Ecological niches

ecological niche

• the role of a species in its ecosystem

• niches have biotic/abiotic elements

  • zones of tolerance for abiotic variables determines habitat of a species

  • food supply is biotic, can be autotrophic, heterotrophic, mixotrophic

• unless all the dimensions of the niche are satisfied in an ecosystem, the species won’t be able to survive, grow or reproduce

obligate/ facultative anaerobes and obligate aerobes

• obligate aerobes

  • oxygen must be continuously available for aerobic respiration

• obligate anaerobes

  • conditions must be anaerobic as oxygen kills the organism

• facultative anaerobes

  • oxygen is used if available but anaerobic conditions are tolerated

photosynthesis as nutrition

• energy from sunlight used for fixing carbon dioxide and making carbon compounds

• organisms that use it:

  • plants

  • eukaryotic algae

  • cyanobacteria

holozoic nutrition

• animals obtain supplies of carbon compounds by consuming food

  • heterotrophic, as the carbon compounds come from other organisms

  • food molecules must be swallowed and then digest before they are absorbed - holozoic nutrition

• holozoic nutrition process:

  • ingestion

  • internal digestion

  • absorption

  • assimilation

  • egestion

mixotrophic nutrition

• organisms that aren’t exclusively hetero or autotrophic

  • some protists e.g Euglena are like this

• facultative mixotrophs

  • can be entirely autotrophic, entirely heterotrophic or use both modes

• obligate mixotrophs

  • cannot grow unless they utilise both auto and heterotrophic modes of nutrition

saprotrophic nutrition

• feed on dead organic matter, by secreting digestive enzymes into the matter and digesting them externally

• many types of bacteria & fungi are saprotrophic

archaea - diverse nutrition

• archaea are extremely diverse in their sources of energy for ATP production and carbon

dentition and diet in hominidae

• Hominidae (humans, gorillas, chimps) show a relationship between diet and dentition

  • teeth of herbivores tend to be large and flat to grind plant tissues

  • omnivores tend to have mix of diff teeth to break down meat and plants

  • humans have flat molars in back of mouth to crush and grind food and sharper canines/incisors to tear

NOS theories

• deductions can be made from theories

• hypotheses about diets of extinct species in the Hominidae can be developed from their jaw bone and skull structure

adaptations of herbivores for feeding

• insect mouthparts are diverse but homologous - derived by evolution from a common ancestor

  • leaf-eating insects have jaw-like mouthparts w/ tough mandibles for chewing and piercing

adaptations of plants for resisting herbivory

• adaptations:

  • thorns

  • stings

  • synthesis of secondary metabolites that are toxic to herbivores

    • some herbivores have developed metabolic adaptations to detoxify the toxins

adaptations of predators and prey

• predators:

  • large pointed upper front teeth in bats (structural)

  • venom containing toxins to paralyse prey (chemical)

  • waving of a fin ray in anglerfish to lure prey (behavioural)

• prey

  • swimming in tight groups in fish (behavioural)

adaptations of plants for harvesting light

• in ecosystems where light intensity is the limiting factor for photosynthesis (like in forest), plants compete for light so they have diverse adaptations

  • trees have a dominant leading shoot that grows rapidly up to the forest canopy so no shade from other plants

  • lianas climb other trees, using them for support

  • epiphytes grow on trunks and branches of trees so receive higher light intensity than on forest floor

  • strangler epiphytes climb up tree trunks, encircle them and outgrow the trees branches, shading its leaves

  • shade-tolerant shrubs absorb small amounts of light that reach forest floor

fundamental vs. realised niches

• fundamental niche - the potential of a species based on adaptations and tolerance limits

• in natural ecosystems, there is competition and a species is typically excluded from parts of its fundamental niche by competitors

  • realised niche - extent of a species niche when in competition with other species

competitive exclusion

• when fundamental niches of 2 species overlap, 1 species is expected to exclude the other from that part of its range by competition

• if 2 species have overlapping fundamental niches and 1 species outcompetes in all parts of the fundamental niche, the outcompeted species has no realised niche and is competitively excluded from the whole ecosystem