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 photosynthesis
Heterotrophic nutrition • depends on other organisms or dead organic matters as their food sources • the organism Heterotrophs • Cannot make their own food andobtain 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 absorbedand 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 • Digested products are absorbed by hyphae • Enzymes digest complex organic molecules in bread into simple, soluble molecules(extracellulardigestion ) Mass of hyphae = mycelium Sporangium : produces spores for reproduction
Enzyme from saprophytes Importance of saprophytes • As decomposers • Allow essential materials (e.g. C, N) to be recycled in the ecosystem Complex organic substances Simple soluble compounds
Investigation 6.1 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 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? • Live inside the small intestine of human • Food in small intestine is already digested Can be absorbed directly through the body wall of tapeworm by diffusion
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 • 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 nutrition(Parasitism) Effect on Host: • 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
Investigation 6.2 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.