Nutrition Process by which organisms obtain and use the nutrients required for maintaining life

Modes of nutrition Ways of obtaining and using nutrients Nutrition Autotrophic nutrition Heterotrophic nutrition Holozoic nutrition Saprophytic nutrition Parasitic nutrition

Autotrophic nutrition make their own food (complex organic substances) using simple inorganic substances –the organism  autotrophs e.g. Green plants –by photosynthesisby photosynthesis

Heterotrophic nutrition depends on other organisms or dead organic matters as their food sources –the organism  Heterotrophs Cannot make their own food Obtain their food in organic form

Holozoic nutrition Organisms take in solid organic food from ingesting other living organisms Food needs to be broken down into small molecules (i.e. digested) before they can be absorbed and used by the organisms

Types of animals taking holozoic nutrition Herbivores –Feed on plants only Carnivores –Feed on animals only Omnivores –Feed on both plants and animals

Saprophytic nutrition (Saprophytism) Organisms feed on dead organisms or non- living organic matter –Saprophytes (e.g. fungi, bacteria)

How a saprophyte obtains its nutrients? Example : Mucor & Rhizopus (bread mould) Hyphae release digestive enzyme into the bread Enzymes digest complex organic molecules in bread into simple, soluble molecules (extracellular digestion ) Digested products are absorbed by hyphae Mass of hyphae = mycelium Sporangium : produces spores for reproduction bread hyphae sporangium enzyme secreted

Importance of saprophytes As decomposers –Allow essential materials (e.g. C, N) to be recycled in the ecosystem Complex organic substances Simple soluble compounds Enzyme from saprophytes

To observe Mucor

Why is it necessary to leave the moist bread uncovered for 30 minutes ? Ans: Because the spores of Mucor are carried by air current. They can drop onto the bread and then germinate.

What are the thread-like structures growing on the surface of the bread ? Ans: Hyphae. Hyphae are used for feeding. Hyphae can produce enzymes for digesting the organic food.

Parasitic nutrition (Parasitism) Organisms (parasite) obtain organic compounds from another living organism of a different species (host) –Parasite is benefited –Host is harmed

How a tapeworm obtains its nutrient? Food in small intestine is already digested  Can be absorbed directly through the body wall of tapeworm by diffusion Food absorbed directly from the ileum Toxic wastes released into the ileum Lives inside the small intestine of human

Structural adaptations of tapeworm Head bears hooks and suckers –To attach itself to the intestinal wall of the host  Prevent being egested by peristalsis of intestine

Structural adaptations of tapeworm Long, flattened body –To increase the surface area for more absorption of digested food by diffusion Body covered by cuticle & secretes anti- enzyme –To protect itself from the attack of digestive enzymes from the host

Parasitic nutrition (Parasitism) Lose weight & become weaker Parasite produces toxic compounds  harm the host May block the ileum Difficult movement of food along the intestine Hooks & suckers damage host’s intestinal wall Effects on Host:

To observe a Tapeworm

Does the tapeworm have a mouth ? Ans: No, tapeworm does not have a mouth.

Does the tapeworm have a digestive tract ? Why ? Ans: No. It is not necessary for a tapeworm to digest food because it obtains food directly from its host’s ileum by diffusion.

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