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Understanding Abiotic and Biotic Factors in Ecosystems: Key Influences on Organisms

This text explores abiotic and biotic factors that shape ecosystems and influence organismal behavior. Abiotic factors include light, temperature, water, and chemical composition, affecting how organisms respond to their environment. Biotic interactions, such as competition and symbiosis, define relationships within and between species. Adaptations allow organisms to thrive in their environments, ensuring survival and reproduction. Understanding these dynamics is crucial for studying ecological interactions and the impact of environmental changes.

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Understanding Abiotic and Biotic Factors in Ecosystems: Key Influences on Organisms

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  1. The Environment • Abiotic factors – the physical factors in the environment that can act as the stimuli for the organisms’ responses. • Prefixes: • Light (photo-) - intensity, colour, direction, duration • Gravity (geo-, gravi- in some texts) - up, down, orientation in space

  2. The Environment • Temperature (thermo-) - average and range • Water (hydro-) - humidity, salinity, depth, average rainfall, turbidity, speed of current • Current (rheo-) - align with current

  3. Chemical (chemo-) - CO2, O2, salinity, pH, pheromones, toxins, inorganic nutrients, Macro/micronutrients • Touch (thigmo-) - response to solid objects • Sound – pitch, loudness, range • Pressure – ocean depths, atmosphere, weather pattern formation

  4. Wind – velocity, gustiness, direction • Substrate – composition • Fire - recycling nutrients, seed germination

  5. Adaptations • Adaptations are features that help an organism to make the most of the opportunities provided by the environment. • Organisms with adaptations more suited to the environment are more likely, through the process of natural selection, to pass on their genes to the next generation.

  6. -Structural – morphological, e.g. colour, appendages -Physiological – biochemical/metabolic e.g. hormones -Behavioural – responses to the environment e.g. diurnal, aggression, courtship -Life History – reproductive strategies for survival

  7. Tolerance • Narrow range of physical factors that makes up the optimal range of tolerance for most organisms. If a factor is to extreme in either direction the organism suffers from physiological stress. • If a factor becomes too extreme (too high/too low) the environmental condition leads to death.

  8. Many animal and plant behaviours are to ensure the organism maintains an optimal condition for survival and ultimately reproduction • Animals must detect and be able to respond to key physical factor changes in their environment

  9. Biotic Factors – all relationships between members of the same species (intraspecific) and with members of other species (interspecific) Intraspecific relationships: Competition – for same resources; food, space, light, water, nesting sites, territory, nutrients etc

  10. Reproduction – availability of mates, competition between males, courtship, pair-bond formation, parental care Aggressive interactions - territories, hierarchies Co-operative interactions – group formation for defence (prevent predation/grazing), aid survival (hunt in packs)

  11. Biotic Factors – • Interspecific relationships: • Competition – for same resources; food, space, light, water, nesting sites, territory, nutrients etc • Predator / prey relationships • Plant / Animal – grazers, browsers • Succession – replacement of one species by another over time, each species modifying the environment to allow the new species to be established

  12. Stratification – vertical relationships in space with other organisms • Zonation – bands of organisms that form in relation to a gradient in a major environmental factor • Animal / Animal • Plant / Plant

  13. Symbiosis – variety of interactions involving close species contact. • Involves a host and a symbiot. • Mutualism (cooperation) - both species benefit • Commensalism - one species benefits, the other is unaffected

  14. Parasitism (exploitation) - one species benefits, the other is harmed • Competition - neither species benefits • Neutralism - both species are unaffected • Note: endoparasites – live in the host • ectoparasites – live on the host

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