MY BIO NOTES

• Plant Organs

  • Roots
  • Leaves
  • Stems
• Roots

  Absorb water & mineral ions
• Leaves

  • Carry out Photosynthesis
  • Transport substances
• Stems

  • Transport substances
• The leaf contains different features
• Leaf features

  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Xylem
  • Phloem
• Upper epidermis

  • Transparent, allows light through to photosynthesise
  • Covered in thin waxy layer to reduce water loss
• Stomata

  • Allow CO2 to enter and O2 to leave
  • Help control amount of water vapour leaving
• Guard cells

  • On either side of stomata
• Palisade mesophyll

  • Contains many chloroplasts
• Spongy mesophyll

  • Full of air spaces to allow gas exchange
• Xylem

  Transports water and mineral ions from roots to leaves
• Phloem

  Transports food (sugars) produced in leaves to rest of plant
• Meristem tissue


  Found at growing tips, contains stem cells that can differentiate
• Photosynthesis takes place in the leaves of plants
• Photosynthesis

  The process plants use to trap light energy
• Photosynthesis

  1. Light absorption

  2. Carbon dioxide + water -> glucose + oxygen
• As light intensity increases

  Rate of photosynthesis increases
• As CO2 concentration increases

  Rate of photosynthesis increases
• As temperature increases

  Rate of photosynthesis increases (up to an optimum)
• Products of photosynthesis

  • Glucose
  • Starch
  • Fats
  • Cellulose
  • Amino acids
• Plants can store starch as a long-term energy store
• Tobacco mosaic virus (TMV)

  Very widespread plant infection that causes leaves to discolour and reduces photosynthesis
• Black spot

  Fungal disease that causes leaves to develop purple/black spots, reducing photosynthesis and growth
• Aphids extract nutrients from plants, reducing their growth
• Ways to diagnose plant disease

  • Look for discolouration
  • Look for spots on leaves
  • Look for stunted growth
• Plant defence responses


  • Physical
  • Chemical
  • Mechanical
• Physical defences

  • Cellulose cell walls
  • Bark
  • Thorns
• Chemical defences

  • Release antibacterial chemicals
  • Release poisons to deter herbivores
• Mechanical defences

  • Sharp thorns to directly protect
  • Irritating hairs
• Humans have a double circulatory system
• Double circulatory system

  1. Deoxygenated blood flows to heart

  2. Pumped to lungs to pick up oxygen

  3. Oxygenated blood flows back to heart

  4. Pumped to body organs
• Arteries

  Carry blood away from the heart
• Veins

  Carry blood back to the heart
• Capillaries

  Where oxygen and nutrients leave the blood, and CO2 enters
• Coronary arteries

  Wrap around the heart to supply it with oxygenated blood
• Red blood cells


  Carry oxygen from lungs to body tissues
• Red blood cells


  • Don't have nucleus
  • More space for haemoglobin
• Shape of red blood cells

  Biconcave, large surface area for oxygen
• White blood cells

  Engulf and destroy pathogens