Ecology

Definitions

Population - the total number of a single interbreeding species in one area Community - Biotic potential - the maximum rate at which a species can reproduce given unlimited resources and ideal conditions Environmental resistance - changes to the environment to reduce and restrict the growth rate, often caused by shortages of important factors e.g. space, food Carrying capacity - the maximum population an environment can support Competition - when two or more organisms have to share resources in short supply Intraspecific - between members of the same species Interspecific - between members of different species Niche - the role of an organism in its community including its feeding habits, behaviour and its interactions with the abiotic and biotic components of its environment Mutualistic association - a relationship between two different species of organism where both gain a nutritional advantage    

Biotic - the effect of other organisms (living) e.g. competition, predators, parasites, waste Abiotic - the physical and chemical environments (non-living) e.g. temperature, water, soil Density Dependent Factors (DDP) e.g. predation, disease, parasitism, migration Density Independent Factors (DIP) e.g. earthquakes, weather, fire, pollution  

r-strategists (biotic potential) experience a 'J shaped' growth curve (boom and bust) prioritise growth rate, have high reproductive rate small size short lived poor competitors can occupy open ground more resistant to harsh conditions (pioneer species during succession) K-strategists (carrying capacity) experience an 'S shaped' growth curve prioritise stability, do not have high reproductive growth large size long lived good competitors not adapted to open ground prefer stable communities (later stages of succession)    

The Carbon Cycle            Photosynthesis Respiration Feeding Decomposition Fossilisation Combustion

The Nitrogen Cycle Decomposition Decomposers convert organic nitrogen compounds (dead organisms, excreta and faeces) into nitrates by mineralisation Ammonification Organic nitrogen compounds -> ammonia/ ammonium ions Nitrification Ammonium ions -> nitrates Nitrogen Fixation Biological Carried out by genus Rhizobium Atmospheric Lightning breaks the bonds holding the nitrogen together and these atoms then combine with oxygen in the air and nitrogen oxides are formed Denitrification Nitrates -> atmospheric nitrogen Carried out by anaerobic bacteria