B4.2

• Between the two coral heads is a crown of thorns sea star. These predators graze the corals. If too successful they will change the community structure of the reef so that it becomes dominated by algae rather than coral. This in turn forces the sea star to migrate to other reefs where coral dominates the community structure.
• Ecological niche


  The role of a species in an ecosystem, including the biotic and abiotic interactions that influence growth, survival and reproduction, including how a species obtains food
• Obligate anaerobes


  • Lack enzymes to process oxygen
• Facultative anaerobes


  • Normally respire aerobically but can switch to anaerobic if no oxygen available
• Obligate aerobes


  • Requires oxygen as final electron acceptor for respiration
• Photosynthesis


  The mode of nutrition in plants, algae and several groups of photosynthetic prokaryotes
• Holozoic nutrition


  In animals, food is ingested, digested internally, absorbed and assimilated
• Mixotrophic nutrition


  In some protists, they are both autotrophic and heterotrophic
• Saprotrophic nutrition


  In some fungi and bacteria, they secrete digestive enzymes onto non-living organic matter and absorb the products of digestion
• Archaea


  • One of the three domains of life, metabolically very diverse, using light, oxidation of inorganic chemicals or oxidation of carbon compounds to provide energy for ATP production
• Dentition


  The relationship between the teeth and the diet of omnivorous and herbivorous members of the Hominidae family
• Herbivore adaptations


  • Piercing and chewing mouthparts of leaf-eating insects, plants resist herbivory using thorns and other physical structures, plants produce toxic secondary compounds, some animals have metabolic adaptations for detoxifying these toxins
• Predator and prey adaptations

  • Chemical, physical and behavioural adaptations
• Plant adaptations for harvesting light

  • Examples from forest ecosystems including trees reaching the canopy, lianas, epiphytes, shade-tolerant shrubs and herbs
• Fundamental niche


  The potential of a species based on adaptations and tolerance limits
• Realized niche


  The actual extent of a species' niche when in competition with other species
• Competitive exclusion


  Elimination of one of the competing species or the restriction of both to a part of their fundamental niche
• Categories of interspecific relationships within communities

  • Herbivory
  • Predation
  • Interspecific competition
  • Mutualism
  • Parasitism
  • Pathogenicity
• Mixotrophs


  Organisms that use both autotrophic and heterotrophic modes of nutrition
• Types of mixotrophs


  • Obligate mixotrophs
  • Facultative mixotrophs
• Obligate mixotrophs


  Always use both forms of nutrition (auto and heterotroph)
• Facultative mixotrophs


  Will switch modes based on need
• Saprotrophs


  Organisms that live on, or in, non-living organic matter and secrete digestive enzymes to absorb the products of digestion
• Unlike most heterotrophs, saprotrophs are not consumers as they do not ingest food: digestion is external as enzymes are secreted
• Saprotrophs


  • Bacteria
  • Fungi
• Decomposers


  Organisms that facilitate the breakdown of organic material
• Domains of life


  • Archaea
  • Bacteria (Eubacteria)
• Nutritional modes of archaea

  • Chemoautotrophs
  • Halophiles
  • Photoautotrophs
• Archaea


  • Staphylococcus aureus
  • Cyanobacteria sp.
  • Rhizobium sp.
• Archaea


  • No nucleus
  • Unicellular
  • Polysaccharides in cell wall
  • Extremophiles
  • Histone protein
• Bacteria (Eubacteria)


  • No nucleus
  • Unicellular
  • Peptidoglycan in cell wall
  • No histone proteins
• Herbivores


  Organisms that eat a plant-based diet, often with tough fibrous plants that require a lot of chewing/grinding before swallowing
• Omnivores


  Organisms that eat a plant and meat diet, needing more flexibility to tear food (meat) and grind plants
• Family Hominidae (Hominids)


  • Orangutans
  • Gorillas
  • Chimpanzees
  • Humans (plus extinct predecessors)
• Characteristics shared by all hominids

  • No tail
  • Relatively flat face and 3D vision
  • Same dentition (number of teeth)
  • Fully opposable first digits
• Incisors


  Sharp teeth for cutting
• Molars


  Large, strong teeth for grinding
• As humans began to cook food

  It became softer so smaller teeth (and jaw) are selected for, and smaller muscles are required to control jaw movements
• Extinct hominid jaws


  • Herbivore
  • Omnivore
  • Herbivore
  • Omnivore
• By studying vestigial organs and observing the dentition in living mammals and the diet they consume including herbivores, carnivores and omnivores we can infer diet in fossils based on their dentition