Conditions and Resources Flashcards
Conditions
Conditions – abiotic environmental factors
Influence the functioning of an organism – temp, pH, salinity, humidity
Can be modified by the presence of another organism – e.g under a forest canopy
Conditions cannot be consumed or used up unlike resources
Optimum conditions – those under which most offspring are produced
Often measure effect on key properties – enzyme activity, growth/reproductive rate of individuals
Organisms can survive over a range of conditions
Any condition that approaches/exceeds the limits of tolerance is said to be a limiting condition or factor (Odum, 1955)
When a species is limited in distribution it is said to be restricted according to environmental tolerances
Response curves
R = reproduction, G = growth, S = survival
a) Extremes lethal, only optimum conditions allow reproduction – e.g temp and pH
b) Condition only lethal at high intensities – e.g toxins and chemical pollutants
c) Same as above but condition required as a resource at low concentrations – e.g NaCl or essential elements Cu, Zn, Mn
Temperature and organisms
Other organisms do not perceive their environments as we do
Influences metabolism, growth (linear), development (linear) and size
Important to - understand the role of temp ion seasonal, annual and geographic variations in productivity of ecosystems, know the effects of a rise in global temp, appreciate the knock on consequences
Endotherms – regulate temperature by production of heat within their own bodies (uses more energy)
Ectotherms – rely on external heat sources
Eurythermal – can tolerate wide range of conditions
Stenothermal – cannot tolerate wide range of conditions
Life at low temp – chilling damages membrane permeability, freezing affects osmoregulation, freeze-avoidance and freeze-tolerance adaptations, acclimatisation – natural adaptation to temperature changes
Life at high temp – fire and lightening strikes, thermal vents, hot springs
Temperature can act as a stimulus
Temperate and arctic alpine plants – period of freezing stimulates germination
Interacts with photoperiod and therefore onset of growth
Egg laying stimulated by temperature and day length
Temperature stimulates breeding in many animal species
Temperature strongly affects distribution and diversity of plant and animal species
Temperature interactions – humidity and disease
pH of soil and water and organisms
pH can exert a powerful influence on the abundance and distribution of organisms
Roots damaged by toxic concentrations of H+ (acidic pH) or OH- (basic pH)
Indirect effects occur – soil pH influences nutrient availability and toxin concentration
Acidic soil – high Al3+, Mn2+, Fe3+
Alkaline soil – PO4^3-, Mn2+, Fe3+ insoluble
Soil pH influences plant species – acidic = low species diversity, limestone = high species diversity
Prokaryotes can tolerate extremes of acidity and alkalinity
Geothermal springs, volcanic lakes = sulphur-oxidising bacteria - optimum pH between 2 and 4
Soda lakes = cyanobacteria – optimum pH between 9 and 11
Salinity and organisms
Salt concentration in soils offers osmotic resistance to water uptake by plants
Halophytes – adapted to saline conditions by (e.g) maintaining osmolytes within vacuoles
In marine habitats organisms are usually isotonic
Osmoregulation – maintenance of homeostasis
Physical forces and organisms
Wind and water
Streams and rivers – water shallow and turbulent upstream, fast-flowing downstream
Sea – currents and waves
Organisms have physical adaptations to cope
Climate change and organisms
CO2 has risen since the industrial revolution driving planetary warming rates about 100x faster than post-glacial warming
Many species cannot respond as quickly
Distribution shifts and widespread extinctions of flora and fauna are predicted
Fragmented and developed landscapes are barriers to range shifts
Resources
Resources – all things consumed by an organism. Entities required by an organism that may be reduced by the activities of other organisms
Photosynthetic autotrophs – green plants and algae
Chemosynthetic autotrophs – bacteria and archaea
All other organisms use the bodies of other organisms as food sources
In each case the consumed resource is no longer available to another consumer
The consequence is competition
Other dimensions of the ecological niche
Green plants assemble inorganic resources into organic compounds through photosynthesis
CO2, H2O and sunlight converted into biomass
Consumers reassemble these packages at each successive stage in a web of consumer-resource interactions
Solar energy and organisms
Must penetrate the atmosphere
Absorption, reflection and scattering by water vapour, water surfaces, clouds, atmospheric particles
Varies with circumstance – latitude, season, time of day
Solar radiation is the only source of energy green plants and algae can use
A resource continuum of different wavelengths PAR 400 to 700 nm
Radiation intensity and quality varies continuously
Shade effects – resource depletion
Woodland canopy
Light attenuation by phytoplankton
Carbon dioxide and organisms
Used in photosynthesis, obtained in atmosphere
Availability to plants and algae varies according to position in habitat/water column
C3, C4 and CAM photosynthetic pathways
Water and organisms
Critical resource
Hydration necessary for metabolic reactions
Must be replenished
Plants and transpiration stream
Terrestrial animals drink water or generate it from metabolism of food and body materials
Mineral nutrients and organisms
Macronutrients
Trace elements
Plants obtain nutrients in inorganic forms from soil or water
Some groups have special requirements – diatoms (Si)
Animals obtain nutrients as organic forms in their food
Oxygen and organisms
Diffusion and solubility of O2 is low in water
Limiting in aquatic and waterlogged environments
Aquatic plants modify their roots and shoots
Aquatic animals must either – maintain constant flow over respiratory surfaces, have large SA:V, have specialised respiratory surfaces, lower respiration rate / have specialised pigments
Organisms
Autotrophs assimilate inorganic resources into organic packages consumed by heterotrophs
Grazers – take part of their prey, the remainder may regenerate
Saprotrophs – use dead organisms / waste products as food
Predators – kill other organisms as food resources
Parasites – feed from host but do not kill it
Generalists are polypagous – take a wide variety of prey species
Specialists may be monophagous or polyphagous – specialises on certain parts of prey
Resource-use patterns reflect consumer lifespan
Must match food demands to prey timetable
Evolution of specialised structures e.g mouthparts allow efficient feeding
Nutritional content of plans and animals are very different
Consequences for the consumer
Plant cells rich in cellulose and lignin (carbon)
Animal cells rich in protein (nitrogen)
Physical and chemical defences
Behavioural and morphological defences
The ecological niche
The ecological niche – the framework which each condition should be understood
A niche is not a place, it is an idea – a summary of an organisms tolerances and requirements. Niche describes how, rather than just where, an organism lives
Any condition that approaches/exceeds the limits of tolerance is said to be a limiting condition or factor (Odum 1955)
When a species is limited in distribution it is said to be restricted according to environmental tolerances
A multi-dimensional hypervolume of resource axes (Hutchinson, 1957) – temperature is one dimension, relative humidity, pH, wind speed, flow rate, salinity
The realised niche: Where an organism actually lives, when competitors reduce resources available
Dimensions of the niche
- Includes both conditions and resources
- Conditions usually considered as continuous variables
- Some resource dimensions can be plotted like condition dimensions; upper and lower limits
- Predators can only handle a certain prey size but many resources are discrete entities not continuous variables
- Certain species can only use limited resources – e.g specific insect host plants
- Therefore have to consider a discrete host factor
