ecosystems - MODULE 6 Flashcards
Nitrogen fixation
what happens
what bacteria
Nitrogen (N2) and 3Hydrogen (3H2) react together to form Ammonia (2NH3). Can be carried out by nirogen fixing bacteria (Rhizobium and Azotobacter(Using enzyme Nitrogenase)), lightning and the Haber process
Ammonification
Nitrogen compounds (NO3-) from dead organisms and nitrogenous waste (urine) are turned into ammonium (NH4+) by decomposers (mainly fungi and bacteria). The ammonium can then converted into ammonia
Nitrification
opposite of Ammonification
The oxidation of ammonium ions (NH4+)into Nitrites(NO2+) and then Nitrates(NO3-). Carried out by Nitrosomonas and* Nitrobacter*)
Denitrification
Denitrifying bacteria convert nitrates (NO3-) back into nitrogen gas (N2) under anaerobic conditions by Pseudomonas
bacteria use nitrates as a source of energy for respiration. Nitrogen is released
what is an ecosystem
all the organisms living in a certain area and all the non living conditions found there. both biotic and Abiotic factors
what is a biotic factor
living features of an ecosystem e.g: predators and food
what is an abiotic factor
non living features of an ecosystem
habitat
place where organism lives within a ecosystem
what is the main route that energy enters an ecosystem
photosynthesis
what are producers
plants
what is biomass
the mass of living material
order of consumers
PRoducer eaten by primary - > secondary - >tertiary consumer
what is a trophic level
a stage in a food chain that’s occupied by a particular group of organisms e.g: producers are the first trophic level
what is gross productivity
the rest of the available energy (40%) that is taken after rest is lost by previous trophic level q
what is respiratory loss
30% of total energy availiable is lost to environment when organisms use energy produced from respiration for movement or body heat
what is net productivity
only 10% of total energy becomes biomass.
the amount of energy that is available to the next trophic level
how to work out net productivity
= gross productivity - respiratory loss
Efficiency of energy transfer
net productivity of trophic level / net productivity of previous trophic level
x100
Methods of controlling energy flow thru ecosystems
Herbicides
Fungicides
Insecticides
Natural predators
Fertilisers
Rearing livestock intensively (limit activity)
components to carbon cycle
Photosynthesis
Decomposition
Respiration
Combustion
Release from volcanoes
Weathering
Release from and absorption into the ocean
what is weathering in the carbon cycle
Rocks containing CArbon can eventually become land. THis is then weathered (broken down by exposure to the atmosphere). This can happen chemically by rain water. and physically by animals and plant roots etc.
what is Release from and absorption into the ocean in the carbon cycle
CO2 can also dissolve directly into oceans from the atmosphere. and be transported in the ocean by deep underwater currents. CO2 can remain in these slow-moving currents for hundreds of years before returning to the surface and being released back into the atmosphere
Azotobacter
free-living soil bacterium nitrogen fixating bacteria
Rhizobium
live inside root Nodules of leguminous plans such as peas ..
Nitrogen fixating bacteria
Nitrifying bacteria do
e.g
(e.g: nitrosomonas + nitrobacter) oxidise ammonium compounds into nitrites
Nitrobacter do
oxidise nitrites into nitrates
what processes are involved in the Nitrogen cycle
-Nitrogen fixation (N2 into Ammonia, mutualistic + free living)
-Nitrification (ammonium into nitrites)
-absorption (of ammonium and nitrates into plants)
-Feeding (tertiary consumers eat producers)
-Ammonification (decomposition of dead plants producing Ammonium ions by saprobionts)
-Denitrification (Nitrate into N2 in air)
what are the two types of successtion
-primary
secondary
what is secondary succession
occours on areas of land where soil is present, but it contains no plant or animal species
e.g: bare earth that appears affter a forest fire
what is primary succession
occurs on an area of land that has been newly formed or exposed such as bare rock . no soil or organic material to begin with
what are the stages of succession called
seral stage
summary of a pioneer community
colonisers e.g: lichen + algae
components of a Intermediate community
e.g:
secondary colonisers e.g: mosses
tertiary colonisers e.g: grasses
Scrubland e.g: shrubs and small trees
summary of a climax community
Dominant species e.g: woodland
what is humus
the organic component of soil from dead decomposed pioneer species
when is biodiversity usually the highest during succesion
mid-succession due to later more dominant species wiping out others in later stages as they put compete them
Deflected succession
Human activities can halt the natural flow of succession and prevent the ecosystem from reaching its climax community
plagioclimax
when succession is stopped artifically, the final stage is plagioclimax
- The nitrogen cycle shares many similarities with the carbon cycle.
Describe the similarities between the nitrogen cycle and the carbon cycle
- inorganic gases
o CO2 and N2 - in atmosphere
- elements fixed to organic compounds
o C and N both form proteins /
nucleic acids - incorporated into plants (producers) then
animals (consumers) - animals obtain element by feeding on
plants - decomposing microorganisms
- break down organic macromolecules in
living things - release inorganic molecules
o carbon dioxide and ammonium
ions - microorganisms return element to
atmosphere
o CO2 released during
decomposition
o N2 released by denitrifying bacteria
decomposer
organisms that breaks down and feeds on dead animal or plant matter, turning organic compounds into inorganic ones (nutrients) available to photosynthetic producers in the ecosystem
How is distribution of organisms within an ecosystem usually measured
plants
line or belt transect
how is a line transect used
laying a line or surveyor’s tape along the ground and taking samples at regular intervals
how is a belt transect used
Two parallel lines marked, samples taken of area between these specified points.
what type of sampling are belt and line transects
systematic sampling, a form of non-random sampling
Distribution of organisms refers to
where individual organisms are found within an ecosystem
Abundance of organisms refers to
number of individuals of a species present in an area at any given time
how is plant abundance measured
quadrats placed randomly in an area
count number of individual plants contained within the quadrat
Number of individuals in sample / Area of sample (m^2)
name how animal abundance is measured
capture-mark-release-recapture method
technique of capture-mark-release-recapture method
1)capture as many individuals as possible in a sample area
2)Mark or tag each individual
3)Release marked animals back into sample area and allow time for them to redistribute themselves throughout the habitat
4) Recapture as many individuals as possible in original sample area
5)Record number of marked and unmarked individuals present in the sample (release all individuals back into their habitat
6) use Lincoln index to estimate population size
Lincoln Index
when is it used
what is it
population size =
(no. of indivs in first sample x no. indiv in 2nd sample ) / number of recaptured marked individuals
used when doing capture-mark-release-recapture method
How to increase accuracy of a sample
- use large sample size as possible
the greater the number of individuals studies , the lower the probability that chance will influence the results
-use random sampling to reduce effects of sampling bias
why can populations rarely be counted accurately
-some animals elude recapture
-may be too time consuming to count entire population
-counting process could damage population
so sampling techniques are used*
chemical formula for nitrogen gas
N2 gas
chemical formula for ammonia
NH3
chemical formula for nitrates
NO3-
chemical formula for nitrites
NO2−
How does harvesting crops affect the Nitrogen cycle
death of plants and therefore ammonification and nitrification and absorption into plants.
Therefore, nitrate fertilisers need to be used
can result in eutrophication
where does denitrification occour
only in areas of flooding/lack of aeration
as nitrifying bacteria are anaerobic
what is nitrogen used for in plants and animals
-proteins
-DNA/RNA
-ATP
-NAD + NADP
how to calculate biomass of organisms
use calorimeter
-collect sample
-kill organism
-plance in oven at 80 C
units used for biomass of land animals vs marine animals
gm^-2
vs
gm^-3
biotic limiting factors affecting ecosystem
Disease
predation
Competition (intra + interspecific)
abiotic limiting factors affecting ecosystem
-light
-O2 availability
-H2O availability
-Temperature
-Edaphic (soil) factors (type of soil(ability to retain water) + PH)
Density independant factors limiting a population e.g:
Natural disaster
Density independant factors limiting a population e.g:
Natural disaster
