VCE Biology Unit 1 AOS 2 – How do plant and
animal systems function?
1. From Cells to Systems
• Hierarchy: Cell → Tissue → Organ → System → Organism
• Animal tissues: Epithelial (lining/protection), Muscle (movement: skeletal, smooth, cardiac), Nervous
(neurons, glia), Connective (support: bone, cartilage, blood, fat)
• Organs: Multiple tissues for a specific function
• Systems: Groups of organs working together (e.g., digestive, excretory, endocrine)
• Plant tissues: Dermal (outer), Ground (photosynthesis/storage), Vascular (xylem/phloem)
2. Plant Vascular Tissues & Water Balance
• Xylem: Transports water/minerals from root to leaf. Dead, lignified, hollow cells. Water moves by root
pressure, adhesion, cohesion, transpiration pull.
• Phloem: Transports sugars from leaves to other parts (source to sink). Living sieve tubes &
companion cells. Movement by pressure-flow (active loading, osmosis draws in water, pressure
moves sap).
• Vascular bundles: Xylem + phloem in roots, stems, leaves. Cambium in between.
• Transpiration stream: Water flow from roots to leaves, driven by evaporation at leaf surface
(stomata).
• Stomata: Pores controlled by guard cells. Regulate gas exchange and water loss.
• Turgor: Water pressure in guard cells opens/closes stomata.
• Adaptations: Leaf hairs, waxy cuticle, sunken stomata, closing stomata in heat/drought.
3. The Digestive System
• Purpose: Breakdown (digestion) & absorption of nutrients
• Digestion: Mechanical (chewing, churning, emulsification) & Chemical (enzymes break
macromolecules into subunits)
• Major organs:
• Mouth: Chews, saliva (amylase—starch)
• Oesophagus: Peristalsis moves food
• Stomach: Churns, acid, pepsin (protein)
• Small intestine: Enzymatic digestion (amylase, lipase, protease), absorption (villi, microvilli)
• Pancreas: Enzymes, bicarbonate
• Liver: Bile (emulsifies lipids), detox, glycogen storage
• Gall bladder: Stores/releases bile
• Large intestine: Absorbs water, stores waste, gut flora
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animal systems function?
1. From Cells to Systems
• Hierarchy: Cell → Tissue → Organ → System → Organism
• Animal tissues: Epithelial (lining/protection), Muscle (movement: skeletal, smooth, cardiac), Nervous
(neurons, glia), Connective (support: bone, cartilage, blood, fat)
• Organs: Multiple tissues for a specific function
• Systems: Groups of organs working together (e.g., digestive, excretory, endocrine)
• Plant tissues: Dermal (outer), Ground (photosynthesis/storage), Vascular (xylem/phloem)
2. Plant Vascular Tissues & Water Balance
• Xylem: Transports water/minerals from root to leaf. Dead, lignified, hollow cells. Water moves by root
pressure, adhesion, cohesion, transpiration pull.
• Phloem: Transports sugars from leaves to other parts (source to sink). Living sieve tubes &
companion cells. Movement by pressure-flow (active loading, osmosis draws in water, pressure
moves sap).
• Vascular bundles: Xylem + phloem in roots, stems, leaves. Cambium in between.
• Transpiration stream: Water flow from roots to leaves, driven by evaporation at leaf surface
(stomata).
• Stomata: Pores controlled by guard cells. Regulate gas exchange and water loss.
• Turgor: Water pressure in guard cells opens/closes stomata.
• Adaptations: Leaf hairs, waxy cuticle, sunken stomata, closing stomata in heat/drought.
3. The Digestive System
• Purpose: Breakdown (digestion) & absorption of nutrients
• Digestion: Mechanical (chewing, churning, emulsification) & Chemical (enzymes break
macromolecules into subunits)
• Major organs:
• Mouth: Chews, saliva (amylase—starch)
• Oesophagus: Peristalsis moves food
• Stomach: Churns, acid, pepsin (protein)
• Small intestine: Enzymatic digestion (amylase, lipase, protease), absorption (villi, microvilli)
• Pancreas: Enzymes, bicarbonate
• Liver: Bile (emulsifies lipids), detox, glycogen storage
• Gall bladder: Stores/releases bile
• Large intestine: Absorbs water, stores waste, gut flora
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