NutritionNutrition

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

Modes of nutritionModes of nutrition• Ways of obtaining and using nutrients

Nutrition

Autotrophic nutrition

Heterotrophic nutrition

Holozoic nutrition

Saprophytic nutrition

Parasitic

nutrition

Autotrophic nutritionAutotrophic nutrition• make their own food (com

plex organic substances) using simple inorganic substances– the organism autotrophs

• e.g. Green plants– by photosynthesis

Heterotrophic nutritionHeterotrophic nutrition• depends on other organisms or dead

organic matters as their food sources– the organism Heterotrophs

• Cannot make their own food and obtain their food in organic form

Holozoic nutritionHolozoic 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 absorbedand used by the organisms

Types of animals Types of animals taking holozoic ntaking holozoic n

utritionutrition• Herbivores

– Feed on plants only

• Carnivores– Feed on animals only

• Omnivores– Feed on both

plants and animals

Saprophytic nutritionSaprophytic nutrition(Saprophytism)(Saprophytism)

• Organisms feed on dead organisms or non-living organic matter– Saprophytes

(e.g. fungi, bacteria)

How a saprophyte How a saprophyte obtains its obtains its nutrients?nutrients?

Example : Mucor & Rhizopus (bread mould)

• Hyphae release digestive enzyme into the bread

• Enzymes digest complex organic molecules in bread into simple, soluble molecules(extracellulardigestion )

• Digested products are absorbed by hyphaeMass of hyphae = myceliumSporangium :

produces spores for reproduction

Importance of saprophytesImportance 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 spore 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: The thread-like structures are used for feeding. They are called hyphae which can produce enzymes for digesting the organic food.

Parasitic nutritionParasitic nutrition(Parasitism)(Parasitism)

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

How a tapeworm How a tapeworm obtains its obtains its nutrient?nutrient?

• Live inside the small intestine of human• Food in small intestine is already digestedCan be absorbed

directly through the body wall of tapeworm by diffusion

Structural Structural adaptations of adaptations of

tapewormtapeworm• 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 Structural adaptations of tapewormtapeworm

• Long, flattened body– To increase the surface area for more a

bsorption of digested food by diffusion

•Body covered by cuticle & secretes anti-enzyme

–To protect itself from the attack of digestive enzymes from the host

•Each host can only house one tapeworm because it is too long. -To reproduce by having both male and female reproductive organs (testes and ovaries)

Parasitic nutritionParasitic nutrition(Parasitism)(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

Effect on Host:

To observe a Tapeworm

Does the tapeworm have a mouth ?

Ans: The 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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