populations and ecosystems Flashcards
what is meant by the carrying capacity
the maximum population size that can be supported by the environment.
what are fugitive species
high reproductive and dispersal rate and poor competition.
what are equilibrium species
control population within a stable habitat-shown on a sigmoidal growth curve.
What happens in the lag phase of a population curve
Period of adaptation or preparation for growth and time for sexual maturity.
What happens in the exponential phase of a population curve
Population increase
As nimbers increase more become available for reproduction as long as no limiting factor effects growth.
The rate cannot be maintained indefinitely because of environmental resistance.
What happens in the stationary phase of a population growth curve
Birth rate equal to death rate
Population reached carrying capacity.
Death phase can then occur e.g for bacteria this could be beacuse of toxic waste.
What are density dependent factors
The more dense a population the bigger the effect usually biotic factors.
What are density independent factors
Factors effecting an individual regardless of population such as temp
Whay is the carbon footprint
Total amount of carbon dioxide attributable to the actions of an individual or product over a year
What does nitrogen have to be converted to to be able to be used by plant
Ammonium or nitrate ions
Name some nitrogen containing compounds that is passed through the cycle
Amino acids
ATP
Bases
Chlorophyll
What happens in nitrification
Ammonium ions oxidised to nitrites by nitrosomonas. Nitrates are then oxidised to nitrates by nitrobacter
What is the chemical formula for nitrates
NO3-
What is the chemical formula for nitrites
NO2-
What happens in nitrogen fixation
An enzyme in some bacteria combines N2 and hydrogen to form ammonia.
Ammonia can be combined with organic acods to form bacterial protein
Azotobacter is a free living bacteroa in soil
Rhizobium live inside root nodules
How does rhizobium interact with legumes
Chemical secreted by roots attract them.
Rhizobium secretes chemicals so root grows towards them. This attraction is called chemotaxis
Bacteria infect plant roots and multiply in cortex cells. Rhizobium reveive sugars through phloem
Rhizobium uses enzymes to fix N2 to ammonia but this enzyme is inhibited by high 02 levels .
What do plants have to remove wxcess oxygen from root nodules
Leghaemoglobin to create conditions for rhizobium
What are the bacteria called that cause denitrification
Pseudomonas
What happens in denitrification
Bacteria convert nitrate ions to nitrogen gas these live in anaerobic soil.
What does the condition of souls have to be in order to be denitrified
Waterlogged and anaerobic
Name 4 ways of improving nitrogen circulation
Ploughing
Harber process
Animal waste
Planting legumes
What os the harber process
Converting nitrogen to fertilisers
What is eutrophication
Artificial enrichment of aquatic habitats caused by fertiliser dun off and disrupts equilibrium of minerals
What are some legislations to minimise eutrophication
Restrict amount of fertiliser added to soil
Only apply when crops are actively growing
Leave at least a 10 m strip to next watercoarse
Dig drainage ditches which can create home to unusual species due to conditions
What is the gross primary production
Total amount fixed for photosynthesis
What is net primary productivity
How much energy is available for the primary consumers that eat a plant
What is the equation for net primary productivity
NPP=GPP-R
R= respiratory loss
