ch4: peat my beloved Flashcards
define species, habitat, population, community, ecosystem (5)
habitat: the environment in which a species normally lives
population: a group of organisms of the same species who live in the same area at the same time
community: a group of species living & interacting with each other in an area
ecosystem: a community & its abiotic environment
species: group of organisms that can interbreed to produce fertile offspring
describe what is meant by a food chain and a food web (6)
food chain: shows transfer of energy in an ecosystem between different trophic levels
e.g. green algae → mayfly larvae → juvenile trout → kingfisher
food web: branched interaction of multiple food chains
transferring energy to consumers from different food chains
same consumer could be at different trophic levels in a food web
outline the role of decomposers in recycling nutrients (2)
digest/absorb dead organic matter
detritivores: ingest dead organic matter
saprotrophs: secrete enzymes onto dead organic matter
produce inorganic nutrients → assimilated by living organisms
e.g. bacteria/fungi
outline how these phosphate and nitrate ions are used in the synthesis of organic molecules (3)
phosphates used to make phospholipids/nucleotides
nitrates are used to make amino acids/proteins/nucleotides
attached to carbon compounds
transported from roots to leaves in xylem
photosynthesis provide energy for the synthesis of these compounds
distinguish between autotrophs and heterotrophs (2)
autotrophs make their own organic matter: require inorganic molecules
heterotrophs feed on organic molecules from other organisms: require complex organic molecules
outline the features of ecosystems that make them sustainable (4)
recycling of nutrients
e.g. carbon & nitrogen
decomposers break down organic matter & release inorganic nutrients
energy lost from ecosystems as heat → cannot be recycled → ongoing supply is needed from the sun
energy flow along food chains thru trophic levels
autotrophs make food by photosynthesis
release oxygen for aerobic respiration
carbon dioxide for photosynthesis released by respiration
populations limited by food supply: regulated by neg feedback
supplies of water from rainfall: water cycle
outline the energy flow between trophic levels in a food chain (6)
light is the initial energy source for food chains
autotrophs convert light energy into chem energy thru photosynthesis to make glucose
energy flows through food chain by consumption
moves up trophic levels
producers → primary consumers → secondary consumers → tertiary consumers → detritivores/saprophytes/decomposers
energy conversions are inefficient energy lost in the form of heat by respiration in undigested food through the death of organisms only 10-20% is passed to next trophic level energy is not recycled in an ecosystem: only nutrients are
describe what is shown in pyramids of energy (6)
show flow of energy from one trophic level to the next in a community
1st trophic level: producers
2nd trophic level: primary consumer
3rd trophic level: secondary consumers
bar width is proportional to energy stored in biomass in that trophic level
decreases proportionally as you go up each level
only 10-20% of energy of 1 level is passed to the next
limit the length of food chains
units are kJ m-2 yr-1
explain, using an example of a food chain, how trophic levels can be deduced (4)
e.g. green algae → mayfly larvae → juvenile trout → kingfisher
trophic level = position of an organism in the flow of energy thru an ecosystem
producer (1st trophic level): convert light energy into chem energy thru photosynthesis
primary consumer (2nd trophic level): feeds on producers
secondary consumer (3rd trophic level): feeds on primary consumers
observe which organisms eat each other
explain why populations that have grown exponentially reach a maximum size, rather than continue to grow (7)
during exponential growth, population has few limitations
plateau phase = max sustainable size
occurs as limitations ↓ growth
population has reached carrying capacity
further population growth limited by abiotic factors
temp, climate, weather, seasons
lack of water & food supply
destruction of breeding habitats & shelter
↑ no. of predators, competitors, enemies, diseases
population stability occurs when natality + immigration = mortality + emigration
outline the role of photosynthesis and cellular respiration in carbon cycling and energy flow in food chains (8)
nutrients are recycled
e.g. carbon cycle: some carbon fixation through fossilisation
energy is a one-way flow
depends on a constant supply of energy from the sun
only 10-20% of energy passed from 1 trophic level to the next
remaining energy released through cellular respiration
energy and carbon is passed through food chains
exothermic: cellular respiration
carbon dioxide released to atmosphere
decomposers release carbon dioxide from feeding on organic matter
endothermic: photosynthesis
carbon dioxide is fixed
light energy converted to chem energy
energy is made available to food chain
outline the roles of living organisms in the carbon cycle / Explain the cycling of carbon in an ecosystem (8)
carbon dioxide released by cell respiration of organisms
carbon pass along trophic levels
autotrophs fix carbon dioxide from atmosphere in photosynthesis to produce organic compounds
eaten by primary consumers → carbon compounds digested and absorbed
primary consumers eaten by secondary consumers
plants & animals die → decomposed by saprotrophic bacteria & fungi
combustion of fossil fuels releases carbon dioxide into the atmosphere
methane produced by methanogens in cattle
oxidised into carbon dioxide in the atmosphere
peat made from partially decomposed organic matter
volcanic eruptions add large quantities of carbon into the atmosphere
limestone are sinks of carbon
carbon cycle
discuss the processes in the carbon cycle that affect concentrations of carbon dioxide and methane in the atmosphere and the consequences for climate change (8)
CO2 is produced from respiration in organisms and combustion of fossil fuels
CO2 is converted into organic compounds by autotrophs
CO2 is converted to calcium carbonate and fossilised into limestone
combustion of fossil fuels → ↑ CO2 conc in the atmosphere → acidification of aquatic env
CH4 is produced by anaerobic respiration of biomass and methanogenic bacteria in cows
CH4 is oxidised to CO2 and water
cattle production and defrosting of tundra → ↑ CH4 in the atmosphere
decomposed organic matter can be converted into peat or fossil fuels CO2 and CH4 are both greenhouse gases longwave radiation (infrared) is absorbed by greenhouse gases and retain the heat in the atmosphere ↑ greenhouse gases → ↑ average global temp → disrupt climate patterns
describe the process of peat formation (4)
formed from dead plant material: organic matter not fully decomposed
formed in waterlogged sites where bacteria/fungi/saprotrophs are inhibited
occurs in acidic & anaerobic conditions
slow process
outline the precautionary principle, giving an example (6)
guideline for decision-making
some human-induced change can be catastrophic
applied when possible consequences are severe
a paradigm shift
those proposing must demonstrate that action will do no harm before proceeding
those opposing change do not have to prove that there will be harm
tests must be done first
activities that may cause harm are banned
e.g. consequences of building a dam on a river determined b4 it is built
explain how the process of photosynthesis affects carbon dioxide concentrations in the atmosphere during a typical year and the likely consequences on Earth of the yearly rises in carbon dioxide concentrations (8)
photosynthesis fixes carbon dioxide into organic molecules → ↓ carbon dioxide level in atmosphere
annual fluctuations of carbon dioxide levels related to photosynthesis
↑ photosynthesis during spring & summer due to longer day time
consequences: enhanced greenhouse effect caused by ↑ carbon dioxide → global warming rising ocean levels/melting of glaciers changes in weather patterns ocean acidification alter food webs loss of habitat changes in distribution of plants and animals → extinction
outline the causes and consequences of the enhanced greenhouse effect (5)
causes:
burning of fuels → release carbon dioxide
deforestation → ↓ carbon dioxide uptake
methane emitted from cattle
consequences:
global warming
melting of glaciers → rising ocean levels
↑ decomposition rates
loss of habitat
changes in distribution of plants and animals → extinction
explain the relationship between rises in concentration of atmospheric gases and the enhanced greenhouse effect (8)
greenhouse gases: water vapour, carbon dioxide, methane, nitrogen oxides
all gases occur naturally
human activity ↑ the normal level of these gases in recent years
shortwave radiation (light) from the Sun enters atmosphere → pass through greenhouse gases → some absorbed and warms Earth’s surface some is re-radiated by the surface of the Earth as longwave radiation (infrared) → absorbed by greenhouse gases and retain the heat in the atmosphere ↑ the atmospheric temp at higher rate than normal → creating a pos imbalance → threatens ecosystems
Earth’s history has many fluctuations in gas levels
some scientists are skeptical about enhanced greenhouse effect
explain how the emission of gases, both naturally and through human activity, can alter the surface temperature of the Earth (8)
global warming = ↑ in temp caused by the greenhouse effect
a natural phenomenon that has occurred over millions of years
main gas responsible is carbon dioxide
other gases like methane/nitrous oxide also cause effect
shortwave radiation (light) from the Sun enters atmosphere → pass through greenhouse gases → some absorbed and warms Earth’s surface some is re-radiated by the surface of the Earth as longwave radiation (infrared) → absorbed by greenhouse gases and retain the heat in the atmosphere
rapid rise in temperatures over a hundred years
combustion of fossil fuels releases carbon dioxide into the atmosphere
CH4 is produced by peat and methanogenic bacteria in cows
volcanic eruptions add large quantities of carbon into the atmosphere
explain X, Y and Z on the diagram (4)
X: UV
Y: infrared
Z: presence of greenhouse gases
IR absorbed and re-radiated to heat the earth
outline three possible consequences of global warming for organisms living in arctic ecosystems (3)
reduced habitat for ice-dwelling species
change in patterns of migration: arctic species forced to migrate
↑ competition from temperate species
changes in distribution of prey
↑ activity of decomposers
↑ success of pest species and pathogens
evolution: extinction of some species due to inability to adapt/compete successfully
suggest how climate change can influence the natural selection of Arctic organisms (3)
individuals in a population will show a variation of adaptations to climate change
e.g. polar bears have less ice to catch prey → starts fishing in rivers in Quebec
organisms that resist temperature changes will survive better
reproduce more and pass on their characteristics
organisms with less adaptations will disappear with time
changes will occur within species → new species may appear over time
