6.3.1 Ecosystems Flashcards
What is an ecosystem
A habitat and all the biotic and abiotic factors which influence it
What are saprobionts
Decompose complex materials in dead organism into simpler substances to obtain food and release nutrients back into ecosystem
What is biomass
Total mass of living materials present at a particular time and place withing certain organisms ( gm-2/gm-3)
Worked out by
Heat biomass sample until mass is constant
Weigh dry mass
Burn dry mass in calorimeter
Measure volume and temperature change of surrounding water
What are gpp and npp
Gross primary production- total amount of solar energy plants convert to organi. Matter stored as chemical energy within their biomass
Net primary production- chemical energy available to next trophic level after respiratory losses (energy that is converted to biomass)
What are key features of nitrogen cycle
Ammonification- converts organic nitrogrn compounds in dead organisms to ammonia/ammonium. Death or excretion products broken down by saprobionts
Nitrification- creation of nitrate and nitrite from ammonia
Denitrification- conversion back to nitrogen. Depletes soil nitrogen, anaerobic conditions
What are key bacteria involved in nitrogen cycle
Rhizobium- fixes N2 to NH3, converted into amino acids for plant and plant supplies carbohydrates
Azotobacter- fixes N2 to NH3 decomposed by saprobionts, releasing nitrogen rich compounds
Nitrosommonas- converts ammonia to nitrites
Nitrobacter- converts nitrites to nitrates
What are the different types of succession
Primady- occurs in habitats of new exposed or formed land with no organic material
Secondary- occurs in areas with preexisting community which was removed leaving soil
What is the process of succession
Initial colonisation of pioneer species. Can cope with extreme initial conditions,like lichen or moss.
Pioneer species alter conditions by contributing organic matter helping soil formation creating a layer of humus
Intermediate communities are able to settle and continue to modify the environment
Intermediate communities diversify as a higher variety of species occur and biomass grows, larger and more complex organisms arrive
Climax community is formed stable ecosystem with a balanced equilibrium of species, small number of dominant species which h are rarely replaced.
What is deflected succession
When human activity interrupts natural sequence preventing natural climax, instead a plagioclimax is reached. Caused by overgrowing and trampling
