ecosystems Flashcards
community
All the populations of diff species who live in some place at a given time, who can interact w/ each other
ecosystem
all interactions between the living and non-living components in a defined area
simple + complex ecosystem
Simple ecosystem = desert
Complex ecosystem = tropic rainforest
biotic
Living = influences the populations within a community
examples of biotic factors
Predation
Competition (inter-specific) for space, food, water, light etc.
Cooperation between organisms (can be between the same species or different species)
Parasitism
Disease
Camouflage
Mimicry
o A hoverfly is harmless, yet it has evolved body colouring like that of a wasp. This deters potential predators into thinking that it is a wasp and could deliver a harmful sting
abiotic factors
any physical or chemical factor (non-living) that influences the populations within a community
examples of abiotic
- Availability of water
- Light
- Temperature
- Humidity
- Atmospheric composition
- pH
- Salinity
- Soil composition
biomass
mass of living material of the organism or tissue
chemical energy that is stored within the organism or tissue
niche
Role of a particular species
How does low light intensity affect the ecosystem
Plants develop photosynthetic pigments that require less light
Grow larger leaves
Reproductive systems that only work in optimum light intensities
How does temp affect the ecosystem
Temp has the biggest effect on enzymes in the organisms that live in the ecosystem
May trigger migration/ hibernation
Dormancy/ leaf fall/ flowering in plants
Biomass can be measured in terms of:
The dry mass of an organism or tissue (in a given area)
The mass of carbon that an organism or tissue contains
The chemical energy content of the organism when burned in pure oxygen
dry mass
mass of the organism or tissue after all the water has been removed
how can biomass change
biomass of deciduous trees decreases over autumn = lose leaves
biomass sometimes given with units of time as well
shows the average biomass of an organism within a given area over that time period
How are ecosystems organised
trophic levels
Producers in an ecosystem
organism that converts light energy into chemical energy by photosynthesis
autotrophs, chemotrophs and photoautotrophs
Autotrophs
Convert energy from environment into complex organic matter, then are used as respiratory substrates or for growth
Chemo/photoautotrophs
Use light/ chemicals to convert small inorganic molecules into complex organic ones
consumers
Higher/est trophic levels
Feed on complex organic matter made by autotrophs and other organisms and use the products of digestion as respiratory substrates or for growth
why is there max trophic levels
rarely have more trophic levels than quaternary as there isn’t sufficient biomass and stored energy left to support further organisms.
Decomposers
Feed on waste or dead organsims to gain energy by digesting and respiring organic matter
Recycling - returns inorganic ions to the air/soil
Why are ecosystems dynamic
Always changing due to many interlaced intearctions that any small change causes several others–> alters flow of biomass
pyramid of numbers
pyramid of numbers good
- Easy method
pyramid of numbers bad
- No consideration of size
- Almost impossible to draw to scale
- Does not take into account seasonal
pyramids of biomass
units of biomass
- g/m2 or g/m3
limitations of pyramids of biomass
- Have to kill organism to get dry mass
- Sample small = not representative
- Does not take into account seasonal differences
units for pyramids of energy
- KJ / m2 / yr
pyramids of energy good
- More reliable – measures energy
- Allows analysis of energy transfers and losses
- Pyramid shape always same
pyramids of energy bad
- Difficulty + complex to collect energy data
ecological efficacy
efficacy with which biomass or energy is transferred from one trophic level to the next
why is a very large proportion of the suns energy not available to producers
Light falls away from plants
Light passes through leaves or is reflected away
Light is a mixture of wavelengths, and only certain wave lengths stimulate photosynthesis
why does only a small percentage of plant biomass become biomass in a primary consumer
Not all the plant’s biomass is eaten by the primary consumer - THORNS / BONES
Not all the consumer’s biomass intake is digested - faeces
primary consumer converts a lot of chemical energy to movement and heat, and only a small amount to new biomass in its own body
rough efficacy of biomass transfer
10%
formula for efficiency of biomass transfer between trophic levels
Efficiency of transfer = (biomass transferred / biomass intake) x 100
Net primary productivity (NPP)
the rate at which plants convert light energy into biomass.
Gross primary productivity (GPP
the rate at which plants convert light energy into chemical energy via photosynthesis.
Why are there fewer consumers at higher levels
Energy (biomass) is lost at each trophic level so unavailable to organism at next trophic level, therefore there’s less energy available to sustain living tissue
How is biomass lost
A
Cellular respiration - conversion to inorganic molecules such as CO2 and H2O
Excretory materials
Indigestible matter
Not everything is fit for consumption e.g. bones
Transferred at metabolic heat (movement)
Loss of biomass in endotherms vs ectotherms
Ectotherms use less energy in maintaing body heat so there is more biomass availabe
How human activities can manipulate the transfer of biomass through ecosystems
usually to maximise it in the context of maximising agricultural productivity
how can arable farmers max efficiency of transfer
Providing artificial light in greenhouses on overcast days
Optimising planting distances between crops
Irrigation to maximise growth in dry weather
Use of fertilisers
Selective breeding for fast growth
Use of fungicides/pesticides
Fencing to exclude grazers
Ploughing and herbicides to kill weeds
Plant crops that store energy in edible form e.g. seeds, fruit, tubers
how can livestock farmers max efficiency of transfer
Use of good quality feeds / food supplements
Use antibiotics and vaccines to reduce disease
Control predation with fencing or with indoor animal husbandry
Reduce competition for grazing e.g. rabbits, deer
Indoor husbandry to reduce energy loss from movement or from getting cold outside
role of nitrogen fixing bacteria
convert nitrogen gas into nitrogen containing compounds
contains the enzyme nitrogenase – combines atmospheric nitrogen with hydrogen
write out the nitrogen cycle
Nitrogen in the air is fixed via azotobacter, rhizobium or lightning
azotobacter results in nitrates in the soil which are actively transported into plants for proteins
Plants digested by animals to form animal proteins
both plant protein + animal protein released into soil by death or excretion
decomposers break these down into amino acids
ammonifying bacteria -e.g. saprobrionts – convert amino acids into ammonia
Nitrosomonas bacteria convert ammonia into nitrites
Nitrobacter converts nitrites into nitrates
Denitrifying bacteria release the nitrogen into the air and convert some back into nitrites + ammonia
rhizobium - nitrogen fixing bacteria
Mutualistic bacteria
Live in root nodules in peas + beans (leguminous plants)
Obtain carbohydrates from plants + gives amino acids to plant
azobacter - nitrogen fixing bacteria
Free living bacteria in soil
Nitrobacter
Requires oxygen
Soil with air pockets – aerated soil
Nitrite ions -> nitrate ions (highly soluble)
Oxidation
draw the nitrogen cycle
Ammonifying bacteria
Saprobrionts
Come from fungi + bacteria kingdoms
Extracellular digestion of DOM= saprobiotic nutrition
Releases nitrogen-containing compounds into the soil
Carries out ammonification
nitrifying bacteria
nitrosomonas
nitrobacter
when does denitrifying bacteria occur
Occurs when soil becomes waterlogged – short of oxygen
draw out the carbon cycle
Nitrosomonas bacteria
Get energy from reactions involving inorganic ions
Ammonium ions -> nitrite ions
Oxidation + releases energy
Requires oxygen
what carries out denitrification + what are its effects
Anaerobic bacteria
Soil nitrates -> nitrogen in atmosphere
Uses nitrates in respiration – releasing nitrogen gas
carbon stores
In the atmosphere (as CO2)
In sedimentary rocks
In fossil fuels like coal, oil, and gas; coal is almost pure carbon
In soil and other organic matter
In vegetation (e.g. as cellulose)
Dissolved in the oceans (as CO2)
Photosynthesis
Autotrophs – fix carbon dioxide
Removes from atmosphere
sedimentation
Plants that die – not fully decomposed
Bodies form layers of sediment + lock carbon into ground
Aquatic organisms – form sediments on sea bed – form fossil fuels
physical and chemical effects in the cycling of carbon within ecosystems
Succession
ecosystem changes from simple to complex
each stage in succession
seral stage
Primary succession
process that occurs when newly formed or newly exposed land is gradually colonised by an increasing number of species
describe primary succession
Seeds + spores carried by wind land on exposed rock + begin to grow
Pioneer species change abiotic conditions – less hostile
die + decompose DOM / humus – form basic soil
Break apart top surface of rock
Fragmented rock + humus broken down – basic soil
Seeds of small plants / grasses – carried by wind/ bird faeces land on basic soil + grow
Secondary colonisers
adapted to survive in shallow / nutrient-poor soils
these die + decompose - new soil deeper / more nutrient-rich
lichens cant grow on soil – die out
roots of these form a network that helps to hold the soil in place + prevent it from being washed away
Larger plants and shrubs + small trees = require nutrient-rich soil now grow
more water, which can be stored in deeper soils – ferns
final species to colonise the new land
complex ecosystem
outcompete shrubs / smaller plants for light
climax community
Pioneer species
Species that begin the process of succession, often colonising an area as the first living thing there
lichens
adaptations of pioneer species
adaptations
produce large number of seeds + spores
seeds that germinate rapidly
ability to photosynthesis
tolerance to extreme environments
ability to fix nitrogen from air – add to mineral content of soil
Climax community
Final, stable community that exists after the process of succession has occurred
Usually woodland communities
secondary succession
Does not start from bare ground
Takes place on a previously colonised but damaged/disturbed habitat
Why are sand dunes helpful in terms of succession
Shows us the stages of succession in order of occurrence whereas usually we only see the current stage
How does succession affect species diversity
Increases it however dominant species may outcompete the smaller species killing whole species off
How does weathering contribute to succession
Decomposition of rock increases soil depth/ changes soil composition
Favouring new species
- Gross primary productivity (GPP)
the rate at which plants convert light energy into chemical energy via photosynthesis.
NPP equation
Therefore: NPP = GPP – R
R = respitory losses
The net productivity of consumers can be calculated using the following equation
N = I - (F + R)
Where:
I = the chemical energy store in ingested food
F = the chemical energy lost to the environment in faeces and urine
R = the respiratory losses to the environment
deflected succession
activity of humans by which the resulting stable community is different to the climax community that would have occurred via natural selection
Plagioclimax
Sub-climax community when succession has been deflected
Ways to deflect succession
Mainly agriculture and human activity e.g. Grazing
Burning
Application of fetilisers
Application to herbicide
Exposure to excessive amounts of wind
How does succession affect biomass
Increases it due to more organisms in the ecosystem
Why should sub-climax communities be conserved
Higher species diversity than climaxx communities - still contain some sub-climax species and climax species
Results in conserving a much wider range of plants and animals that dont live in the climax community
Pioneer species on sand dunes
Species that can tolerate salty water, lack of fresh water and stable sand e.g. sea rcket
Pioneer species on bare rock
Algae and lichens as they don’t need to be anchored into the soil
secondary colonisers
moss
Increasing primary productivity
Some crops are planted early
Irrigating crops
Drought resistant crops
Using greenhouses
Crop rotation
Fertilisers (provides inorganic ions)
Pesticides/ pest resistant crops
How does planting some crops early increase primary productivity
Provides a longer growing season to harvest more light
How does irrigating crops increase primary productiviy
Water is readily available for the light dependent stage of photosynthesis even when rainfall is below average
How does growing crops in a greenhouse increases primary productivity
Provides a warmer temp —> increases the rate of photosynthesis
Crop rotation
Growing a diff. crop in each field on a rotational cycle
How does crop rotation increase primary productivity
Stops reduction in soil levels of inorganic ions e.g. K^+ or NO3^-
How does use of pesticides increase primary productibity
Prevents loss of biomass and lowering yield of plant
Why do plants need NH4+
Maintains pH
Why do plants need NO3-
Part of the nitrogen cycle
Function of K+ in plants
Improves growth of leaves
Function of PO4 3- in pants
Improves growth of roots
Increasing secondary productivity
Harvesting animals before adulthood
Selctive breeding
Animals treated w/ antibiotics
Zero grazing
Keeping environmental temp constant - prevents energy loss through homeostasis
How does harvesting animals before adulthood increase secondary productivity
Minimises loss of energy as younger animals invest a larger proportion of energy into their growth
How does selective breeding increase secondary productivity
Produces improved animal breeds w/ faster growth, increased egg production and increased milk production
Zero grazing
Bringing food directly to animals
Maximises energy allocated to developing muscle by reducing need to move
Assimilation
Nitrates in the soil are absorbed from the soil by plants and algae. Animals then eat plants and assimilate nitrogen compounds too
Human activities affecting the nitrogen cycle
Use of fertiliser - neutrification, algae use up all the oxygen
Processes removing atmospheric nitrogen
Nitrogen fixation by bacteria
Atmospheric fixation
Haber process
sampling
- method of investigating the abundance and distribution of species and populations
random
positions of sampling points are due to chance
no sampling biases
systematic
sampling points chosen
possible bias
unrepresentative
sampling method to estimate size of population
Quadrats - for non-motile or slow-moving species
Transects - for non-motile or slow-moving species
Mark-release-recapture - for motile species
Species frequency
probability that species will be found within any quadrat in the sample area
number of quadrats that the species was present in is divided by the total number of quadrats and then multiplied by 100
calculate percentage cover
transects
show how the distribution or abundance of a species changes with the different physical conditions in the area
mark-release capture method
large first sample taken
marked – not in a way that will effect survival
returned to habitat.
After time – another large sample captures
Count number of marked + unmarked
mark-release capture equation
Assumptions - mark capture release
marked individuals are given sufficient time to disperse and mix back in fully with the main population
marking doesn’t affect the survival rates of the marked individuals
marking remains visible throughout the sampling and doesn’t rub off
population stays the same size during the study period
there are no significant changes in population size due to births and deaths
there are no migrations into or out of the main population
Deciding how many samples to take
In a pilot study take random samples looking at species distribution
Plot quadrat number against cumulative frequency
When curve levels off use that number of quadrats
