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When it comes to AS/A-level Biology, do you remember what is autotrophic and heterotrophic nutrition?
Autotrophic Nutrition
- Use external sources of energy (energy from sun or chemical reactions) in the synthesis of organic food materials.
- Autotrophs are the producers in the ecosystem.
(a) Photosynthetic autotrophs - obtain energy from suns radiation which is used to build essential organic compounds from inorganic molecules by the process of photosynthesis.
- They contain pigment, chlorophyll, to absorb light energy.
- E.g. algae, green plants
6CO2 + 6H2O → C6H12O6 + 6O2
(b) Chemosynthetic autotrophs - use energy from certain chemical reactions to synthesise organic molecules from inorganic molecules.
- E.g. nitrifying bacteria – Nitrosomonas and Nitrobacter
Heterotrophic Nutrition
- Heterotrophs must be supplied with readymade organic compound from which to derive their energy.
- Heterotrophs are the consumers.
Types of heterotrophic nutrition
- Holozoic nutrition
- Saprobiontic nutrition - feed on dead material
- Mutualistic nutrition - 2 or more organisms associated with each other. Both contribute and benefit from relationship.
- Parasitic nutrition - feed on living host
1. Holozoic Nutrition
- Characteristic of higher animals including humans.
- It involves feeding on organic matter from the bodies of other organisms.
- There are 5 stages to holozoic nutrition:
- Ingestion - taking food into the mouth
- Digestion - mechanical and chemical breakdown of food (chewing and mixing with enzymes)
- Absorption - small, soluble molecules taken into the bloodstream
- Assimilation - use of absorbed products
- Egestion - getting rid of undigested parts of food
2. Saprobiontic Nutrition
- Organisms feed on dead/ decayed matter.
- Do this by secreting enzymes to digest the material (lipase, protease, and carbohydrase etc.) and then absorbs nutrients from the digested organic matter.
- Digestion is classed as extracellular.
- Saprobionts have no digestive system of their own.
- E.g. Bacteria and fungi
For example,
Rhizopus Stolonifera
- Also known as pin mould.
- Found on bread.
- Immature stage - cotton-like structures.
- Mature stage - produces stalks with heads used to spread spores.
- Rhizoids- ‘roots’ penetrate organic matter and secretes digestive enzymes and absorbs nutrients. (Also known as rhizoid hyphae)
- Hyphae - ‘stalks’ of a mould or fungus. Joined by stolon.
- Sporangia - mature hyphae topped by spores.
- Aseptae - hyphae unjoined by cross walls
- Septae - hyphae joined by cross walls.
- Stolon - external hyphae connecting other hyphae.
Drafted by Bonnie (Biology)