Biology Notes for IGCSE 2014
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    • All Notes
    • 01 Classification
    • 02 Cells
    • 03 Enzymes
    • 04 Plant Nutrition
    • 05 Animal Nutrition
    • 06 Plant transport
    • 07 Human transport
    • 08 Respiration
    • 09 Coordination
    • 10 Excretion
    • 11 Homeostasis
    • 12 Reproduction
    • 13 Inheritance
    • 14 Ecosystem
  • Classification
    • Summary
    • Characteristics of Living organisms
    • Classification of Living organisms
    • Kingdoms of Living organisms
    • Animal Kingdom >
      • Classification
      • Phylum Vetebrates
      • Phylum Arthropods
      • Annelids, Nematodes, Molluscs
    • Plant Kingdom
    • Virus
    • Bacteria Kingdom
    • Fungi Kingdom
    • Dichotomous keys
  • Cells
    • Summary
    • Structure
    • Functions
    • Tissues, Organs, Systems
    • Diffusion
    • Osmosis
    • Active transport
  • Enzymes
    • Summary
    • Enzymes and reactions
    • 'Lock and Key' model
    • Role in germinating seeds
    • Use in biological washing powders
    • Use in the food industry
    • Use of microorganisms and fermenter to manufacture enzymes
    • Use of microorganisms to manufacture antibiotic penicillin
  • Nutrition
    • Animal >
      • Summary
      • 1 >
        • Main nutrients: carbohydrates, fats and proteins
        • Food tests >
          • Food test 1 - Starch test
          • Food test 2 - Benedict's test for Reducing Sugars
          • Food test 3 - Emulsion (ethanol) test for Fats
          • Food test 4 - Biuret test for Proteins
        • Other Nutrients: Vitamins, Minerals, Fiber and Water
        • Using yeast to make bread and beer
        • Using microorganism in making yoghurt and single cell protein
        • Food additives - uses, benefits and health hazards
        • Use of modern technology for increasing food production
      • 2 >
        • Problems of world food supplies and the causes of famine
        • Diet
        • Human alimentary canal
        • Human teeth and dental decay
        • Adding fluoride to public water supplies
        • Mechanical and chemical digestion
        • Absorption – function of the small intestine and significance of villi
        • Assimilation and role of the liver
    • Plant >
      • Summary
      • The equation for photosynthesis
      • Photosynthesis investigations - Principles and Starch test
      • Effect of Light intensity on the rate of Photosynthesis
      • Effect of Temperature on the Rate of Photosynthesis
      • Effect of Carbon Dioxide on the Rate of Photosynthesis
      • Limiting factors in photosynthesis
      • Optimum conditions for photosynthesis in Green house
      • Leaf structure
      • Plant's mineral requirements and fertilisers
  • Transport
    • Plant >
      • Summary
      • Functions of xylem and phloem
      • Distribution of Xylem and Phloem in roots, stems and leaves
      • Root hairs and water uptake by plants
      • Passage of water through root, stem and leaf
      • Transpiration in plants and factors affecting tranpiration rate
      • Adaptations of the leaf, stem and root to different environments
      • Translocation of organic foods in plants
      • Translocation of applied chemicals throughout the plant
      • Transport of materials from sources to sinks at different seasons
    • Human >
      • Summary
      • 1 >
        • The circulatory system
        • Structure and function of the heart
        • Effect of exercise on heartbeat and causes of a coronary heart disease
        • Arteries, veins and capillaries - structure and functions
        • Blood composition and Plasma
        • Blood cells - structure and functions
      • 2 >
        • Blood clotting
        • Immune system - antibody, tissue rejection
        • Functions of lymphatic system
        • Respiration
        • Aerobic and anaerobic respiration
        • Gaseous exchange
  • Respiration
    • Summary
    • Definition
    • Aerobic, anaerobic
    • Gaseous exchange
    • Inspired, expired air
    • Tobacco smoke
  • Reproduction
    • Summary
    • Types
    • Plant >
      • Pollination
      • Flower structure
      • Formation of seed
      • Seed dispersal
      • Self-pollination, cross-pollination
      • Growth and development
    • Human >
      • Reproductive system
      • Menstrual cycle
      • Fertilisation
      • Fetus development
      • Birth
      • Sex hormones
      • Birth control
      • Artificial insemination
      • HIV/AIDS
      • Gonorrhoea
      • Breast feeding
  • Coordination
    • Coordination >
      • Summary
      • Hormones, adrenaline
      • Hormones in food production
      • Human nervous system
      • Simple reflex arc
      • Effectors, biceps and triceps
      • Voluntary, involuntary actions
      • The eye, rods and cones
      • Accommodation
      • Tropism in plants
      • Auxins
    • Homeostasis >
      • Summary
      • Homeostasis
      • Blood glucose
      • Negative feedback
      • Kidney structure
      • Kidney function
      • Formation of urea
      • Dialysis
      • Drugs
  • Inheritance
    • Summary
    • Key definitions
    • Chromosomes, DNA
    • Mitosis and Meiosis
    • Monohybrid cross
    • Codominance
    • Continuous, discontinous
    • Mutation, radiation
    • Sickle cell anaemia
    • Selection
    • Antibiotic-resistance bacteria
    • Genetic engineering
  • Ecosystem
    • Summary
    • Human & ecosystem >
      • Human influences
      • Deforestation
      • Water pollution
      • Air pollution
      • Greenhouse gases
      • Pesticides, nuclear fallout
      • Conservation, recycling sewage
    • Energy flow
    • Food chain
    • Food web
    • Food pyramids
    • Energy efficiency
    • Carbon & water cycles
    • Nitrogen cycle
    • Combustion of fossil fuels
    • Population size

#64 Adaptations of the leaf, stem and root 
to different environments


Plants which live in extreme environments have adaptations to control their transpiration rate. Most modifications are adaptations to very dry (arid) environments. Water plants have no problem of water shortage. They do not need adaptations to conserve water as desert plants.  
Picture
Plants modified to cope with a lack of water are called xerophytes. Living in deserts where water is scarce and evaporation is rapid, or in windy habitats where evaporation can also be rapid, they have to cut down water loss. 

    1. Marram grass (Ammophila)

Picture
  • Very long roots to search for water deep down in sand dunes.
  • Leaves that roll up in dry weather to increase humidity around stomata, reducing transpiration. 
  • Sunken stomata to create high humidity and reduce transpiration.
  • Fine hairs around stomata, reducing air movement so humidity builds up and transpiration is reduced. 


Picture
2. Prickly pear cactus (Opuntia)
Picture
  • Leaves reduced to spines – this reduces the surface area for transpiration and also acts as a defence against herbivores.
  • Reduces number of stomata.
  • Stomata cloesed during the day- when conditions for transpiration are most favourable.
  • Fleshy stem - to store water. 

3. Pine tree (Pinus)
Picture
  • Leaves needles-shaped to reduce surface area for transpiration and to resist wind damage.
  • Sunken stomata to create high humidity and reduce transpiration.
  • Thicsk waxy cuticle on the epidermis to prevent evaporation from leaf surface. 
Picture
Water plants may have stomata on the tops of their leaves

Water hyacinth (Eichhornia csassipes)
Picture

  • Roots do not attach to to the bed of the river or pond where they grow, but just float freely in the water. 
  • The stems and leaf stalks have hollow spaces in them, filled with air à   help to float on the top of the water where they can get plenty of light for photosynthesis. 
  • Leaves and stomata are on both surfaces, not just on the underside as in most plant à allow to absorb CO2 from the air, for photosynthesis. 
  • The cuticle on the upper and lower surfaces of the leaves is much thinner than in plants that don't live in water, there is no need to prevent water loss from the leaves. 




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