populations Flashcards
what is the carbon cycle important for?
formation of complex organic molecules
what are the carbon stores?
oceans (dissolved in carbonate salts)
sediments e.g. limestone
fossil fuels
biomass
atmosphere
what happens to carbon during photosynthesis?
CO2 is removed from atmosphere by terrestrial plants
removed from ocean stores by aquatic plants
what happens to carbon during respiration?
CO2 is returned to the carbon stores in air and oceans
what happens to carbon during decomposition?
CO2 is released from dead organisms by saprotrophs
what happens to carbon during fossilisation?
formation of fossil fuels from dead ogranisms which have not decayed
formation of limestone
what happens to carbon during combustion?
carbon from fossil fuels returned to atmosphere
what is the greenhouse effect?
greenhouse gases let suns short wave radiation reach earth but trap some long wave radiation coming from warm earth
what are the main reasons for enhanced greenhouse effect?
burning fossil fuels
deforestation
methane increase due to rice crops, cattle and rotting materials in landfill
CFC’s
what are the consequences of global warming?
melting of polar ice caps
thermal expansion of water
increased frequency of droughts/hurricanes/forest fires
effects food production
habitat changes cause disruption of species
what is carbon footprint?
the total amount of CO2 attributable to the actions of an individual in the course of one year
what is the impact of agriculture fertilisers?
large amounts of nitrogen rich fertilisers needed for high yielding crops (NPK/manure)
if too much used or used before rainfall nitrates can leach into lakes and rivers causing eutrophication
what happens during eutrophication?
nitrates washed out of of soil (leaching)
nitrates in water cause rapid growth of algae
dense algal growth blocks out sunlight to submerged plants
plants and algae die
broken down bysaprotrophs that use up all O2
cause aquatic organisms to die
how does man affect nitrogen cycle?
ploughing soil increases O2 content
installing drainage systems
both encourage growth of nitrifying bacteria
lead to leaching
measures to reduce mans affect on nitrogen cycle?
restrict amount of fertilisers
crop rotation
avoid ploughing up established grassland
what is the nitrogen cycle?
the flow of inorganic and organic nitrogen containing compounds within abiotic and biotic compounds of an ecosystem
what is nitrogen needed for?
needed for making amino acids/proteins/ATP/nucleic acids
what is nitrogen fixation?
where nitrogen molecules found in atmosphere combine with other atoms
gets fixed when combined with oxygen or hydrogen
what are ways in which nitrogen can be fixed?
atmospheric fixation (lightening)
industrial fixation
biological fixation (free living and symbiotic relationship bacteria)
what is nitrification?
ammonium ions are oxidised into nitrite ions by nitrosomonas
nitrite ions are oxidised into nitrate ions by nitrobacter
what is the process by which ammonium ions are oxidised into nitrite ions?
nitrosomonas
what is the process by which nitrite ions are oxidised into nitrate ions?
nitrobacter
how do nitrate ions get into plants?
absorbed by plants and assimilated into organic nitrogen-containing molecules
what is ammonification?
decomposition by bacteria and fungi
detritivores break down amino acids from dead animals and plants, faeces and urine into ammonium ions
what is denitrification?
nitrate ions are reduced back into nitrogen gas
usually in water logged soil with anaerobic conditions
what is the rough cycle?
nitrogen fixing + decomposers make ammonium ions in soil
ammonium ions
nitrite ions
nitrate ions
absorbed by plants or denitrification back into atmosphere
animals and plants decay
repeat
what do free living bacteria do in soil?
have ability to combine nitrogen gas to form ammonium ions
what do symbiotic relationship bacteria do?
love in root nodules of legumes
nitrogen reduced to ammonium ions by nitrogenase
nodules contain haemoglobin which binds to oxygen to create oxygen free environment for enzyme to function in
what is an ecosystem?
a balanced biological system where all organisms and the non-living components interact in a particular location
what is a habitat?
place where an organism lives
what is a niche?
role and position of an organism within its environment including all interactions with biotic and abiotic factors in its environment
what are limiting factors?
aspects of environment which restrict population size
what are species?
group of organisms which share a large number of common characteristics and which can interbreed to produce FERTILE offspring
what is a population?
a group of organisms of a single species interbreeding and occupying a particular habitat
what is a community?
interacting populations of two r more species in the same habitat at the same time
what are factors affecting population size?
birth rate
death rate
immigration/emigration
what term should you use instead of birth rate for animals which aren’t mammals?
reproductive rate
what are the phases of animal population?
lag phase
log phase
stationary phase
what happens in the lag phase (animals)?
slow growth due to shortage of reproducing individuals
adaption to environment
what happens in the log phase (animals)?
fastest population growth
birth rate > death rate
plentiful resources
no limiting factors
what happens in the stationary phase (animals)?
birth rate and death rate are balanced
environmental resistance
what are the phases of bacterial/yeast population?
lag phase
exponential phase
stationary phase
death phase
what happens in the lag phase (bacteria)?
bacteria are synthesizing new enzymes and proteins
rate of cell division is slow
what happens in the exponential phase (bacteria)?
no other limiting factors
cells divide at max rate
what happens in the stationary phase (bacteria)?
cells are dying at the same rate that they are reproducing
limiting factors
what happens in the death phase (bacteria)?
cell death is greater than rate of production of new cells
build up of toxic waste
what is the carrying capacity?
max population size that can be sustained over a period of time in a particular habitat
maximum number around which a population fluctuates about this set point in a given environment
what is environmental resistance?
environmental factors that slow down population growth
combined effects of limiting factors that prevent further increase in population
what are the limiting factors of population in bacterial culture?
available food
overcrowding
competition
accumulation of toxic waste
what are the limiting factors of population of animals/plants?
predation
disease
parasitism
competition
light intensity
water availability
soil pH
what are density dependent factors?
affect a higher proportion of population if the population is denser
e.g. predation, disease, food availability, toxic waste, competition
what are density independent factors?
effect of these factors do not depend on population size, all members of species are equally effected
e.g. sudden violent change in abiotic factor
what do plants/animals compete for?
light
water
nutrients
space
shelter
reproductive mates
what is INTRAspecific competition?
competition between individuals of same species
density dependent
what is INTERspecific competition?
competition between individuals of different species
two species cannot occupy the same niche in a specific habitat
what is niche separation?
two species avoid competition with each other
niche overlap avoidance
what is the generalized predator-prey cycle?
predator pop increases as more prey available
number of prey decreases due to more predators hunting
number of predators now decreases as less prey to eat
repeat
what is abundance?
number of individuals in a given area or volume
what is distribution?
area or volume in which organisms of species are found
how can you calculate plant abundance?
Quadra method
line transect
how can you calculate animal abundance?
kick sampling in stream
capture-mark-recapture method
what are the assumptions of the capture-mark-recapture method?
no emigration/immigration
no births or deaths during experimental period
marked individuals distribute themselves evenly throughout population
marking process is non-toxic / does not make population more susceptible to predation
what are the limitations of kick sampling?
difficult to identify species
difficult to count total number of species
numerous very small species collected
may count more than once as animals will move
what is succession?
change in structure and composition of species in a community over time
replacement of one species by another through time as environment changes or as better adapted species arrives
what are pioneer species?
first plants to grow in a new habitat
often highly adapted to a very harsh environment
what are lichens?
slow growing symbiotic relationship between fungi and algae
what are mosses?
able to root into the first soil by decomposing lichen
could not survive on bare rock alone
what is the grassland community?
decomposing moss and lichen establishes soil sufficient for roots of low growing herbaceous plants and grasses
seeds blown by wind into habitat establish grassland
what are shrubs?
more perennials woody plants outcompete grasses and block sunlight
what happens during the climax community?
dominated by trees a wide variety of both plants and animals growing at a variety of both plants and animals growing at a variety of heights
what are the seral stages / seres?
different stages in a succession when particular communities dominate between the pioneers and the climax
what is a climax community?
final stage of succession in which the species composition remains relatively stable
community has reached equilibrium
what are the gradual changes during succession?
soil becomes deeper and contains more minerals
number of woody plants increases
biodiversity and stability of community increases
pioneer plants are usually lost
what is secondary succession?
repopulation of an area that has been previously colonized, often due to the habitat being disturbed/damaged
why is secondary succession quicker than primary?
already an existing seed bank in soil
root systems undisturbed in soil
fertility and structure of soil has already been substantially modified by previous organisms to make it more suitable for growth
what are factors affecting succession?
migration of species (needs arrival of seeds)
interspecific competition
facilitation
what are the sources of energy for ecosystems?
sun
from chemical reactions
what are food chains?
a means of transferring biomass
what is biomass?
mass of biological material in living or recently living organisms
what happens in food chains?
suns energy and inorganic compounds are incorporated into carbohydrates by photosynthesis
each group operates at trophic level
energy passes to higher trophic level
energy in food consumed is incorporated into molecules of consumer
as energy is passed alone food chain there is a loss of energy between each level
what do food chains not show?
all species at each trophic level
detritivores and decomposers
omnivores or organisms
what percentage of biomass at each trophic level is passed on to the next level?
10%
what is gross ecological efficiency?
the percentage transfer of energy from one trophic level to the next
what is photosynthetic efficiency?
a measure of how well a plant is able to capture light energy
how can you calculate photosynthetic efficiency?
quantity of light energy incorporated in products / quantity of energy falling on plant
x 100
what is the typical value for photosynthetic efficiency?
1-2%
why is typical value for photosynthetic efficiency so low?
sunlight missing plant
light that does hit leaf is reflected from leaves / passes through leaves / absorbed by non-photosynthetic plants
what is gross primary productivity (GPP)?
rate of production of chemical energy in organic molecules by photosynthesis in a given area and time
what is net primary productivity (NPP)?
potential food available to primary consumers
energy in plant biomass
how can you calculate NPP?
GPP - R (respiration)
why is energy lost between trophic levels?
not all of tissue is eaten (bones)
indigestible tissue consumed so passes out in faces
food is respired to provide energy for active transport / muscle contraction / keeping warm
energy lost in excretory products
why are herbivores less efficient than carnivores?
cellulose is much more difficult to digest than protein
much more energy is left in faces
a lot more energy is used during digestive process
what is secondary productivity?
rate at which consumers accumulate energy in the form of cells or tissues
how can you calculate efficiency of energy transfer?
energy incorporated in biomass after transfer / energy available in biomass before transfer
what are the advantages and disadvantages of pyramid of numbers?
easy to construct
levels in pyramid simply show number of organisms
doesn’t take into account size of organism
what are the advantages and disadvantages of pyramid of biomass?
slightly more accurate as biomass is involved
difficult to measure
does not take into account life span
what are the advantages and disadvantages of pyramid of energy?
most accurate way
shows energy transferred from one trophic level to the next
what is a standing crop?
mass of individuals present at a given time
