10.1-10.3

• Abiotic conditions vary enormously
• Abiotic conditions


  • Temperature
  • Humidity
  • Wind and air currents
  • Water currents
  • pH
  • Availability of light
  • Water
  • Nutrient
• Organisms have a specific habitat with specific locality and biotic and abiotic conditions
• Tolerance range


  Organisms can tolerate a certain range of a particular factor, but cannot survive if there is too much or too little of the factor
• Organisms with genetic variations that allow them to best exploit a set of environmental conditions will survive in that habitat
• Types of adaptations that increase survival

  • Structural
  • Behavioural
  • Physiological
• Structural adaptations


  • Physical features such as glands that can secrete excess water in rainforest trees
  • Very short ears and other extremities in animals living in very cold habitats
• Behavioural adaptations


  • Changes in the way an organism behaves, such as animals congregating close together to share body heat in very cold weather
• Physiological adaptations


  • The ability to regulate the cells or tissues within a system, such as blood flow in the outer body areas, to maintain a constant internal environment
• Environmental factors of particular significance

  • Temperature
  • Water availability
• Abiotic Factors


  Non-living factors that impact an ecosystem
• The more active the animal

  The higher its core temperature
• The core temperature of active animals

  Is higher than the air temperature of the habitat in which they live
• How quickly heat is lost is dependent on the temperature gradient
• The bigger the gradient


  The faster heat is lost
• Animals with a large surface area to volume ratio will lose heat faster
• A tall, slender animal (emu)


  Will lose heat faster than a small, compact animal (finch)
• Animals can reduce the loss of heat from their bodies by lowering the temperature in their limbs
• Lowering the temperature in limbs

  Decreases the temperature gradient between the large surface area limbs and the environment
• Ways to lower the temperature of limbs

  1. Arterioles constrict

  2. Blood flow to skin reduced

  3. Blood bypasses skin capillaries

  4. Counter-current system in blood vessels
• Counter-current system


  • Arrangement of blood vessels passing to the extremities of cold-habitat animals
• How Hair/Feathers Reduce Heat Loss

  • Can be raised by contraction of erector muscles
  • Increases insulating layer of trapped air
  • Air is a poor conductor of heat
• How Insulation Reduces Heat Loss

  • Via subcutaneous fat layers
  • Thick hair or feathers
• Thermogenesis


  The animal creating its own body heat as opposed to relying on external sources
• Increasing heat production


  1. Increasing contraction of muscles

  2. Secretion of hormones that increase metabolic rate
• Some mammals have brown adipose tissue that is specialised for rapid heat production
• Brown fat cells


  Store lipids and contain large numbers of mitochondria
• Thermoregulatory mechanisms


  • Changing behaviour
  • Increasing metabolic heat production
  • Controlling exchange of heat with environment
• Kleptothermy


  Used to reduce heat loss by groups huddling together to share body heat
• Kleptothermy delays reproduction to ensure the offspring are born when food is available
• Kleptothermy occurs in endotherms and ectotherms
• Torpor


  A state of decreased metabolic rate, slow heart and respiratory rate, and less responsiveness
• Torpor occurs in cold areas when food is scarce
• Controlled state of torpor

  1. Period of fattening

  2. Preparation of a nest
• Some animals' period of torpor may last only a day but others it can last several
• Hibernation


  Occurs in extreme cold environments with decreased body temperature and long-term inactivity
• Hibernation


  • Rate of metabolic processes decreases
  • Less energy needed
  • Stores reserves of fat to be readily metabolised at low temperatures
  • Blood flow redirected towards major organs
• Aestivation


  A prolonged torpor which occurs in a hot, dry environment when water supply is low
• Aestivation


  • Inactivity and lowered metabolic rate
  • Electrical activity in the brain stops, but the animal still responds to stimuli
• A high surface area to volume ratio in cold climates would result in a high heat loss