Adaptions to Nutrition

• Feeding behaviours of multicellular organisms

  • Autotrophic
  • Photoautotrophic
  • Chemoautotrophic
  • Heterotrophic
  • Saprotrophic/saprobiotic
  • Holozoic
  • Parasitic
• Autotrophic


  Organisms which carbon dioxide and water (inorganic molecules) to synthesise organic compounds
• Photoautotrophic


  Organisms which obtain their nutrition through photosynthesis
• Chemoautotrophic


  Organisms which obtain their nutrition through inorganic molecules, such as sulphur
• Heterotrophic


  Organisms which feed on organic compounds produced by other organisms
• Saprotrophic/saprobiotic


  Organisms which secrete enzymes, externally digest food substances and then absorb the products of digestion into the organism e.g. fungi
• Holozoic


  Organisms which internally digest food substances e.g. animals
• Parasitic


  Lives on or in a host
• Digestive systems of multicellular organisms

  • Simple, undifferentiated sac-like gut e.g. Hydra
  • Tube guts with different openings for ingestion and egestion and specialised regions for the digestion of different food substances
• Unicellular organisms


  Absorb food particles and digestion is carried out intracellularly e.g. Amoeba
• Digestion of different foods requires different enzymes (e.g. protease, lipase) and different conditions (e.g. different pH, as different enzymes have different optimum pHs)
• Human gut


  • Adapted to an omnivorous diet, which includes both plant and animal materials
  • Amylase is present in the saliva to digest carbohydrates - this is a characteristic usually found in herbivores
  • The gut is long (like herbivores)
  • The gut lacks fermentation vents (like carnivores)
• Duodenum


  First section of the small intestine where proteins and lipids are broken down, and contains Brunner's glands which produce mucus to protect the duodenum and maintain an alkaline pH optimal for lipase and protease activity
• Ileum


  Last section of the small intestine which doesn't have Brunner's glands
• All sections of the small intestine have folded walls and villi to increase surface area
• Herbivore guts and dentition

  • Strong, flat molars for grinding leaves
  • Small or non-existent canines
  • Teeth grow continuously to help with grinding down food
  • Longer gut
• Ruminants


  Mammals who digest food by fermentation in their stomachs prior to digestion via microbe action, necessary because of a high-cellulose diet. Their stomachs have four areas - the rumen, reticulum, omasum and abomasum
• Carnivore guts and dentition

  • Large canines
  • Much smaller, less bridged molars
  • Eye sockets located to best catch prey (on the side for ambush predators, on the front for persistence predators)
  • Much shorter gut
  • More acidic stomach
  • No amylase in saliva
• Parasites


  Highly specialised organisms which obtain their nutrition at the expense of the host species, e.g. tapeworms living in small intestines and feeding off the host's food, or sucking lice living on fibres and feeding off the host's blood