absorb simpler molecules.
  10. Summarize animal nutrition steps.
    Ingestion → Digestion → Absorption → Assimilation → Egestion; each essential for using food.
  11. How does Amoeba perform all steps in one cell?
    Food vacuoles handle digestion/absorption; wastes exit through the cell surface.
  12. Classify animals by diet with examples.
    Herbivores (cow), carnivores (lion), omnivores (human), scavengers (vulture), decomposers (bacteria).
  13. Define ecto- vs endoparasites with examples.
    Ectoparasites live on body surface (louse, tick); endoparasites live inside (tapeworm, roundworm).
  14. Why are scavengers & decomposers vital?
    They recycle nutrients and prevent accumulation of dead matter.
  15. Name macronutrients and why needed.
    Carbohydrates, proteins, fats — required in large amounts for energy, growth, repair.
  16. Two nutrient deficiencies and symptoms.
    N: chlorosis & stunting; Mg: poor chlorophyll, interveinal yellowing.
  17. What is chemosynthesis? Name an organism.
    Synthesis using chemical energy; e.g., nitrifying bacteria like Nitrosomonas.
  18. Why no separate digestive system in plants?
    They produce simple food (glucose) directly; no complex solid digestion required.
  19. Why do mouthparts vary among animals?
    Adaptations to diet/feeding (chewing, sucking, piercing, gnawing) increase efficiency.
  20. Role of phloem in storage organs.
    It delivers sugars to roots/fruits/tubers where they’re converted & stored (e.g., starch).

6) Textbook Exercise – Perfect Answers

Q1) Classify according to food-type: tiger, cow, vulture, bacteria, deer, goat, human, fungus, lion, sparrow, buffalo, frog, cockroach, tick.
CategoryExamples
Herbivorescow, deer, goat, buffalo
Carnivorestiger, lion, frog (insectivore)
Omnivoreshuman, sparrow (grains & insects), cockroach (omnivorous scavenger)
Scavengersvulture
Decomposers (Saprophytes)bacteria, fungus
Ectoparasitetick
Q2) Match the pairs.
Group ACorrect match (Group B)
(1) Parasitic plant(d) Cuscuta
(2) Insectivorous plant(c) Drosera
(3) Saprophytic plant(a) Mushroom
(4) Symbiotic plant(b) Lichen
Q3) Answer the following questions in your own words.
  1. (a) Why do living organisms need nutrition?
    For energy, growth & development, tissue repair and immunity; nutrition fuels all life processes.
  2. (b) Explain the process of production of food in plants.
    Leaves use sunlight & chlorophyll to convert \( \text{CO}_2 \) and water (via xylem) into glucose and oxygen: \(6\text{CO}_2+6\text{H}_2\text{O}\to\text{C}_6\text{H}_{12}\text{O}_6+6\text{O}_2\). Food then moves by phloem.
  3. (c) What are parasitic plants? Types with examples.
    Plants deriving nutrition from hosts via haustoria. Complete parasite: Cuscuta. Partial parasite: Loranthus (photosynthesizes but taps host water/minerals).
  4. (d) Explain the various steps of nutrition in animals.
    Ingestion → digestion (enzymatic breakdown) → absorption (into blood) → assimilation (use by cells) → egestion (undigested waste out).
  5. (e) Name some unicellular organisms with all life processes within one cell.
    Amoeba, Euglena, Paramecium.
Q4) Give reasons.
  1. (a) Insectivorous plants are attractively coloured.
    To lure insects towards traps so the plants can obtain nitrogen.
  2. (b) Butterflies have a long tube-like proboscis.
    It is adapted to suck nectar from deep flowers — perfect for a liquid diet.
Q5) Prepare and complete the flowchart according to type of nutrition.
Nutrition→ Plants (Autotrophic • Insectivorous • Parasitic [Partial/Complete])   |   Animals (Holozoic • Saprozoic • Parasitic [Ecto/Endo])
Q6) Think and answer.
  1. (a) We prepare many dishes at home. Are we autotrophs?
    No. We don’t synthesize food from inorganic raw materials using light; we are heterotrophs who process existing food.
  2. (b) Which are more numerous—autotrophs or heterotrophs? Why?
    Heterotrophs are more diverse and numerous (animals, fungi, many microbes) and depend on autotrophs for energy.
  3. (c) Why fewer heterotrophs in deserts but many in seas?
    Deserts have low water & primary productivity; seas have abundant water and phytoplankton, supporting vast food webs.
  4. (d) What damage do ecto- and endoparasites cause?
    Ectoparasites cause skin irritation & transmit disease; endoparasites cause malnutrition, anemia and internal damage.
  5. (e) Why is plant food produced only in green parts?
    Because chlorophyll (green pigment) is essential for photosynthesis; non-green parts lack enough chlorophyll.

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