CDS (II) 2021 General Knowledge · Question 18 of 120

Correct — A, Yeast, mushroom, bread mould. Breaking food down outside the body and then absorbing the products is saprophytic nutrition, and it is what fungi do. A bread mould growing on a slice of bread secretes digestive enzymes onto the substrate, the enzymes dissolve the starch and protein where they lie, and the fungus takes up the soluble products through its hyphae; yeast and mushrooms feed the same way. The textbook sentence behind this item names exactly that trio — some organisms break down the food material outside the body and then absorb it, examples being fungi like bread moulds, yeast and mushrooms. The three wrong options are built from the two other feeding strategies in the same passage. Parasites such as ticks, lice and tapeworms draw nutrition from a living host without killing it, and single-celled feeders such as Amoeba and Paramecium engulf whole particles and digest them internally, in food vacuoles. Green plants make their own food and do not take any in at all.

• (b)Mushroom, Amoeba, green plants — Only the mushroom fits. Amoeba engulfs its food and digests it inside a food vacuole, and a green plant manufactures its own food by photosynthesis rather than absorbing digested material.
• (c)Caserta, tapeworm, lice — This is the parasite list, not the saprophyte list. All three draw nourishment from a living host; none secretes enzymes onto dead organic matter and absorbs the products.
• (d)Paramecium, Amoeba, Caserta — Mixes two other strategies. Paramecium and Amoeba take in whole material and break it down internally, while the third is a parasite of living plants.

Heterotrophs obtain ready-made food, and they do it in three broad ways. Saprophytes secrete enzymes onto dead organic matter, digest it outside the body and absorb the soluble products — the fungal method. Parasites take nutrition from a living host without killing it. Holozoic feeders ingest whole material and digest it inside the body, whether in a food vacuole as in Amoeba or in an alimentary canal as in animals. Autotrophs, chiefly green plants, sit outside this scheme entirely because they synthesise their own food.

Each wrong option is a working list of some other feeding type, so the question rewards sorting organisms by strategy rather than by looks. Fungi are the group to lock down: a mould, a mushroom and a yeast are all fungi, all lack chlorophyll, and all feed by external digestion. One point of vocabulary belongs on this card. The paper prints 'Caserta' in options (c) and (d) where the textbook sentence the item is drawn from reads 'cuscuta' — the parasitic dodder, known in India as amar-bel, a leafless twining plant that draws its food from a host through specialised roots. That printed slip is reproduced here exactly as it appeared in the booklet, and it does not change what is being tested: cuscuta belongs with tapeworms and lice as a parasite, which keeps options (c) and (d) wrong either way.

• Some organisms break down food material outside the body and then absorb it; the textbook examples are fungi such as bread moulds, yeast and mushrooms.
• The parasitic strategy of drawing nutrition from a living host without killing it is used by cuscuta (amar-bel), ticks, lice, leeches and tapeworms.
• Amoeba and Paramecium are holozoic single-celled feeders: they take in whole material and digest it internally in food vacuoles.
• Green plants are autotrophs and manufacture their own food by photosynthesis, so they do not take food in at all.
• Fungi lack chlorophyll and absorb nutrients through the fine threads of the mycelium, called hyphae.

• Putting green plants into a list about taking in food; autotrophs make their own.
• Treating all microbes as one feeding type — Amoeba engulfs, while yeast absorbs.
• Mistaking the parasitic list for the saprophytic one; parasites feed on a living host, saprophytes on dead matter.

As a group-the-organisms item like this one, as a mode-of-nutrition match, or as a question on a single named organism such as Rhizopus, Cuscuta or Amoeba.

• practice — not a real PYQ

  Cuscuta, commonly called amar-bel, obtains its nutrition by

  • (a)photosynthesis
  • (b)drawing food from a living host plant
  • (c)secreting enzymes onto dead matter and absorbing the products
  • (d)engulfing food particles

  Answer(b) drawing food from a living host plant — it is a parasite, not a saprophyte, and lacks chlorophyll of its own.

• practice — not a real PYQ

  Which one of the following organisms digests its food inside a food vacuole?

  • (a)Yeast
  • (b)Bread mould
  • (c)Amoeba
  • (d)Mushroom

  Answer(c) Amoeba — it engulfs the food particle with pseudopodia and digests it internally, unlike the three fungi listed.