Heterotrophic Nutrition and Digestion – Long Answer Questions
Medium Level (Application & Explanation)
Q1. Explain the different types of heterotrophic nutrition with suitable examples.
Answer:
- Heterotrophic nutrition means organisms get food from other sources.
- In saprophytic nutrition, organisms absorb nutrients from dead matter.
- Example: Fungi like bread moulds and mushrooms secrete enzymes and absorb the digested food.
- In parasitic nutrition, organisms live on a host and draw nourishment without killing it.
- Example: Cuscuta (plant parasite) and certain leeches.
- In holozoic nutrition, organisms ingest food and digest it internally.
- Example: Carnivores like lions eat other animals and digest food inside the body.
Q2. Describe how Amoeba and Paramecium obtain their food. Compare their methods.
Answer:
- Amoeba uses pseudopodia (false feet) to surround food.
- It forms a food vacuole, where enzymes digest the food.
- The digested food is absorbed, and waste is thrown out.
- Paramecium uses many cilia to push food into an oral groove.
- Food enters a vacuole and is digested in a similar way.
- Amoeba follows phagocytosis by engulfing any nearby particle.
- Paramecium has a fixed pathway for food intake using its specialized oral groove.
Q3. Explain the structure of the human alimentary canal and the function of its main parts.
Answer:
- The mouth has teeth for chewing and saliva to start starch digestion.
- The food passes through the esophagus into the stomach.
- The stomach secretes acid and enzymes for protein digestion.
- The small intestine is the main site for digestion and absorption.
- Secretions from the liver and pancreas help in breaking down food.
- The large intestine absorbs water and forms feces.
- The rectum stores waste, and the anus helps in excretion.
Q4. How does saliva help in digestion? Explain using the starch–iodine activity.
Answer:
- Saliva contains salivary amylase, an enzyme that breaks down starch.
- In the activity, starch solution is kept in two test tubes, A and B.
- Saliva is added to A, while B is left as a control.
- After some time, iodine is added to both tubes.
- Tube B turns blue-black, showing starch is still present.
- Tube A does not turn blue-black, showing starch was digested.
- This proves saliva starts digestion in the mouth.
Q5. Why do herbivores have longer intestines than carnivores? Explain with reasons.
Answer:
- Herbivores eat plants that are rich in cellulose.
- Cellulose is hard to digest and needs more time.
- A longer intestine gives more surface area and time for digestion.
- This helps in better absorption of nutrients from plant food.
- Carnivores eat meat, which is easier to digest.
- So, carnivores usually have shorter intestines.
- This difference matches their diet and digestive needs.
High Complexity (Analysis & Scenario-Based)
Q6. Suppose a person has very low salivary amylase. Predict what happens during starch digestion and in the iodine test.
Answer:
- With low salivary amylase, starch will not break down well in the mouth.
- The person may feel food is heavy and digestion is slower at the start.
- In the iodine test, the tube with saliva may still turn blue-black.
- This means starch remains and is not broken into simple sugars.
- Later parts like the small intestine will try to digest the starch.
- But the initial mechanical and chemical advantage is lost.
- The person may feel discomfort after starch-rich meals.
Q7. A student neglects brushing and eats many sugary snacks. Explain how plaque leads to dental caries and how to prevent it.
Answer:
- Food and bacteria form a sticky layer called plaque on teeth.
- Bacteria act on sugars and produce acids.
- These acids damage the enamel and cause tooth decay.
- Plaque also blocks saliva from neutralizing acids.
- Prevention: Brush regularly to remove plaque.
- Limit sugary foods to reduce acid production.
- Good oral hygiene keeps teeth safe from caries.
Q8. Compare external digestion in fungi with internal digestion in carnivores. What does this show about adaptation?
Answer:
- Fungi perform external digestion. They secrete enzymes on dead matter.
- They then absorb the simpler nutrients into their body.
- Carnivores perform internal digestion inside an alimentary canal.
- They ingest food first, then digest it with enzymes in the stomach and intestines.
- This shows organisms adapt to their environment and food source.
- Fungi suit decomposing habitats; carnivores suit hunting lifestyles.
- Different structures support different nutrition strategies.
Q9. Design an experiment to test the effect of temperature on salivary amylase using the starch–iodine method. State controls and expected results.
Answer:
- Take three sets of tubes with starch solution. Label as Cold, Room, and Warm.
- Add equal amounts of saliva to each set.
- Keep them at low, room, and warm temperatures for 20–30 minutes.
- Add iodine to each tube after the wait.
- Control: a tube with starch only (no saliva) must turn blue-black.
- Expected: Room/Warm work better, showing little to no blue-black color.
- Cold slows the enzyme; it likely stays blue-black, showing less digestion.
Q10. Track what happens to a bite of bread from mouth to anus. Explain the major changes and roles of organs.
Answer:
- In the mouth, teeth chew and saliva starts starch digestion.
- The bolus moves through the esophagus to the stomach.
- The stomach uses acid and enzymes to act mainly on proteins.
- In the small intestine, enzymes from liver (bile aids) and pancreas help digestion.
- Villi in the small intestine absorb nutrients into the blood.
- The large intestine absorbs water and forms feces.
- Waste is stored in the rectum and leaves through the anus.