biology

• B4.2 Ecological Niches
• Theme: Form and Function
• First Exams 2025
• Level of Organisation: Ecosystems
• IB Guiding Questions


  • What are the advantages of specialized modes of nutrition to living organisms?
  • How are the adaptations of a species related to its niche in an ecosystem?
• Ecological niche


  The role of a species in an ecosystem
• Differences between organisms


  • Obligate anaerobes
  • Facultative anaerobes
  • Obligate aerobes
• Photosynthesis


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


  A form of heterotrophic nutrition in animals
• Mixotrophic nutrition


  A mode of nutrition in some protists
• Saprotrophic nutrition


  A mode of nutrition in some fungi and bacteria
• Diversity of nutrition


  In archaea
• Relationship between dentition


  The diet of omnivorous and herbivorous representative members of the family Hominidae
• Adaptations of herbivores


  For feeding on plants and of plants for resisting herbivory
• Adaptations of predators


  For finding, catching and killing prey and of prey animals for resisting predation
• Fundamental niche


  The niche an organism could potentially occupy
• Realized niche


  The niche an organism actually occupies
• Competitive exclusion


  The principle that two species competing for the same resources cannot coexist
• Every species of organism is adapted to a unique niche in an ecosystem
• Biotic and abiotic factors that affect

  • Growth of individuals
  • Survival of individuals
  • Ability to reproduce
  • Mode of nutrition
  • Interactions with other species
  • Interactions with its own species
• Oxygen is an abiotic factor that determines where an organism can live
• Obligate anaerobes


  Cannot survive in the presence of oxygen
• Facultative anaerobes


  Can survive in the presence or absence of oxygen
• Obligate aerobes


  Cannot survive in the absence of oxygen
• Photosynthesis is the production of organic compounds in cells using light energy
• Photosynthetic organisms convert carbon dioxide and water using light energy into organic compounds, such as glucose, and oxygen gas
• All animals are heterotrophic
• Holozoic nutrition


  Food is ingested, digested internally, absorbed and assimilated
• Euglena is a well-known freshwater example of a protist that is both autotrophic and heterotrophic
• Mixotrophs


  Can behave as an autotroph and as a heterotroph
• Saprotrophs


  Heterotrophs that obtain nutrients by external digestion of food
• Saprotrophic bacteria and fungi are referred to as decomposers
• Many archaea live in extreme environments such as hot springs
• Archaea are one of the three domains of life
• Archaea are prokaryotes that are found in a wide variety of environments
• Phototrophs


  Some archaea use light energy to produce ATP
• Chemolithotrophs


  Some archaea oxidize inorganic compounds to produce ATP
• Organotrophs


  Some archaea oxidize organic compounds to produce ATP
• Examples of hominids


  • Homo sapiens
  • Homo floresiensis
  • Paranthropus robustus
• Family Hominidae is the family of the great apes, which are all tailless primates