(6) Ecosystems Flashcards
Ecosystem
All living organisms and non living components and their interactions
Population
Number of individuals of the same species, living in the same place at the same time.
Community
All the organisms and different species living in a habitat
Habitat
Place organisms live
Niche
Role of an organism in an ecosystem
Trophic level
Stage in a food chain occupied by a particular group of organisms
Biotic factors affecting an ecosystem
Living factors :
Feeding on plants
Predation
Competition - intraspecific and interspecific.
Abiotic factors affecting an ecosystem
Non living components :
Temperature
Oxygen/carbon dioxide concentration
Light intensity
Water supply
pH
Examples of ecosystems
Constantly changing - dynamic, as it is affected by biotic and abiotic factors.
Rock pools - biotic = seaweed as a food source (producer) for consumers, competition can limit organisms in an ecosystem.
Abiotic = tide, pH, temperature - only some organisms can tolerate these changes.
Playing field - biotic = producers attracting other organisms.
Abiotic = rainfall, sunlight.
Large tree - biotic = leaves - food source but also can slow down the growth of the tree when eaten.
Abiotic = drought
Biomass transfer
Organisms in an ecosystem require energy, provided by photosynthesis (productivity), then transferred into chemical energy in plants and transferred to other organisms as food.
Producer fixes carbon using sunlight.
Primary consumer eats producer.
Secondary consumer eats primary consumer then tertiary consumer.
Biomass is the mass of living material, only measuring dry mass allowing the comparison between different organisms (kills them).
Bomb colorimeter - burns the sample in high pressure of o2, rise in temperature of water is measured - some biomass is lost because not all is eaten and some is lost by heat or in faeces.
Net primary production is the energy available at each trophic level.
Gross primary productivity is the total quantity of energy converted in plants.
Efficiency = biomass transferred/biomass intake x100.
Human activities that manipulate the biomass transfer
Killing weeds with herbicides that compete with agricultural crops for energy, increases productivity.
Natural predators introduced to eat pest species, so crops use less energy and biomass, increasing productivity.
Fertilisers provide crops with minerals for growth, replaces lost minerals, so more energy can be used to grow which increases the efficiency of energy conversion.
Rearing livestock intensively and controlling conditions, more energy used for growth and less for other activities. Efficiency and productivity is increased. (animals kept in warm conditions and movement is restricted, given feed higher in energy) Ethical issues.
Recycling - nitrogen cycle
Nitrogen in atmosphere (N2)
nitrogen fixation (rhizobium/azotobacter)
into ammonia then ammonium ions
Ammonium ions into nitrites (NO-2) by nitrosomonas
nitrites into nitrates (NO-3) by nitrobacter.
This is nitrification.
Denitrified back into atmosphere
Or fed into nitrogen compounds in plants, back into ammonia (ammonification)
feeding puts it into animals, death into ammonia by saprobionts.
Recycling - carbon cycle
Plants - photosynthesis takes co2 from air, respiration puts it back in.
Feeding from animals, then co2 respired back into air.
Death from plants or animals (or waste) goes to decomposers.
Then co2 back into air by respiration or burning of fossil fuels.
Sucession
Primary - occurs on newly formed land with no soil present.
Pioneer community - subject to greater change, low biodiversity and biomass, less stable. Can tolerate extreme conditions. Carry out photosynthesis and fix nitrogen.
Intermediate climax community - pioneer species die and add to the soil, able to support grasses and flowering plants which outcompete pioneer species.
Climax community - intermediate species die and add to soils, now able to support larger shrubs and trees. Compete for light, space and nutrients
Secondary - soil present, but no animal or plant species.
Deflected succession - human activity halts the natural flow of succession, preventing it from reaching its climax community.
Sampling to determine variety in ecosystems
Completed many times and calculate mean, avoid recounting, sample at different times of the year and different weather conditions.
Can use quadrats, belt transects (quadrat at specified distances), line transect (counting organisms touching line).
Stratified sampling.
For large animals - looking at droppings (opportunistic sampling)
For small animals - sweep nets, pitfall traps.
