Unit 3.5 PopulationSize & Ecosystems (physics&mathstutorflashcards))
population
number of individuals (of the same species) within a given area
community
2 or more populations of (different) species within an ecosystem
habitat
the physical environment where a particular community of a population lives
environment
conditions that surround an organism (biotic+abiotic)
biotic
any living factor which affects another organism/species in any way
abiotic
non living part of the environment that can affect organisms (chemical+physical)
name 4 biotic factors
- food competition/availability
- disease
- resource/habitat competition
- predation
name 6 abiotic factors
- light intensity
- temperature
- pH
- wind+moisture
- salinity
-CO2/O2 conc
ecosystem
a dynamic biological community that is made up of biotic+abiotic components
niche
role of an organism in the ecosystem (prey/preditor)
dispersion
how geographically spaced out organisms are
fecundity
number of offspring an individual can have in a lifetime
name 4 limiting factors
- food
- temperature
- mates
- space
carrying capacity
number of individuals a habitat can sustain
growth rate =
(births - death)/original pop size
what factors alter density
births/deaths and immigration/emigration
density-dependant
effects on population size differ with population density
(larger pop = larger death rate)
density-independent
not influenced by a species population size
define ecology
the study of the relationships among organisms and their environments
what is a large ecosystem called
biome
what is a small ecosystem called
microhabitat
what do population numbers depend on
births/deaths and immigration/emigration
define birth rate
the number of offspring born per thousand of population per year
define death rate
the number of deaths per thousand of population per year
what is immigration
the number of individuals entering a region per thousand of population per year
what is emigration
the number of individuals leaving a region per thousand of population per year
when do population sizes increase
when
births + immigrants > death + emigrants
when do population sizes decrease
when
births + immigrants < death + emigrants
what are the 3 phases of population growth
- lag phase
- log phase
- stationary phase
define the Lag phase of population growth
period of slow population growth
define the Log phase of population growth
period of rapid exponential population growth in which birth rate > death rate
define the Stationary phase of population growth
period of stability in which population numbers generally remain constant
what are the axis on a graph showing bacterial population growth
side = Log of number of cells
bottom = time (hours)
what causes the carrying capacity to vary
biotic + abiotic factors
what is competition
when different organisms compete for the same resources in an ecosystem
give 3 examples of density-dependant factors
- competition
- predation
- disease
give an example of density-independant factors
- climate
define distribution
The spread of living organisms in an ecosystem
what is sampling
selecting a group of individuals that will represent the whole target population
what does sampling allow us to do
allows us to measure the distribution and abundance of organisms
suggest 2 methods of assessing abundance and distribution of organisms
- quadrats
- transects
what is a quadrat
square frames which are placed at random in an area to be investigated
what is a transect
a line/belt that runs across the area to be investigated
suggest 3 different ways that abundance can be measured
- % area cover
- % frequence
- density
what is random sampling
a sampling technique used to avoid bias
(e.g creating a square grid and generating random coordinates)
what is systematic sampling
sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals
(e.g along a belt transect)
what is the source of energy for an ecosystem
light energy
when is light not the source of energy for an ecosystem
when ecosystems rely on chemosynthesis
what is a trophic level
the position that an organism holds in a:
- food chain
- food web
- pyramid of numbers
- pyramid of biomass
what is biomass
the total dry mass of tissue
state the formula for efficiency of biomass transfer
efficiency = (biomass transferred / biomass intake) x100
why is some energy never taken in at each trophic level
- some parts of food are not consumed
- some parts of food are not digestible
- plants can not use all light energy as some is the wrong wavelength
why is some energy lost at each trophic level
respiration = lost as heat
what is a pyramid of biomass
a table of the dry mass of living material at each trophic level of a food chain
define gross primary productivity (GPP)
the chemical energy stored in plant biomass (made during photosynthesis)
measured in kJ m⁻² year⁻¹
define net primary productivity (NPP)
the amount of chemical energy that is available to heterotrophs in an ecosystem
how is NPP calculated
NPP = GPP - Respiration losses
define primary succession
where an area previously devoid of life is colonised by pioneer species
what is a pioneer species
species that can survive in hostile environments and colonise bare rock or sand
summarise the process of primary succession
- pioneer species colonise the area
- pioneer species die + decompose = nutrients are added to ground
- over time, this allows more complex organisms to survive
what are seres
various intermediate stages in succession in an ecosystem progressing towards a climax community
define secondary succession
a type of succession in which a habitat is re-colonised after a disturbance
what is a climax community
the final stage of succession, where the ecosystem is balanced and stable
how can you tell that the climax community has been reached
soil is rich enough to support large trees/shrubs and the environment is no longer changing
how does succession affect species diversity and stability of the community
succession INCREASES species diversity and the stability of the community
which 2 organisms play an important role in decay
- detritivores
- saprotrophs
what does a detritivore feed on
dead and organic matter
what does a saprotroph feed by
feeds by extracellular digestion
describe extracellular digestion by saprotrophs
release enzymes which catalyse breakdown of dead plant and animal material into simpler organic matter
what is the carbon cycle
when carbon (in form of CO₂) moves between living organisms and the environment.
involving:
- respiration
- photosynthesis
- combustion
describe the 5 stages of the carbon cycle
- plants remove CO₂ from atmosphere via photosynthesis
- eating passes carbon compounds along food chain
- respiration returns CO₂ into atmosphere
- organisms die + decompose.
saprotrophs break down dead material and release CO₂ via respiration - Combustion of materials (wood, fossil fuels) release CO₂
define global warming
the gradual rise in the average temperature of the earth due to increasing atmospheric levels of CO₂ + methane gas
define the greenhouse effect
the increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere
how might global warming affect the natural world?
- temp, rainfall, light level affect survival
- habitats may be destroyed by deforestation/flooding
- species may need to change their habitat, or face extinction
what is the nitrogen cycle
the cycle where nitrogen moves between living organisms and the environment, involving
- ammonification
- nitrification
- nitrogen fixation
- denitrification
how do plant roots take up nitrogen
taken up via active transport and facilitated diffusion as ammonium and nitrate ions
ammonium
NH4+
nitrate ions
NO3-
name the 4 types of bacteria involved in the nitrogen cycle
- nitrogen-fixing bacteria
- nitrifying bacteria
- denitrifying bacteria
- decomposers
describe ammonification
the production of ammonium compounds when decomposers feed on organic nitrogen-containing molecules
describe nitrification
the conversion of
atmospheric nitrogen gas –> ammonia
BY nitrogen-fixing bacteria in the soil/root nodules of legumes
give some examples of nitrogen-fixing bacteria
- azotobacter
- rhizobium
where does azotobacter live
freely in soil
where does rhizobium live
inside the root nodules of leguminous plants
describe nitrogen fixation
the conversion of
ammonium ions –> nitrate
BY nitrifying bacteria
what are the 2 stages of nitrogen fixation
- Ammonium ions oxidised to nitrite ions
- nitrite ions oxidised to nitrate ions
name the 2 types of nitrifying bacteria
- nitrosomonas
- nitrobacter
what is the function of nitrosomonas
oxidises ammonium compounds into nitrites
what is the function of nitrobacter
oxidises nitrites into nitrates
describe denitrification
the conversion of nitrate ions to nitrogen gas by denitrifying bacteria
what are denitrifying bacteria
anaerobic microorganisms, found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas
explain the economic importance of the nitrogen cycle
maximises plant growth and crop yield, increasing food production
name 3 methods farmers can use to increase the nitrate content of soil
- ploughing and drainage to aerate the soil
- application of fertilisers
- growing legumes
what are fertilisers
natural or artificial materials which are added to soils to provide essential nutrients and improve plant growth
Give some examples of natural fertilisers
- manure
- compost
- treated sewage
give an example of an artificial fertiliser
ammonium nitrate
what is eutrophication
pollution from nitrogen-containing fertilisers cause algal blooms and oxygen level reduction in water
describe the 7 steps of fertilisers causing eutrophication
- fertilisers run-off into rivers
- nutrients build-up in water
- algal bloom blocks sunlight
- aquatic plants cannot photosynthesis ∴ less oxygen produced
- they die+decompose
- decomposers further decrease oxygen levels
- animals can’t respire ∴ die
how does digging drainage ditches affect habitats
- habitat loss
- biodiversity reduction
- may cause eutrophication
