12: interactions within ecosystems

• Abiotic factors

  ( physical and chemical factors )

  1. Light intensity
  2. temperature
  3. water availability
  4. pH of water and moist soil
  5. salinity of water and moist soil
  6. dissolved oxygen content in aquatic habitats
• Biotic factors

  ( related to living things )

  1. Presence of producers, consumers and decomposers
  2. structural adaptations of organisms
  3. behavioural adaptations of organisms
• Wood equation of photosynthesis

  Carbon dioxide + water -> ( w light energy and chlorophyll) -> glucose + oxygen

  Light intensity must be sufficient for this reaction to take place
• salinity of water or moist soil

  Salinity refers to the concentration of salts in water, or the

  moisture content in the soil.

  The higher the salinity, the lower the water potential of the

  water, and vice versa. Water potential of the surrounding water affects how an organism’s cells gain or lose water.
• dissolved oxygen content

  Oxygen content must be sufficient for organisms to respire aerobically to release energy.

  Energy is needed for many activities such as

  • Muscular contraction

  • Cell division
• Water availability

  major component of living cells (especially cytoplasm)

  • medium for chemical reactions to take place

  • raw material of photosynthesis

  • exerts turgor pressure in plant cells, providing structural

  support to plant tissues
• Parasitism

  is a relationship involving one organism gaining benefit, while harming the other organism.
• Commensalism

  Involves one species deriving benefit while the other species is unaffected
• Mutualism


  Is a relationship where both species benefit from one another
• Trophic levels

  1. Producers
  2. private consumers
  3. secondary consumers
  4. tertiary consumers
• A producer

  absorbs light energy from the sun, and converts the light energy to chemical energy stored in glucose molecules.
• How does food become energy

  After a consumer ingests food, the food is digested and absorbed into the bloodstream. Then, the digested food is transported by the blood to all of the body’s cells.

  Glucose molecules are broken down in mitochondria of cells, in a process called aerobic respiration. Energy is released in this process.
• word equation of respiration

  Glucose + oxygen -> water + carbon dioxide + large amount of energy
• How do decomposes obtain energy


  By breaking down the remains of dead organisms into simpler substances, for their own respiration.
• Loss of Energy Along Food Chains

  There is a loss of 90%
• How is energy lost along food chains

  Undigested food

  • some parts of an animal cannot be digested hence the energy is not transferred to the predator like fur

  uningested food

  • not all parts of the animal is eaten by the predator like bones

  loss as heat

  • some energy is used by rabbit for movement, reproduction and lost as heat during respiration. energy is thus lost to the environment