Science · Class 10 · Life Processes
Nutrition in Living Organisms
Aim: Understand how living organisms obtain and use nutrients, and compare autotrophic and heterotrophic modes of nutrition.
- Nutrition — the process of taking in food and using it for growth, repair, and energy
- Autotrophic — able to make own food (e.g. green plants)
- Heterotrophic — depends on other organisms for food
- Photosynthesis — process by which plants make food using sunlight
- Stomata — pores on leaves for gas exchange
Life Processes · Concept 1 of 8
Why do organisms need food?
- To release energy for life processes (movement, growth, repair)
- To build and repair body tissues
- To maintain a steady internal environment
Life Processes · Concept 2 of 8
Two modes of nutrition
- Autotrophic — organism makes its own food (green plants, some bacteria)
- Heterotrophic — organism obtains food from other organisms (animals, fungi, most bacteria)
Life Processes · Concept 3 of 8
Photosynthesis — the raw materials
- Carbon dioxide, absorbed from air through stomata
- Water, absorbed from soil by roots
- Sunlight, captured by chlorophyll in leaves
- Overall word equation: CO2 + H2O --(sunlight, chlorophyll)--> Glucose + O2
Life Processes · Concept 4 of 8
Where does photosynthesis happen?
- Mainly in leaves, inside cells containing chloroplasts
- Chlorophyll gives leaves their green colour and absorbs light energy
- Stomata open and close to control gas exchange and water loss
Life Processes · Concept 5 of 8
Heterotrophic nutrition — three types
- Saprophytic — feeding on dead and decaying matter (e.g. fungi like bread mould)
- Parasitic — feeding on a living host, often harming it (e.g. Cuscuta, tapeworm)
- Holozoic — taking in whole food and digesting it internally (most animals, including humans)
Life Processes · Concept 6 of 8
Steps of holozoic nutrition
- Ingestion — taking food into the body
- Digestion — breaking food into simpler, absorbable molecules
- Absorption — digested food enters blood/cells
- Assimilation — absorbed food used for energy, growth, repair
- Egestion — undigested waste removed from the body
Life Processes · Concept 7 of 8
Human digestion — a quick tour
- Mouth: saliva starts starch digestion
- Stomach: acid + enzymes digest proteins
- Small intestine: bile and enzymes complete digestion; nutrients absorbed
- Large intestine: water absorbed; waste compacted for egestion
Life Processes · Concept 8 of 8
Why comparing nutrition modes matters
- Explains the roles plants and animals play in an ecosystem
- Plants form the base of almost every food chain
- Sets up the next topic: respiration and how energy from food is released
Quick Recap
Check Your Understanding
- 1What are the raw materials needed for photosynthesis, and where does the process mainly occur?
- 2Name the three types of heterotrophic nutrition and give one example of each.
- 3List the five steps of holozoic nutrition in the correct order.