6.3.1 - ecosystems Flashcards
ecosystem
made up of all the living and non living parts, all interacting together
biotic factors
living factors
e.g animals, plants, competition, pathogens
abiotic factors
non living or physical factors, e.g rainfall, or temperature range
soil factors
clay - fine particles and easily waterlogged
loam - different sized particles, no waterlogging
sandy - course particles - does not retain water
trophic level
each stage in the food chain
producer
organism that converts light energy into chemical energy by the process of photosynethsis.
consumers
organisms that obrain their energy by feeding on other organism
decomposer
break down dead organisms releasing nutrients back into the ecosystem
biomass
mass of living material present in a particular place or in a particular organism
how to work out the biomass at each trophic level
multiply the biomass present in each organism by the total number of organisms in that trophic level
ecological efficiency
the efficiency with which biomass or energy is transferred from one trophic level to the next
how much sunlight do producers convert into chemical energy
1-3%
why is only a small amount of energy converted in producer transfer?
- not all solar energy is used for photosynthesis - around 90% is reflected
- other factors may limit photosynthesis
- proportion is lost, as it is used for photosynthetic reactions
gross production
total solar energy that plants convert to organic matter
net production formula
net production = gross production - respiratory losses
efficiency at consumer level and why?
10% of the biomass is converted
- not all biomass is eaten
- some energy is transferred to the environment as metabolic heat
- some parts are eaten but are indigestable
- some energy is lost as excretory maaterials
agriculture
manipulating the environment to favour plant species to eat or rear animals for their produce.
what conditions are needed for agriculture?
abiotic conditions they need to survive - watering and warmth
competition is removed
predators are removed
why are the food chains in agriculture so small?
minimum energy is lost - as much energy as possible is transferred into biomass that can be eaten by humans
decomposition
a chemical process in which a compound is broken down into smaller molecules or its constituent elements.
saprotrophs
obtain their energy from dead or waste organic material, digesting their food externally by secreting enzymes into dead organisms or organic waste matter
detritivores
another class of organism involved in decomposition. help to speed up the decay process by feeding on detritus, breaking it down into smaller pieces of organic material, increasing the surface area for decomposers to work on
why is nitrogen essential
amini acids and nucleic acid production in plants and animals
nitrogen fixing bacteria
azobacter and rhizobium contain the enzyme nitrogenase
nitrogen fixation
combines atmospheric nitrogen with hydrogen to produce ammonia
symbiotic mutualistic relationship between nigtrogen fixing bacteria and the plant
- plants gain amino acids from Rhizobium produced during nitrogen fixation
- bacteria gain carbohydrates produced by the plant during photosynthesis
nitrification
process by which ammonium compounds in te soil are converted into nitrogen containing molecules that can be used by plants
two steps of nitrification
- nitrifying bacteria oxidise ammonium compounds into nitrites
- nitrobacter oxidise nitrites into nitrates
denitrification
converting nitrates back into nitrogen gas - only takes place under anaerobic conditions
ammonification
name given to the process by which decomposers convert nitrogen containing molecules in dead organisms into ammonium compounds
processes of the nitrogen cycle
nitrogen fixation, nitrification, denitrification, ammonification
why is carbon essential?
present in all living organisms, such as fats, carbohydrates and proteins
processes in the carbon cycle
photosynthesis, respiration, combustion, feeding, decomposition
why do co2 levels fluctuate throughout the day?
photosynthesis only takes place in the light, and so during the day photosynthesis removes co2 from the atmosphere - respiration takes place at all times so co2 is always released
co2 levels are higher at night
why have co2 levels increased over the past 200 years?
- combustion of fossil fuels
- deforestation
succession
the process by which ecosystems change over time, occuring as a result of changes to the environment
primary succession
area of land which is newly formed or exposed, such as bare rock - no soil or organic material present to begin with
secondary succession
occurs on areas of land where soil is present but contains no plant or animal species
when does primary succession occur?
- volcanic eruptions, depositing lava
- sand is blown by the wind to create sand dunes
- slit and mud are deposited at river estuaries
pioneer species
begin the colonisation of an inhospitable environment by organisms, arriving by spores or seeds carried by the wind
pioneer species adaptations
- ability to produce large quantities of spores or seeds
- seeds that germinate rapidly
- ability to photosynthesise to produce their own energy
- tolerance to extreme environments
- ability to fix nitrogen from the atmosphere
how do the pioneer species make the environment inhabitable?
when they die and decomopers small organic products are deposited into the soil - known as humus, which then makes the soil able to support the growth of new species of plants
example of a secondary coloniser
mosses
example of a tertiary coloniser
ferns - usually xerophytes
climax community
stable state- will show very little change over time, biodiversity is not very high
deflected succession
human activities halting the natural flow of succession and preventing an ecosystem from reaching a climax community.
pagioclimax
the final stage in deflected succession
examples of agriculture causing deflected succession
- grazing and trampling of vegetation by domesticated animals
- removing existing vegetation to plant crops
- burning as a means of forest clearance
distribution
refers to where individual organisms are found within an ecosystem
abundance
refers to the number of individuals of a species present in an area at any given time
what actions are taken by farmers to increase productivity and efficiency?
treating animals with antibiotics to reduce energy loss from illness
select for animals with fastest possible growth rate
outline how fungi lead to the availability of nitrogen compounds in the ecosystem
- saprobionts digest large nitrogen containing polymers such as proteins and nucleic acids
- enzymes secreted by fungi to break down proteins, containing nitrogeneous amino acids
- amine groups split from amino acids to form ammonia ions
describe the similarities between the nitrogen and carbon cycle
- organic gases in atmosphere
- elements fixed to organic compounds
- incorportaed into plants and animals
- animals obtain element by feeding on plants
- decomposing microorganisms
- releasing inorganic molecules
microorganisms return element to atmosphere
descrive how atmospheric nitrogen can become part of a protein in a herbivore
- N2 can be fixed by nitrogen fixing bacteria
- bacteria may live inside the roots of a plant (symbiotic relationship)
- plants with nirogen fixing bactrtia will die and drop leaves, releasng proteins
- these are broken down by decomposing bactera, and converted into ammonia
- nitrifying bacteris convert ammonia into nitrite and nitrate ions
- absorb ions through root systems
- amino acids absorbed by cells in digestive systems and are used to develop bew proteins
