Modes of nutrition

• what energy can living organisms only use?

  chemical energy
• where do living organisms get their chemical energy from?

  from complex molecules (i.e. food)
• what is the major difference between the many types of living organisms?

  its how they obtain their food
• how do autotrophic organisms obtain their food?

  they make their own food from the simple inorganic raw materials, carbon dioxide and water
• what is an autotroph?

  an organism that synthesises its own complex organic molecules from simpler molecules using either light or chemical energy
• what are the 2 types of autotrophic organisms?

  • photoautotrophic organisms
  • chemoautotrophic organisms
• what are photoautotrophic organisms (photoautotrophs)?

  • they use light as the energy source and perform photosynthesis
  • they are green plants, some protoctista and some bacteria
  • this type of nutrition is described as holophytic
• what are chemoautotrophic organisms (chemoautotrophs)?

  • they use energy from chemical reactions
  • these organisms are all prokaryotes and they perform chemosynthesis
  • this is less efficient than photosynthesis and the organisms that do this are no longer dominant life forms
• how do heterotrophic organisms obtain their food?

  • they cant make their own food and they consume complex organic molecules produced by autotrophs, so they are consumers
  • they either eat autotrophs or organisms that have, themselves eaten autotrophs
  • all animals are consumers and are dependent on producers for food
  • heterotrophs include animals, fungi, some protoctista and some bacteria
• what are examples of heterotrophs?

  • animals
  • fungi
  • some protoctista
  • some bacteria
• what is a heterotroph?

  an organism that obtains complex organic molecules by consuming other organisms
• what uses saprotrophic nutrition?

  by all fungi and some bacteria
• what do saprotrophs (aka saprobionts/saprophytes) feed on?

  they feed on dead or decaying matter
• how do saprotrophs/saprobints digest food?

  • they have no specialised digestive system and they secrete enzymes, including proteases, amylases, lipases and cellulases, onto food material outside the body for extracellular digestion
  • they absorb the soluble products of digestion across their cell membranes by diffusion and active transport
• what are decomposers?

  microscopic saprotrophs and their activities are important in decaying leaf litter and recycling nutrients, such as nitrogen
• what is an example of a decomposer?

  the mould rhizopus, found on rotting fruit
• what is a saprotroph/saprobiont?

  an organism that derives energy and raw materials for growth from the extracellular digestion of dead or decaying material
• what does parasitic nutrition mean?

  it means obtaining nutrition from another living organism, the host
• how does parasitic nutrition work?

  • endoparasite‘s live in the body of the host, while ectoparasites live on its surface
  • a parasite’s host always suffers some harm and often death
• how have parasites adapted?

  they have adapted in many ways and are highly specialised for their way in life
• whats are some examples of parasites?

  • tapeworm (taenia solium)
  • head-lice (pediculus capitis, the human head louse)
  • the fungus causing potato blight
  • plasmodium which causes malaria
• who uses holozoic nutrition?

  most animals
• how does holozoic nutrition work?

  • they ingest food, digest it and egest the indigestible remains
  • the food is processed inside the body, in a specialised digestive system
  • digested material is absorbed into the body tissues and used by the cells
• what are herbivores?

  animals that eat plant material only
• what are carnivores?

  animals that eat other animals only
• what are omnivores?

  animals that eat both plant and animal material
• what are detritivores?

  animals that feed on dead and decaying material
• what is holozoic?

  feeding method of many animals, involving ingestion, digestion, absorption, assimilation and egestion