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

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

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

5. Heterotrophic 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

6. 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

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

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

9. 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 (extracellular digestion )
Mass of hyphae = mycelium
Sporangium : produces spores for reproduction

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

11. Investigation 6.1
To observe Mucor

12. 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.

13. 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.

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

15. 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

16. 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

17. Structural adaptations of tapeworm
Long, flattened body
To increase the surface area for more absorption of digested food by diffusion

18. 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)

19. 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

20. Investigation 6.2
To observe a Tapeworm

21. Does the tapeworm have a mouth ?
Ans: The tapeworm does not have a mouth.

22. 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.

23. ~ END ~